The solution of the examples given for the practice has been uploaded in the PDF format. drive.google.com/file/d/0B3FOmN0FcD6OWFc2OXAtcUtmcXc/view?usp=sharing&resourcekey=0-yNuVb1wrtYbtPSk9wSTHuA
wow!!! while going over this in class and reading the textbook, this topic was clear as mud. I watched this and saw how you explained these circuit analysis and I have a greater clarity on what is going on. Keep up the great work on your videos because they help a lot.
Excellent work again. I did confirm example 3 using LTspice. The equation is spot on and corresponded with the graph of the current through the resistor at different times.
Coz current choose low resistive path to flow, it doesn't flow through 20k ohm resistor and since current is zero, we are assuming there is no 20k ohm there
20 kΩ resistor is in parallel to the capacitor. When the capacitor acts as a short circuit then 20 kΩ resistor will be in parallel to a short circit. So, it will also get short circuited. I hope it will clear your doubt.
At t= 0-, the entire 2.5 A current is flowing through inductor as it will act as a short circuit. At t= 0+, when the switch is opened, the inductor acts as a current source of 2.5 A and it supplies current to the resistor which is connected in parallel to it. While the current of 2.5 A (form independent current source on the left) will flow through another 20 ohm resistor at t= 0+. I hope, it will clear your doubt.
In last example we have not to find current through inductor.We have to find current through 10 ohm resistor.. So why we used the Inductor Current formula I(L)at t.
That formula is also vaild for finding the current through the resistor. Because we are taking the current through the resistor at t=0 and t = ∞in that equation. Alternatively, if you are still in doubt, you can find the current through the inductor using the same formula and then applying at the KCL at the common node, you can find the current through 10 ohm resistor. 1.5A = IL(t) +2*Ir(t) You will get the same result. I hope it will clear your doubt.
At t=0+, the capacitor will act as a short circuit. Since, the 20k resistor is in parallel with capacitor, so it will also get short circuited. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS Thank you for the explanation! But is it a general rule? As in if something is shorted in a branch, everything in the branch opposite to the first branch will also be shorted?
5:52 sir the capcitor is shortckted due to its property but why is the 20kohm shrtckted sir why cannot the loop b closed so that it forms a new circuit with 2 20kohm resistors
If you look at the circuit at t= infinity at 7:18, then at t= infinity, the capacitor will act as open circuit and hence no current if flowing through capacitor. Therefore, Ic (infinity) = 0. I hope, it will clear your doubt.
At t= 0-, the switch is still open. The inductor will act as a short circuit and therefore, only two 10 ohm resistors are there in the circuit. So, current will get equally get divided between two resistors at t= 0-. I hope it will clear your doubt.
at t=0+ inductor acts as open circuit only if current through it was zero earlier. If there was already some current flowing through inductor, it will maintain a same current initially.
The circuit which is shown at 9:50 is for t=0-, where the switch is not opened yet. That means the circuit is in steady state condition. And therefore, inductor will act as a short circuit. I hope, it will clear your doubt.
At t=0-, before the switch is getting closed, the 1.5A current is getting divided between the two 10 ohm resistors. (Considering inductor as short circuit). That's why current through inductor at t=0- would be 1.5/2 = 0.75 A. I hope it will clear your doubt.
In question 3 it is given that switch is opened for a long time then it is closed at t=0 so as switch is open and due to rule ki instant change oppose kerta hai then how current is being flow and and at t=0- how inductor act as short circuit????
Sir in example 2 at t (0+ ) why is the entire current assumed to be going towards the 20 ohm resistor in parallel with the inductor ? Why can't a part of the current go towards the other 20 ohm resistor ?
If you observe, at t= 0+, there are two closed loops. Each with 2.5A current source with 20-ohm resistor. So, at t=0+, the current flowing through each 20-ohm resistor will be 2.5A. But in the example, as we have been asked to find the voltage across the bottom 20-ohm resistor, I didn't mention about the second resistor. I hope it will clear your doubt.
@@ALLABOUTELECTRONICS why there is current in bottom 20 ohm resistance if should not, all current is through short circuit... Then voltage across bottom 20 ohm resistance should be 0 sir
Resistor is in parallel to capacitor. Since, capacitor acts as a short circuit, the resistor will also get short circuited. I hope it will clear your doubt.
Hi there was a superb video and it is easy to learn. My humble request is plz make video about intial condition this is chapter of Circuits and network. (BE EC 3rd Sem)
When the capacitor acts as a short circuit then it offers zero resistance. And anything which is in parallel to it will also get short-circuited (Req = R1*R2 / (R1+R2), if R1 or R2 is zero, then the equivalent resistance Req = 0). Because the entire current flows through the capacitor. I hope it will clear your doubt.
Very good explanation..please do more videos on second order series & sinusoidal ,step ,square response as well as the parallel rlc ckts , concept s damping factor ,root locus
At time t= 0+, the capacitor will act as a short circuit. And the resistor is in parallel with this capacitor. Ao, it will also act as a short circuit.
in 2nd question voltage across 20 ohm should be Ldi/dt but since at t=0+ di/dt is 0 voltage across 20 ohm should also be zero ? please clarify it If mine explantion is wrong explain it how?
You also need to consider the initial condition. At t= 0-, the current is already following through the inductor. You also need to take this into consideration. What you are saying is true, if no current is flowing through the inductor at t = 0 -.
It is not inductor current. Its capacitor current only. The formula I (t) = i (∞) + [ i (0) - Ic (∞)] * e^(-t/T) is the general formula for first-order RC or RL circuits. It can be used for both inductors and capacitors. Only the time constant T will change. For RC circuit T = RC. For RL circuit T = L / R. I hope, it will clear your doubt.
Sir u r telling that two resistance which r parallel are in series with third resistance,then how can u divde voltage equally between 3 resistance (example 3) pls explain me🙏🙏🙏
Before time t=0, when the switch is open, in steady-state, the inductor will act as an open circuit. And hence, 1.5A will get divided between two 10 ohm resistors. (i.e 0.75A)(Another 10-ohm resistor is still open at t=0-). At time t=0+, once the switch is closed, then there will be three 10 ohm resistors in the circuit. But as you are aware, the inductor opposes the instantaneous change in the current. That means current through the inductor at t=0+ will also be 0.75 A. Hence, the current, through a resistor which is in series with inductor will also be 0.75A. The remaining, 1.5 - 0.75 A will get divided between the two resistors. Now, at a steady state, once again, the inductor will act as a short circuit (after t=0+). And in that case, as shown at 13:59, three resistors will be in parallel. So, current will get equally get divided between them. I hope it will clear your doubt.
I(0+) current through the resistor will be, 0.375 A, as 0.75 A current will be divided between two 10 ohm resistors. If you are taking about inductor current at t=0+, it is 0.75 A.
@@ALLABOUTELECTRONICS Shouldnt I use the current in the Inductor (0.75) not the resistor (0.375)? Plus I don't understand how the current in the resistor was 0.375 .. we completely ignored the main current source in this computation
The V/I relationship for resistors is constant, we use Ohms law to determine them. The value of voltage and current also change instantaneously, so there is no need for i(infinite) and i(0).
At t= infinity, the circuit is in steady state. so inductor will act as a short circuit. And the current which was flowing through the inductor will continue to flow through it. So, here there is no need to show it through a separate current source.
Because the current I(t) is the current flowing through the 10-ohm resistor. And to find that we need to consider these resistors. I hope it will clear your doubt. If you still have any doubt then do let me know here.
If you apply KCL at that node, then remaining 0.75 A current should leave the node towards two 10 ohm resistors. Similarly, at the datum node or reference node, the summation of currents through resistors and 0.75A should sum up to 1.5 A. And that is only possible when current is leaving through resistors and not entering into them. I hope it will clear your doubt. And still, if you have any questions then do let me know here.
At t=0-, the switch is in a closed condition, and inductor acts as a short circuit ( considering switch is closed since a long time, that will be a steady state condition for the inductor). Because of that, 20 ohm resistor in parallel to inductor will get short circuit. And overall, there will be a short circuit in parallel to current source. So, 20 ohm resistor, which is connected in parallel to current source will also get short circuited. And therefore, entire 2.5 A current will flow through short circuit. Or in other words, 2.5 A current will flow through the inductor. So, we can say that, at t=0-, inductor current is 2.5 A. I hope, it will clear your doubt.
In 1st question, we can also find capacitor voltage first at t>0 and then we can find ic(t) across capacitor then why answer is differing. Please explain
1.5 A current is getting divided between the two 10 ohm resistors. That means half of 1.5 A (0.75A) will flow through one 10 ohm resistor and the remaining 0.75 A will flow through second 10 ohm resistor. That's why its 1.5/2. I hope it will clear your doubt.
@@ALLABOUTELECTRONICS at t=0- as inductor is short circuited then three 10 ohm resistors will be there.then current is 1.5/3.but why 1.5/2 I did not understood please explain
Because the Vx is measured from the right to the left. I mean positive terminal is on the right side, while the negative terminal is on the left side. While the current is flowing in the anti-clockwise direction (from left to the right in resistor). that's why there is a minus sign. I hope it will clear your doubt.
See, the initial current through the inductor is 0.75A. But we have been asked to find the current through the 10-ohm resistor. (The second 10 ohm resistor which is in parallel with another 10 ohm resistor) So, at t=0+, out of 1.5 A, 0.75 A current will flow through the inductor. And remaining 0.75 A current will equally get divided between two 10 ohm resistors. That's why it is 0.375A. I hope it will clear your doubt.
I hope you are talking about the circuit in which current source is connected in parallel with R and C. (i.e parallel RC circuit). Well, in that case, the capacitor voltage equation will remain same, Vc(t)= V([1-e^(-t/RC)] ; where V is the final value or voltage across capacitor in steady state. Please try it by yourself by applying KCL in such circuit.
I am referring to the steady state condition before the switch was opened. In steady state condition, it will act as a short circuit. I hope, it will clear your doubt.
Although the switch is open at t=0-, the current will still flow through inductor via a 10-ohm resistor. If you closely look the circuit, the 1.5A current will through 10-ohm resistor and, 10hm resistor and inductor pair. I hope it will clear your doubt.
If you observe, the switch is connected to the resistor (and not to inductor). So before t=0, in steady state condition, it will act as a short circuit. (i,e at t=0-). And when the switch is closed, it will act as a current source. I hope it will clear your doubt. If you still have any doubt then do let me know here.
SIR in qno 3 ,the question was like the circuit has been open for a long time and that at t=0 the switch is closed. that means at t=(0-) inductor should have been an open circuit becoz the current flowing is zero n in t=0+ also inductor should act as open circuit.why u have shown it as closed circuit as the circuit has closed just then ?
The property of inductor is that it opposes the instantaneous change of current. It means that if any current is flowing through inductor at t=0-, then same current will flow at t=0+ too. Here in example 3, at t=0-, the current through the inductor is 0.75A. So, the same current will continue to flow through inductor at t=0+ as well. I hope it will clear your dobut.
Here I(o) is the current through 10-ohm resistor which is in parallel. I think you misunderstood the resistor which is in series with an inductor. Please check it once again. And still, if you have any confusion then do let me know here.
@@ALLABOUTELECTRONICS sir at 11.53 but in the question u don't mention its charged for some time how to take it as a short ckt ( can I take it as charging from initial(0A))
sir for practicing more problems not only for this topic for imp.topics post some WORKSHEETS in the description with solns it will b more hlp ful for students like me
There is a seperate channel for the questions. Please check ALL ABOUT ELECTRONICS- QUIZ. You will find the different playlist. ( You may check Network Analysis playlist)
In the first example, the voltage across the capacitor is zero at time t= 0-. And capacitor opposes the instantaneous change in the voltage. That means Vc(0+) = 0V. Hence, at t= 0+, the capacitor can be replaced by the short circuit. And as 20k ohm is in parallel with the capacitor, it will also get short-circuited at time t= 0+. I hope it will clear your doubt.
Sir can you please provide the solved examples with all minor details in the form of pdf that you have solved for practice & please refer textbook for us.... Our exams are round the corner please help sir
Yes, I will upload the pdf of solved examples in 2-3 days. And you can refer books like Network analysis by Van Valkenburg (But initially it will be slightly difficult to understand) Or you can refer Network analysis and synthesis by S.P Ghosh and A K Chakraborty
only one doubt. we have to find Req for Time constant at which time. in first example it was found at time t=0 and in third it was found at time t=0+ , can anyone plz help ?
so why was it found for t=0 in example 1 ? this one doubt is scrambling my mind otherwise got all my concepts clear about transient. can you help me clear this one ?
In example 1 also, RC time constant is in fact at time t>0 only. In example 1 circuit is same (Circuit components are same) at time t=0- and t=0+. In some cases, particularly when you have the switch in the circuit which connects some part of the circuit with another part at time t=0, there you will see the difference in time constant at time t=0- and time t=0+. I hope, now it will clear your doubt. If you still have any confusion, then do let me know here.
See, the capacitor will act as a short circuit at time t=0+, or Vc(0+)=0, that is initial condition of the circuit. But it doesn't mean capacitor is not present in the circuit at time t=0+ and so as the resistor. So, physically both are present in the circuit and so they are in finding the time constant of the circuit. While, if you see in some examples where the switch is connecting any element or some part of the circuit to the another circuit. In that case at t=0+ and t=0-, the circuit will be different physically. (might have additional components depending upon the switch position). In such case time constant of the circuit will be different at time t=0+ and t=0-. So, in that sense in example 1, the circuit will be same at time t=0+ and t=0-. I hope it will clear your confusion.
If you closely look at the question, it has been asked to find the current through a 10-ohm resistor at time t= 0+. Of course, the current through the inductor will be 0.75A. But that current will equally get divided between two 10 ohm resistors at time t=0+. That's why it is 0.375A.
The solution of the examples given for the practice has been uploaded in the PDF format.
drive.google.com/file/d/0B3FOmN0FcD6OWFc2OXAtcUtmcXc/view?usp=sharing&resourcekey=0-yNuVb1wrtYbtPSk9wSTHuA
ALL ABOUT ELECTRONICS
Sir plz send me more examples. Very important sir
🙂😇
How could I ever thank you for saving my life with these short and informative videos
wow!!! while going over this in class and reading the textbook, this topic was clear as mud. I watched this and saw how you explained these circuit analysis and I have a greater clarity on what is going on. Keep up the great work on your videos because they help a lot.
16:22 sir il at 0- and 0+ are equal to 0.75 then y have u writtten at 0 0.375 flows it flows through the parallel resistors isn't sir
I think so too
Excellent work again. I did confirm example 3 using LTspice. The equation is spot on and corresponded with the graph of the current through the resistor at different times.
at 5:40, i didn't quite get how capacitor get shorted in the equation. Can you elaborate it more?
Coz current choose low resistive path to flow, it doesn't flow through 20k ohm resistor and since current is zero, we are assuming there is no 20k ohm there
thank you for these clear videos. they have helped me in my circuits class so much!
Sir we have to find i(t) which is the circuit response or current through inductor so why we are using 0.375 instead 0.75
We use .75 amp at t=0+ not .375
We are asked to find the current of one of the resistors, not of the inductor. be careful
Yes we have to use i0+=0.75 in this formula that is current through inductor.
I don't understand how(in 6:05) the capacitor becomes short circuit(which is fine) but then how did the 20K ohm become short? Can you explain?
20 kΩ resistor is in parallel to the capacitor. When the capacitor acts as a short circuit then 20 kΩ resistor will be in parallel to a short circit. So, it will also get short circuited. I hope it will clear your doubt.
10:49 Example 2 why the 2.5A current didn't divide between inductor and resistance branches?
At t= 0-, the entire 2.5 A current is flowing through inductor as it will act as a short circuit. At t= 0+, when the switch is opened, the inductor acts as a current source of 2.5 A and it supplies current to the resistor which is connected in parallel to it. While the current of 2.5 A (form independent current source on the left) will flow through another 20 ohm resistor at t= 0+. I hope, it will clear your doubt.
In last example we have not to find current through inductor.We have to find current through 10 ohm resistor.. So why we used the Inductor Current formula I(L)at t.
That formula is also vaild for finding the current through the resistor. Because we are taking the current through the resistor at t=0 and t = ∞in that equation.
Alternatively, if you are still in doubt, you can find the current through the inductor using the same formula and then applying at the KCL at the common node, you can find the current through 10 ohm resistor.
1.5A = IL(t) +2*Ir(t)
You will get the same result.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS sir will you make video on that pls
@@sujatasapte5959 I have already covered many similar type of examples on the second channel.
Please go through it.
@5:47 why does the 20kohm get shortcircuited along with the capacitor?
At t=0+, the capacitor will act as a short circuit. Since, the 20k resistor is in parallel with capacitor, so it will also get short circuited. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS Thank you for the explanation! But is it a general rule? As in if something is shorted in a branch, everything in the branch opposite to the first branch will also be shorted?
Yes, in parallel, if any branch is short circuited, then every branch in parallel to it will also get short circuited.
@@ALLABOUTELECTRONICS Thank you so much!
5:52 sir the capcitor is shortckted due to its property but why is the 20kohm shrtckted sir why cannot the loop b closed so that it forms a new circuit with 2 20kohm resistors
Sir please can u explain me why u put Ic(infinity)=0??? At time*8:22*
If you look at the circuit at t= infinity at 7:18, then at t= infinity, the capacitor will act as open circuit and hence no current if flowing through capacitor. Therefore, Ic (infinity) = 0. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS clear sir , thank u
on minute 11:50 how he can get 1.5/2..can you explain about how u can get 2?
At t= 0-, the switch is still open. The inductor will act as a short circuit and therefore, only two 10 ohm resistors are there in the circuit. So, current will get equally get divided between two resistors at t= 0-.
I hope it will clear your doubt.
you said at t=0+
inductor act as open ckt
where it used ????
at t=0+ inductor acts as open circuit only if current through it was zero earlier. If there was already some current flowing through inductor, it will maintain a same current initially.
Hello, with the 1st problem, initial current is 0.5mA, why you just use 0.5 in the i(t) equation you forgot *10^-3.
Noticed the same too it could be an oversight
@@jeffreyaigbovbiosa7880Yeah me too noticed the same.
yeah, I too found the same thing, it is 0.5 milliampere, so have to multiply the same with the output!
Sir at 5:50 why is 20k ohms resistor is short?
Because potential is same in parallel .zeo potential simply represent by wire.
Isn't the inductor going to be open circuit at 9:50
The circuit which is shown at 9:50 is for t=0-, where the switch is not opened yet. That means the circuit is in steady state condition. And therefore, inductor will act as a short circuit. I hope, it will clear your doubt.
At 11:54 from where has that 2 in denominator come from
At t=0-, before the switch is getting closed, the 1.5A current is getting divided between the two 10 ohm resistors. (Considering inductor as short circuit). That's why current through inductor at t=0- would be 1.5/2 = 0.75 A.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS thank you for clearing my doubt
Bro..but as two 10ohm resistors are in parallel Req=5ohms
sir please do video of two port network
In question 3 it is given that switch is opened for a long time then it is closed at t=0 so as switch is open and due to rule ki instant change oppose kerta hai then how current is being flow and and at t=0- how inductor act as short circuit????
Switch to open tha to 0- pe inducors short kaise hoga???
Pls reply
12:07 where is the 2 coming from
Because of symmetry ( same 10 ohm resistor)
in 3rd question while finding time constant why do we take Req at t = 0+ and not at t = infinte? why should inductor be included?
Sir in example 2 at t (0+ ) why is the entire current assumed to be going towards the 20 ohm resistor in parallel with the inductor ?
Why can't a part of the current go towards the other 20 ohm resistor ?
If you observe, at t= 0+, there are two closed loops. Each with 2.5A current source with 20-ohm resistor. So, at t=0+, the current flowing through each 20-ohm resistor will be 2.5A. But in the example, as we have been asked to find the voltage across the bottom 20-ohm resistor, I didn't mention about the second resistor.
I hope it will clear your doubt.
What if the risistors aren't the same resistance. Will they be -V/R?
@@ALLABOUTELECTRONICS sir please be more specific . Unable to understand
@@ALLABOUTELECTRONICS how is it possible why won the 2.5 A current pass through short circuit instead of going through resistance?
@@ALLABOUTELECTRONICS why there is current in bottom 20 ohm resistance if should not, all current is through short circuit... Then voltage across bottom 20 ohm resistance should be 0 sir
hello, sir. in example 2, why is the voltage at the resistor negative?
The current and Voltage are in opp. direction
Sir please give some clarity to the doubts asked by others.... It might help others for getting more clarity information...
At 5:50 why resistor is short circuited
Resistor is in parallel to capacitor. Since, capacitor acts as a short circuit, the resistor will also get short circuited.
I hope it will clear your doubt.
in which particular branch we have to find out i(0-) and i(infinite)
Superb and simple explanation 👌
6:48 WHY CAPACITOR ACT AS OPEN CIRCUIT???
In 2nd example why current you get in negative value (-2.5A) passing through inductor? 🤔
It is not negative. It is +2.5 A only. There is no negative sign.
why I(0+) is taken as the current flowing through the switch but not through the inductor?
Hi, would you please mention the timestamp where you are refering. It would easy for me to answer your question.
@@ALLABOUTELECTRONICSat 13:00
Bruh amazing videos, so clear
Hi there was a superb video and it is easy to learn.
My humble request is plz make video about intial condition this is chapter of Circuits and network.
(BE EC 3rd Sem)
I have already made a video about the initial conditions.
Please check the following video:
ua-cam.com/video/3YinmbkU0DE/v-deo.html
If capacitor is shot circuited then why the parallel register also gets short circuited ??? Please help 🙏🙏🙏 🙏🙏🙏
When the capacitor acts as a short circuit then it offers zero resistance. And anything which is in parallel to it will also get short-circuited (Req = R1*R2 / (R1+R2), if R1 or R2 is zero, then the equivalent resistance Req = 0). Because the entire current flows through the capacitor.
I hope it will clear your doubt.
NOTHING BUT.........................................................AWESOME
At 8:51 E to the power 25t kaise hua...?
1÷40×1,000 = 25 as it is given that 1÷40 and unit is given in ms, so it is 25
Sir why you divide current 1.5 by 2
Very good explanation..please do more videos on second order series & sinusoidal ,step ,square response as well as the parallel rlc ckts , concept s damping factor ,root locus
Sir why you short circuit the resistor at 5:50
Also at 9:53 when u short circuit the inductor u also short the resistor which is in parallel with this inductor.can u explain sir
At time t= 0+, the capacitor will act as a short circuit. And the resistor is in parallel with this capacitor. Ao, it will also act as a short circuit.
in 2nd question voltage across 20 ohm should be Ldi/dt but since at t=0+ di/dt is 0 voltage across 20 ohm should also be zero ?
please clarify it If mine explantion is wrong explain it how?
You also need to consider the initial condition. At t= 0-, the current is already following through the inductor. You also need to take this into consideration. What you are saying is true, if no current is flowing through the inductor at t = 0 -.
sir in example 1 how you used formulla of inductor current as capacitor current
It is not inductor current. Its capacitor current only. The formula I (t) = i (∞) + [ i (0) - Ic (∞)] * e^(-t/T) is the general formula for first-order RC or RL circuits. It can be used for both inductors and capacitors. Only the time constant T will change. For RC circuit T = RC. For RL circuit T = L / R. I hope, it will clear your doubt.
For finding equivalent resistance we have to short circuit the independent sources or open circuit them??
If the independent source is voltage source then it will be short circuited. If it is independent current source then it will be open circuited.
Sir u r telling that two resistance which r parallel are in series with third resistance,then how can u divde voltage equally between 3 resistance (example 3) pls explain me🙏🙏🙏
Before time t=0, when the switch is open, in steady-state, the inductor will act as an open circuit. And hence, 1.5A will get divided between two 10 ohm resistors. (i.e 0.75A)(Another 10-ohm resistor is still open at t=0-).
At time t=0+, once the switch is closed, then there will be three 10 ohm resistors in the circuit. But as you are aware, the inductor opposes the instantaneous change in the current. That means current through the inductor at t=0+ will also be 0.75 A. Hence, the current, through a resistor which is in series with inductor will also be 0.75A.
The remaining, 1.5 - 0.75 A will get divided between the two resistors.
Now, at a steady state, once again, the inductor will act as a short circuit (after t=0+). And in that case, as shown at 13:59, three resistors will be in parallel. So, current will get equally get divided between them.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS thank you sir 🙏🙏🙏
in qs 3 , why you used i 0+ as .375 ? should it be .75 ?
I(0+) current through the resistor will be, 0.375 A, as 0.75 A current will be divided between two 10 ohm resistors. If you are taking about inductor current at t=0+, it is 0.75 A.
@@ALLABOUTELECTRONICS So, that's why we should use 0.75 as initial current in inductor
@@ALLABOUTELECTRONICS Shouldnt I use the current in the Inductor (0.75) not the resistor (0.375)? Plus I don't understand how the current in the resistor was 0.375 .. we completely ignored the main current source in this computation
Great job man ... you did an amazing things👌
sir, can we use this formula 【i(t)=i(inifinite) + ( i(0)-i(infinite))*e^(-t/T)】for resistor also???
The V/I relationship for resistors is constant, we use Ohms law to determine them. The value of voltage and current also change instantaneously, so there is no need for i(infinite) and i(0).
In the third example at t =infinity, why is the inductor considered as short circuit and not as a current source along with the short circuit?
At t= infinity, the circuit is in steady state. so inductor will act as a short circuit. And the current which was flowing through the inductor will continue to flow through it. So, here there is no need to show it through a separate current source.
Sir to find I(t) why are we considering the current through a resistance parellel to the inductor in example 3
Because the current I(t) is the current flowing through the 10-ohm resistor. And to find that we need to consider these resistors. I hope it will clear your doubt. If you still have any doubt then do let me know here.
Sir in the first problem how can u write the current equation I(t) for the capacitor as it is mentioned already that is used for inductor
Are you talking about the first problem solved in the video or the practice problem given in the description?
sir at 12.54 why did you take the 0.75A of current as leaving for the node ..why it can't be incoming?? please answer my question
If you apply KCL at that node, then remaining 0.75 A current should leave the node towards two 10 ohm resistors.
Similarly, at the datum node or reference node, the summation of currents through resistors and 0.75A should sum up to 1.5 A. And that is only possible when current is leaving through resistors and not entering into them.
I hope it will clear your doubt.
And still, if you have any questions then do let me know here.
ALL ABOUT ELECTRONICS Thank you sir..I got my doubt clarified..
At 10:14 how iL(0^-) = 2.5 A
At t=0-, the switch is in a closed condition, and inductor acts as a short circuit ( considering switch is closed since a long time, that will be a steady state condition for the inductor). Because of that, 20 ohm resistor in parallel to inductor will get short circuit. And overall, there will be a short circuit in parallel to current source. So, 20 ohm resistor, which is connected in parallel to current source will also get short circuited. And therefore, entire 2.5 A current will flow through short circuit. Or in other words, 2.5 A current will flow through the inductor. So, we can say that, at t=0-, inductor current is 2.5 A. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS thanks alot sir ❤
please help me. my lecture give me quiz but there is no R. how can i find that resistor :(
In 1st question, we can also find capacitor voltage first at t>0 and then we can find ic(t) across capacitor then why answer is differing. Please explain
We cannot find capacitor voltage at t>0.because.there it is open circuit.
How do i know when i am to find the current at infinity ?
Sir, how about if the current source is being series with RC circuit? what is the proper computation for that? thanks
In that case, the current through the circuit will remain the same. Only the voltage across the capacitor will change with time (as capacitor charges)
sir.in example 3.
At i=0-
I(l)=1.5/2..from where did we get 2. Can you say?
1.5 A current is getting divided between the two 10 ohm resistors. That means half of 1.5 A (0.75A) will flow through one 10 ohm resistor and the remaining 0.75 A will flow through second 10 ohm resistor.
That's why its 1.5/2.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS ss very clear
@@ALLABOUTELECTRONICS at t=0- as inductor is short circuited then three 10 ohm resistors will be there.then current is 1.5/3.but why 1.5/2 I did not understood please explain
Sir excellent explanation ....Thank u....
At 10.47 why it is minus 2.5A ???
Because the Vx is measured from the right to the left. I mean positive terminal is on the right side, while the negative terminal is on the left side.
While the current is flowing in the anti-clockwise direction (from left to the right in resistor).
that's why there is a minus sign.
I hope it will clear your doubt.
ALL ABOUT ELECTRONICS Thank u
in the example 3, i0+ is .75A but in the formula we have write i0+ is .375A plz tell me
See, the initial current through the inductor is 0.75A. But we have been asked to find the current through the 10-ohm resistor. (The second 10 ohm resistor which is in parallel with another 10 ohm resistor)
So, at t=0+, out of 1.5 A, 0.75 A current will flow through the inductor. And remaining 0.75 A current will equally get divided between two 10 ohm resistors.
That's why it is 0.375A.
I hope it will clear your doubt.
In parallel rlc circuit how can we consider case 4: R=0 as R is in denominator of alpha
But you explanation is awesome
Yes, That's by mistake. It should have been R = ∞.
Hlo bro given circuit is with source or without source how can we gues????
If the circuit has any voltage or current source then it means that, some source is connected with the circuit.
sir what is the o/p if we connect current source to rc ckt
I hope you are talking about the circuit in which current source is connected in parallel with R and C. (i.e parallel RC circuit). Well, in that case, the capacitor voltage equation will remain same,
Vc(t)= V([1-e^(-t/RC)] ; where V is the final value or voltage across capacitor in steady state.
Please try it by yourself by applying KCL in such circuit.
Eg. 2 At t=0, shouldn't the Inductor become Open Circuit?
I am referring to the steady state condition before the switch was opened. In steady state condition, it will act as a short circuit.
I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS Yes, it did. Thank you.
thank you so much sir for making such a usefull vedio
sir please give the answer of pdf question for confirmation...only answer
which tablet/phone do uu use ?
What if the capacitor has some initial charge and the switch is closed at t=0
If it has some initial charge, then it will act as a voltage source at t =0 +.
for i(0) ,should we take i(0+) or i(0-) ?
I (0+)
Thankyou sir, you cleared all my doubts!🙏
At 11.53 why inductor shortckt
At t= 0- the switch is opened that means no current flow in that case inductor is oc
Plz clarify my doubt
Although the switch is open at t=0-, the current will still flow through inductor via a 10-ohm resistor. If you closely look the circuit, the 1.5A current will through 10-ohm resistor and, 10hm resistor and inductor pair.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS tq sir
It is a great explanation but , in the third example how can the inductor acts as a short circuit at t=0?
I mean at t=0_,,how it acts as short ckt? wasn't it open long before t=0?
If you observe, the switch is connected to the resistor (and not to inductor). So before t=0, in steady state condition, it will act as a short circuit. (i,e at t=0-). And when the switch is closed, it will act as a current source.
I hope it will clear your doubt. If you still have any doubt then do let me know here.
Exactly, I have gotten it.
Sir in extra example 1
At t=0+ why 8ohm resistor is considered?..
Req and ceq nikalne k liye t =infinity pe nikalenge ya t =0
Just draw the circuit at t=0+. And for that circuit, find the Ceq and Req.
@@ALLABOUTELECTRONICS ok then at 7:00 Req would become 20k as at t=0+ only 20k is in circuit as capacitor is short circuited.
minus 2.5 kese explain toh kro pura
SIR in qno 3 ,the question was like the circuit has been open for a long time and that at t=0 the switch is closed. that means at t=(0-) inductor should have been an open circuit becoz the current flowing is zero n in t=0+ also inductor should act as open circuit.why u have shown it as closed circuit as the circuit has closed just then
?
The property of inductor is that it opposes the instantaneous change of current. It means that if any current is flowing through inductor at t=0-, then same current will flow at t=0+ too. Here in example 3, at t=0-, the current through the inductor is 0.75A. So, the same current will continue to flow through inductor at t=0+ as well.
I hope it will clear your dobut.
thnks alot..
In example 3, if current through inductor at t =0+ is 0.75A as you said then why have you taken i(0) as 0.375A at 16:18 in the final formula?
Here I(o) is the current through 10-ohm resistor which is in parallel. I think you misunderstood the resistor which is in series with an inductor. Please check it once again. And still, if you have any confusion then do let me know here.
@@ALLABOUTELECTRONICS sir at 11.53 but in the question u don't mention its charged for some time how to take it as a short ckt ( can I take it as charging from initial(0A))
There was one doubt if value of the is given then how to find e^( )..
Superb Presentation!!
sir for practicing more problems not only for this topic for imp.topics post some WORKSHEETS in the description with solns it will b more hlp ful for students like me
There is a seperate channel for the questions. Please check ALL ABOUT ELECTRONICS- QUIZ. You will find the different playlist. ( You may check Network Analysis playlist)
@@ALLABOUTELECTRONICS thank you sir ...🤩
20 kohm is short circuited? Can anyone tell?
In the first example, the voltage across the capacitor is zero at time t= 0-. And capacitor opposes the instantaneous change in the voltage. That means Vc(0+) = 0V. Hence, at t= 0+, the capacitor can be replaced by the short circuit. And as 20k ohm is in parallel with the capacitor, it will also get short-circuited at time t= 0+.
I hope it will clear your doubt.
Sir can you please provide the solved examples with all minor details in the form of pdf that you have solved for practice & please refer textbook for us.... Our exams are round the corner please help sir
Yes, I will upload the pdf of solved examples in 2-3 days.
And you can refer books like
Network analysis by Van Valkenburg (But initially it will be slightly difficult to understand)
Or you can refer Network analysis and synthesis by S.P Ghosh and A K Chakraborty
The solution of the examples given for the practice has been uploaded in the PDF format.
drive.google.com/open?id=0B3FOmN0FcD6OWFc2OXAtcUtmcXc
Thank you sir
sir its not opening in google drive sir
Ok, I will check. But it was working till now. Anyway, I will check it once again and if required, will update the link.
Please try now once again. And still if you face any difficulty, let me know.
how to check transients and solve the problem
Draw Req arrow from right to left.
how did you go from 40 to 25?? someone explain please
If you observe 40 is actually 40 ms, that is 0.04 seconds. So, 1/0.04 = 25
I hope it will clear your doubt.
ALL ABOUT ELECTRONICS yes thank you
only one doubt. we have to find Req for Time constant at which time. in first example it was found at time t=0 and in third it was found at time t=0+ , can anyone plz help ?
We always find the time constant of the circuit for time t>0. You can try this for any example on transients.
I hope it will clear your doubt.
so why was it found for t=0 in example 1 ? this one doubt is scrambling my mind otherwise got all my concepts clear about transient. can you help me clear this one ?
In example 1 also, RC time constant is in fact at time t>0 only. In example 1 circuit is same (Circuit components are same) at time t=0- and t=0+. In some cases, particularly when you have the switch in the circuit which connects some part of the circuit with another part at time t=0, there you will see the difference in time constant at time t=0- and time t=0+.
I hope, now it will clear your doubt.
If you still have any confusion, then do let me know here.
I am sorry but I still don't get it. the resistance is short circuited at t=0+ and so is the capacitor. how the circuit is same at t=0- and 0+
See, the capacitor will act as a short circuit at time t=0+, or Vc(0+)=0, that is initial condition of the circuit. But it doesn't mean capacitor is not present in the circuit at time t=0+ and so as the resistor.
So, physically both are present in the circuit and so they are in finding the time constant of the circuit.
While, if you see in some examples where the switch is connecting any element or some part of the circuit to the another circuit. In that case at t=0+ and t=0-, the circuit will be different physically. (might have additional components depending upon the switch position). In such case time constant of the circuit will be different at time t=0+ and t=0-.
So, in that sense in example 1, the circuit will be same at time t=0+ and t=0-.
I hope it will clear your confusion.
SIR
NOW ITS WORKINKG SIR
THANK YOU SIR
Waha t>=0+ bola tha t>=0 nhi. Donome difference nhi hota kya?
How we get 0.75 can u please explain sir
@@preethimj1570 yes explain
@@sumithrasumithra6153 The 1.5 A current divides equally between two 10 ohm branches. So 1.5/2 = 0.75
SIR
BUT FOR SOLUTION IT IS NOT OPENING SIR
IT IS SHOWING THAT GOOGLE DRIVE-ACCESS DENIED SIR
I will check and update that link. I think the old links are not working anymore. Will update them.
@@ALLABOUTELECTRONICSOK SIR
well explanation ️👍❤️
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@8:52 u should say milli ampere as unit
nice explanation brother
amazing explanation!!!
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Sir I want answers for the extra examples
Sir can u make videos on programming of 8051
time (0) in inductor should be open circuit
time (infinity) short circuit
misleading info.
Super ....👌👌👌👌👌👌👌👌
At t=0+ we use .75 amp not .375
If you closely look at the question, it has been asked to find the current through a 10-ohm resistor at time t= 0+. Of course, the current through the inductor will be 0.75A. But that current will equally get divided between two 10 ohm resistors at time t=0+. That's why it is 0.375A.