VOLTAGE DROP AND CABLE RESISTANCE EXAM PRACTICE - PRACTICE QUESTIONS AND FULLY WORKED ANSWERS

In this LearnElectrics video, we take a look at calculating voltage drop in cables and also the resistance of cables in circuits and which formulas to use to calculate the answers. The formulas are not the same for the resistance and voltage drop, they are not same thing, even though they have several symbols in common. Each of the formulas has its own special place in our work, and in the exams and assessments. These types of questions will always come up in electrical exams and in the inspection and test assessments. You need to know how to use them, how to recognise and use the correct formula and which tables should be used with which formula.
We’ve had several questions posted to us where a little confusion has existed over which formula to use and which table to use. Get them the wrong way round and the answers will be wrong.
We are frequently asked … What are the formulas, how do I calculate voltage drop, which tables do I use, and much more.
We will begin with the resistance formula and calculating R1+R2, and which tables to use.
Next, we look at the voltage drop formula and the relevant tables for this.
Then we will show each formula in use with guided questions and answers.
And we will show you how to rearrange the formula and work the calculation backwards.
Each question is fully worked out for you, so that you totally understand how to make the calculations, and we show you where in the tables to find the data that you need.
This is video number 242 and to view all our videos type in LearnElectrics all one word into the UA-cam search bar.
Visit our UA-cam channel where we have many more videos on a wide range of electrical topics.

[@francoistoumany3841]

Thanks Dave for the clarity in your delivery of the subject. I admire your passion and commitment to teach, which truly shines through considering you are going through cancer treatment at the moment. Thanks for your dedication with this, I truly appreciate what you do. Praying your treatment goes well. God bless you 🙏🏽

[@learnelectrics4402]

Thank you, I really appreciate your comments. Yes, cancer treatment is not easy and does slow me down some weeks. The secret is to keep going and do my best. I will beat it. Dave.

[@user-qi8tv2sj4m]

Ace video. What a great refresher for things I forgot and for learning new as well. Thanks mate.

[@azizurrahman6663]

Hi dave excellent video thanks you.
Voltage drop calculation on 3 kw heater you
Put 18×2,5×19 477/1000
Is wrong Voltage drop.
I thing typing mistake
Excellent video thank you so much

[@learnelectrics4402]

Yes, a small typo, should be 12.5 as shown in the previous boxes. The answer is correct though. Dave.

[@chrisheffernan8895]

Great video! I’m a 1st year apprentice who struggles with the science/ maths side of things and your videos are really easy to follow and help me understand all the formulas and calculations. Many thanks and please never stop making videos!

[@learnelectrics4402]

Great to hear that. No intention of stopping, keep learning, its a good trade. Dave.

[@testingtechnicians6751]

As always good one.

[@learnelectrics4402]

Thank you, appreciated.

[@user-sx3cj3jw5w]

thanks very much it is very much educational .

[@learnelectrics4402]

You are welcome and thanks for watching.

[@kevinwhitehouse3998]

Wwell done mate.. great order, logical and clear. I love your tutorials. Thank you.

[@learnelectrics4402]

Glad you like them, lots more to come. Thanks for watching. Dave.

[@docsmi1728]

Much appreciated

[@learnelectrics4402]

Thanks for watching. Lots more to come.

[@norxand]

Excellent as always 😊

[@learnelectrics4402]

Thank you so much, appreciated.

[@Oufg103f]

Great video, shared ❤

[@learnelectrics4402]

Thank you.

[@malachygallagher4936]

Excellent as usual!Regards mg.

[@learnelectrics4402]

Many thanks, appreciated. Dave.

[@Dog-whisperer7494]

Please go back to posting your videos on a Sunday morning . Great video as always

[@learnelectrics4402]

I will try my best. At the moment I'm having a lot of cancer treatment and having to fit my YT time in between hospital visits. But I will get back to normal. Thanks for the support and comments. Dave.

[@proadlekopy]

Dear Dave. I was assuming voltage drop would be the 2.16v X 2 because of live and nuetral

[@learnelectrics4402]

The calculation takes into account the return path, thanks for watching. Dave.

[@unclefedor81]

Hello. Question 6.
Thank you for your videos, they help me a lot in preparing for the 18th Edition exam.
I studied to become an electrician in another country. I noticed that sometimes we have different approaches to searching for the same values.
Please explain why we cannot immediately multiply the resistance of a circuit by the current flowing in it?
Multiply 0.38 by 12.5 and we get a voltage drop in the circuit of 4.75 V
Why make it so complicated - count the length of the circuit, find the voltage drop per amper per meter in the table, and only then calculate the voltage drop in the circuit?

[@danielteyehuago1633]

Please apart from this MFT instrument, which other instrument can be use to determine the resistance value of a cable for for a distance of 1m

[@learnelectrics4402]

I will often use a multi-meter for resistance measurements. Dave

[@danielteyehuago1633]

I'm here again.

[@maxthompson8978]

why did you do kw/230 in question 5 and kw/240 in question 6 ? because the first gives you 13.1 amps and the latter gives you 12.5 amps this giving two different answers both of which options in the answer box. TIA

[@learnelectrics4402]

To get people to read the question. Nothing else. Thanks for watching. Dave.