Magnetic Pendulums

Oscillations in the right pendulum triggers oscillations in the left one.
Pendulums oscillate in phase or out of phase, based on the nature of the magnetic field.
Let's explore the basic setup first
This plastic spool is wound with 36 gauge coated copper wire. Almost 3000 turns.
Around 1 meter of wire is kept loose from both ends
This will help in connecting the coil to a multimeter, LED or other coil.
With the help of pencil and spoke we can hang it like this.
Insulation is removed from both ends. Let us connect both ends to LED.
These 4 strong neodymium magnets are attached to the bottle stand with a long screw. The North Pole is marked with Red dot.
With this arrangement, a plastic spool can oscillate freely with a magnet in the center.
When the pendulum oscillates, the LED glows.
Lets position it like this so that we can watch it closely.
As a result of an oscillating coil, current is induced, as it approaches and leaves the strong magnetic field.
LED glows when the coil moves towards the right . Current is induced whenever there is a change in magnetic field. In this case it happens two times. +
If we switch the polarity of the magnetic field , the LED glows when the coil moves towards the left.
Keeping the magnets right in the middle of the coil ensures that change in magnetic field is strong enough to glow the LED in both directions.
Will it oscillate the same way when I connect these two ends ?
Let us try.
After a couple of oscillations, the pendulum stops.
What could be the reason for this ? Changing magnetic field induces current in the coil. Turning it into an electromagnet.
Based on the polarity, magnetic fields interact and the pendulum stops.
We can explore the interaction of these forces by changing the strength of the magnetic field.
Coil oscillates for a longer duration with only a couple of magnets.
Now, let us bring in another such pendulum.
We will connect open ends of both pendulums so that coils are connected. The wires now form a continuous loop.
When the coil on the right oscillates, current induced in it also flows through the coil on the left.
It acts like an electromagnet and interacts with the magnetic field nearby.
As a result it also starts oscillating.
Right now, two coils are oscillating in phase.
We can change the direction of the magnetic field by switching magnets.
This time coils are oscillating out of phase.
Analysis
Let us work with a single coil to know more.
We will replace the LED with a multimeter.
EMF induced in the coil changes as it oscillates with time.
It also changes direction as can be seen with changing sign on the multimeter.
Expected reading for this setup was more than 1.5 V but it looks like the multimeter is not able to record the spike in the short span.
How about the amount of current induced ?
Amount of current induced decreases as oscillations slow down.
Let us bring in an external power supply in the form of two pencil cells.
When current is momentarily passed through the coil, it becomes an electromagnet.
Direction of current flowing through the coil is anti-clockwise.
Similar poles repel, hence it moves to the right
We can change the direction of the magnetic field. With the same direction of current, the coil should move towards the left as opposite poles attract.
Variations
You can try changing the strength of the magnetic field by changing the number or type of magnets on either side. Change the number of turns keeping the strength of the magnetic field the same. Try with different shapes of the coil as well as the magnets. Switching the connections between two coils also changes the oscillation pattern.
Do try this at home.
Thank You

[@raj-m]

SHM + Electromagnetism in a single demonstration. Wow👍👍👍👍👍

[@RavindraGodbole]

Thanks

[@selahattinylmaz45]

It's a nice and informative video, thank you bro👏👏👏

[@Rex2464]

Best example of resonance

[@RavindraGodbole]

Thanks

[@peterk.4266]

Beautiful project sir. Thank you for uploading it for us to see.

[@jiwankumarpandey2409]

Very neat presentation and explanation. 👌

[@ankishtirpude3413]

Nice sir 👍

[@55Ramius]

This is food for thought. Makes me think of variations that might be done. My 12x24 foot building was delivered yesterday and now comes the slow process of getting it set up for lab use. Power, insulation, etc. I am guessing it will be Fall before I can do much of anything. Takes money to speed this process up. : )

[@RavindraGodbole]

All the best. Eager to know variations you are planning for this !

[@55Ramius]

@@RavindraGodbole Not sure right off. One thing came to mind. I forget what they call those 5 balls that you swing one into the other four and it pops the other end ball up. Maybe 5 coils and one long magnet ... Maybe flawed from the start but was just a thought at the time. : )

[@RavindraGodbole]

@@55Ramius Newton's cradle. 😀