This is the 2017 Edexcel Paper 3, so all about different experiments!
We noticed this one and thought it was interesting and we just felt we give it a go
So essentially this has two solenoids and some magnets on springs
And it states that well!
You're gonna displace magnet A so that it oscillates and the North Pole is in and out.
Simple Harmonic Motion: that gives you a clue, doesn't it? As this motion continues,
Magnet B starts to oscillate. The amplitude of oscillation increases over time.
So your first thing is, well, resonance. You know, recognizing resonance
Here is how we set it up! Just got some magnets inside a coil of wire
I start this one oscillating and you can see over there that one starts oscillating as well
So it's an example of resonance
But it's also a good demonstration of Faraday and Lenz's law!
So when this one is moving up and down inside the coil of wire, you've got a changing flux linkage. So that's here and
d N Ф (change in flux linkage)
So that's your NdФ in Faraday's law! and because you've got a change of flux linkage here,
You have an alternating current over here, and while currents have magnetic fields around them by the right hand grip rule and that
F=Bil So currents have magnetic fields around them so that caused a force on this magnet over here
So what we were expecting (Yeah, I think you can just about see it) is for them to oscillate pi (π radians)  out of phase
So in other words, every half oscillation of this one, this one is going the opposite direction
And that direction is opposite because of Lenz's law which suggests that minus in Faraday and Lenz's law
So this one's going down, this one's going up. And when this one's going up this one's going down. That's basically the explanation
Let's just have a quick look at what they said in the Mark Scheme
Yeah, we pretty much covered everything. As magnet A moves, its coil experiences a change of magnetic flux.
This change in magnetic flux induces an EMF in the coil
The induced EMF causes a current in both coils. The current in the second core
causes a force to act on magnet B.
Driving magnet B into oscillation. Because both mass-spring systems are at the same frequency, resonance occurs.
It really is almost like two separate three mark questions rather than one big six mark question.
 
I always think one of the most important things, the most important skills, for these longer written questions is being able to deconstruct the question and
identify the different parts of it. So really if this was just a question on Faraday's law and a question on resonance-
-you would have found it really easy-
you just recognize the area and just give the same explanation that you'd always give for Faraday's law and the same explanation -
-you'd always give for resonance. So learn those set-explanations and then just identify what set-explanation needs to go into this context!
