Great question - yes, we know from Lenz's law that the direction of the induced emf will try to oppose the change that caused it. Here, the left end of the coil will behave like a magnetic North to magnetically repel the incoming bar magnet. A magnetic North implies the current will flow aNti-clockwise in the coil, when viewed from the left. We'll be discussing this further in a follow up video.
Can we think of the change in magnetic flux lines as a relative phenomenon? As we ride a bicycle the air particles hit us even though technically we are hitting them. The effect is still the same. Whether the loop of wire or the magnet moves the effect from the perspective of the charges in the wire would be the same
Great point - yes. Electromagnetism obeys the principle of relativity, but I've avoided giving explanations based on this since this is beyond A-level.
You are correct that it isn't uniform. At 3:27, I mention that I assume a uniform field to keep things simple. Because of this, the change in flux linkage is NBA. So strictly speaking, NBA/(delta t) doesn't give you the induced emf for a bar magnet being pushed into a coil, but it captures enough of the essential physics to be useful to us in understanding the factors that affect the induced emf.
Thank you for explaining the relation to the area on the coil to the emf intensity. I have been confused by this one all morning!
My pleasure, glad you found it useful :)
Is there a way of finding the direction of the current (in the scenario near the end of the video)? How do you know it is anticlockwise?
Great question - yes, we know from Lenz's law that the direction of the induced emf will try to oppose the change that caused it. Here, the left end of the coil will behave like a magnetic North to magnetically repel the incoming bar magnet. A magnetic North implies the current will flow aNti-clockwise in the coil, when viewed from the left. We'll be discussing this further in a follow up video.
Can we think of the change in magnetic flux lines as a relative phenomenon? As we ride a bicycle the air particles hit us even though technically we are hitting them. The effect is still the same. Whether the loop of wire or the magnet moves the effect from the perspective of the charges in the wire would be the same
Great point - yes. Electromagnetism obeys the principle of relativity, but I've avoided giving explanations based on this since this is beyond A-level.
Isn't the magnet's field not uniform? Doesn't that mean the equations for the change in magnetic flux linkage do not work?
You are correct that it isn't uniform. At 3:27, I mention that I assume a uniform field to keep things simple. Because of this, the change in flux linkage is NBA. So strictly speaking, NBA/(delta t) doesn't give you the induced emf for a bar magnet being pushed into a coil, but it captures enough of the essential physics to be useful to us in understanding the factors that affect the induced emf.