Faraday's law simulation

Here is a good visual for Faraday's law of em induction. Remember, it is all about changing magnetic flux! For more PhET physics simulations, go here.

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EM Induction Simulation

Here is a PhET simulation for electromagnetic induction applications. These are great for visualization of what em induction principles look like in the world. For many more physics simulations from PhET, go here.

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How to Find Terminal Velocity of Conducting Loop Falling into B-field

Here is a different type of induction problem. This has to do with the long aluminum tube we have in the lab, and even though it is non-magnetic, a falling magnet in the tube falls with a terminal velocity. Huh?! The reason for this is as the magnet moves, it is changing flux in the loop. This induces a voltage (Faraday) and therefore a current (Ohm). In a tube these are called eddy currents.

But those currents then feel a force since they are in a magnetic field. This is F = Il x B. The force is upward, trying to stop the motion and therefore stopping the change in flux (Lenz). The mathematics turn out to be identical to that of a sky diver with air friction! We will get an exponential solution, and a terminal velocity. Check it out!

How to do Faraday's law for Changing Areas of a Circuit

Here is an example of electromagnetic induction and Faraday's law for a constant B-field and a changing area. A conducting hoop/circuit moves into a B-field, and we determine the induced voltage (i.e. emf) and current. I'll make mention of two different magnetic forces that are relevant here: first, F = qv x B is the force that physically gets the current started since a conductor with free charges is moving through a B-field; second, once that current is turned on, F = Il x B turns on to try and slow the circuit down (magnetic brake). Lenz's law is also discussed.

One other aspect of this is the determination of the velocity of the circuit as a function of time. The magnetic braking force is analyzed with Newton's 2nd law, and we get a similar result as we did in mechanics with air friction, where the force is exponential in time. I hope this helps!

How to Use Faraday's law for cases where B-field Changes

Faraday discovered that any change in magnetic flux causes induced voltage (i.e. electromotive force, or emf) in a closed conducting circuit. Because there is a voltage, this means an electric current is also induced. Faraday's law, or
induced voltage = -d(flux)/dt, allows us to figure out how much voltage is induced. Ohm's law, i = emf/resistance, allows us to figure out how much current turns on, and Lenz's law tells us the direction of the induced current flow.

Lenz's law is "Nature abhors change," or also we could say, "Get the (change in) flux outta here!" All the induced effects fight the change in flux.

Faraday's law helps explain how generators, electric motors, transformers, the ring launcher, credit card scanners, magnetic brakes, and other devices work, so it is tremendously important for everyday life applications. I hope this video helps!