Faraday's Law of Electromagnetic Induction, Magnetic Flux & Induced EMF - Physics & Electromagnetism

The video introduces Faraday's law by demonstrating that a steady current in one coil does not induce current in a second coil, but a changing current does. This change in magnetic field, leading to a change in magnetic flux, is the basis of electromagnetic induction.

Faraday's law states that induced EMF is equal to negative n (number of turns) times the change in magnetic flux divided by the change in time. Magnetic flux is defined as magnetic field (B) times area (A) times cosine of the angle (θ) between the normal line of the coil and the magnetic field.

One way to induce an EMF is by changing the magnetic field, such as moving a magnet into or out of a coil. When the magnet moves, the magnetic field changes, leading to a change in flux and thus an induced EMF and current. If the magnet is stationary, no induced current flows.

A second method to induce EMF is by changing the area of the coil within a constant magnetic field. If the area of the coil increases or decreases, the magnetic flux changes, which induces an EMF and current in the circuit.

The third way to induce EMF is by changing the angle between the magnetic field and the normal line of the coil. Rotating the coil within a magnetic field changes this angle, causing a change in magnetic flux and subsequently inducing an EMF and current.

A practice problem is presented involving a square coil with 50 loops. The magnetic field changes from -3 Tesla to 5 Tesla over 0.1 seconds. The induced EMF is calculated using Faraday's law, followed by the induced current through a 20-ohm resistor, and finally, the power dissipated by the resistor.

The video concludes by highlighting that increasing the number of loops (n) in a coil significantly increases the induced EMF. For example, a single loop would produce a much smaller induced voltage compared to a coil with 50 loops, demonstrating the importance of 'n' in the formula.