Faraday's and Lenz's laws

Introduction to Induction

Have you ever noticed how your generator works even though there is no battery connected to the wires? It happens because of a special trick in Physics called Electromagnetic Induction. When you move a magnet near a wire, it 'pushes' the electrons inside the wire to start flowing. This is exactly how we get NEPA or PHCN light from big dams like Kainji.

Magnetic Flux Explained

Before we talk about the laws, you must know what Magnetic Flux is. Imagine a net held in front of a fan. The amount of air passing through the net is like the flux. If you tilt the net or move it away, the amount of air changes. In Physics, flux is just the total amount of magnetic field lines passing through a surface.

Simply put, magnetic flux is the total 'amount' of magnetism passing through a loop of wire.

Faraday's Law of Induction

Michael Faraday discovered that as long as the magnetic flux is changing, electricity will flow. If you hold a magnet still inside a coil, nothing happens. But the moment you move it in or out, the galvanometer needle will kick. The faster you move it, the bigger the current.

In simple terms, the faster you change the magnetic field, the more voltage you get.

Lenz's Law

If Faraday tells us 'how much' electricity we get, Lenz tells us the 'direction'. Nature is a bit stubborn; it does not like change. When you try to push a North pole into a coil, the coil turns into a North pole itself to push you back. It opposes your movement.

Basically, the induced current acts like a 'security guard' trying to stop whatever change is happening to the magnetic field.

The Formula for Induction

We combine these laws into one formula: E = -N * (change in flux / time). The minus sign represents Lenz's Law (opposition), and the rest represents Faraday's Law. E is the induced e.m.f. measured in Volts, and N is the number of turns in the wire coil.

Worked Example

A coil has 500 turns. The magnetic flux through it changes from 0.02 Wb to 0.08 Wb in 0.2 seconds. Calculate the induced e.m.f.

1. Identify the change in flux: 0.08 - 0.02 = 0.06 Wb.

2. Use the formula: E = N * (change in flux / time).

3. Substitute the values: E = 500 * (0.06 / 0.2).

4. Calculate: E = 500 * 0.3 = 150 Volts.