State and use the fact that the effect of the current produced by an induced e.m.f. is to oppose the changeproducing it (Lenz’s law) and describe how this law may be demonstrated

Lenz's Law, named after the German scientist Heinrich Lenz who formulated it in 1834, is a fundamental principle in electromagnetism. It states that the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field.

Here's how you can demonstrate Lenz's Law:

1. Obtain a coil of wire, a strong magnet, and an ammeter (a device used to measure electric current).

2. Connect the coil to the ammeter.

3. Move the magnet towards the coil. As you do this, observe the reading on the ammeter. You will notice that a current is induced in the coil. This is due to Faraday's Law of electromagnetic induction, which states that a changing magnetic field will induce an electric current in a conductor.

4. Now, observe the direction of the induced current. You will notice that the current is in such a direction that its magnetic field opposes the motion of the magnet. This is Lenz's Law in action. If the magnet is moved towards the coil, the induced current will create a magnetic field that tries to push the magnet away. If the magnet is moved away from the coil, the induced current will create a magnetic field that tries to pull the magnet back.

5. To further demonstrate Lenz's Law, you can reverse the direction of the magnet's motion. You will notice that the direction of the induced current also reverses, again creating a magnetic field that opposes the change.

This experiment demonstrates Lenz's Law, showing that the effect of the current produced by an induced e.m.f. is to oppose the change producing it.