Answer to Question #112752 in Electric Circuits for ronnie

Question

Yoon Ki investigates electromagnetic induction by moving a bar magnet into a coil of wire. His experimental setup is shown.

A coil or loop of wire is held horizontally and connected to a galvanometer measuring current. A hand holds a bar magnet and moves it into the coil.

What change would most improve his results?

moving the magnet faster
using more loops of wire in the coil
using the south pole of the magnet
connecting the galvanometer to the coil

Answer 1

The following changes would most improve his results: moving the magnet faster and using more loops of wire in the coil.

1. According to the Faraday's law, EMF in the loop is given by the rate of change of the magnetic flux:

$\mathcal{E} = -\dfrac{\mathrm{d}\Phi_B}{\mathrm{d}t}$ . Moving the magnet faster increases the speed of the magnetic flux changes and, thus, increases the current in the loop.

2. Again, according to the same Faraday's law:

$\mathcal{E} = -N\dfrac{\mathrm{d}\Phi_B}{\mathrm{d}t}$ , where $N$ is number of coil turns. Using more loops of wire in the coil will also increse the EMF and, thus, the current in the wire.