# Homework Help: Magnetic Field and induced current

1. Dec 22, 2004

### bchl85

Can anyone help me to do this problem. Thanks in advance.

A closed wire loop in the form of a square of side 4.0cm is mounted with its plane horizontal. The loop has a resistance of 2.0*10^(-3) ohm. The loop is situated in the magnetic field of strength 0.7 T directed vertically downwards.
When the field is switched off, it decreases to 0 at a uniform rate in 0.8s
What is:
a) The current induced in the loop.?
b) The energy dissipated in the loop during the change in the magnetic field?

2. Dec 22, 2004

### Nylex

What have you done so far? You have enough information to work out the EMF induced in the loop, so you can work out the current.

3. Dec 22, 2004

### dextercioby

Here are some formulas that might help:
$$U_{induced}=-\frac{\Delta \Phi_{mag}}{\Delta t}$$
$$\Phi_{mag}=:\vec{B}\cdot \vec{S}$$
$$I_{induced}=\frac{U_{induced}}{R}$$
$$W=U_{induced}I_{induced}t$$

Daniel.

PS.The problem is very easy.Hopefully u'll solve it by yourself...