# Induced EMF in loop in magnetic field

1. Mar 15, 2005

A circular loop of radius 17 cm is located in the plane of the paper inside a homogeneous magnetic field of 0.7 T pointing into the paper. It is connected in series with a resistor of 131 ohm. The magnetic field is now increased at a constant rate by a factor of 2.2 in 15 s. Calculate the magnitude of the induced emf in the loop (in V) during that time.

Ok So first I figured out the area of the loop, and then multiplied this by the B field of .7 T to get the first magnetic flux. I then took the area of the loop, multiplied by (.7+2.2T) to get the second magnetic flux, I then subtracted the first magnetic flux from the second, divided by 15 seconds to get an answer in volts so at least my units are correct, but my answer is wrong!

Area of loop: .090792 m^2
First Magnetic Flux: .063554 Wb
Second Magnetic Flux: .2633 Wb
Voltage=(.2633-.0635)/15 s=.013316 V which is wrong

What am I doing wrong?

2. Mar 15, 2005

### Galileo

Maybe they mean $B_{final}=2.2 B_{initial}$.