General Physics II
Recitation Quiz 6 - Electromagnetic Induction
Feb. 24, 2010
For full credit, make your work clear. Show the formulas you use, all the essential steps, and results with
correct units and correct number of significant figures.
1(4). Two loops of wire are moving in the vicinity of a very long straight wire carrying a current as shown in
Figure. Find the direction of the induced current in each loop.
In the loops moving to or from the straight wire the induced current is due to BOTH: the
increase/decrease of the current in the straight wire AND due to the change in the distance
from the straight wire.
2(2). The north pole of the magnet is being inserted into the coil as shown with the arrow. In which direction
is the induced current flowing through a resistor?
From b to a.
3(4). The output voltage of a 95-W transformer is 12 V, and the input current is 22 A.
a) Is this a step-up or step-down transformer?
P = Vin Iin = Vout Iout
Vin = P/Iin = 95W/22A = 4.3V < Vout = 12V
This is a step-up transformer.
b) What is the ratio of secondary to primary turns?
Nout /Nin = Vout /Vin = 12V /4.3V = 2.8