Download AP Physics – Worksheet #7: Chapter 22 Magnetic

Name _______________________ Box # ____________ Score ____
AP Physics – Worksheet #7: Chapter 22
Magnetic Induction
Date _____________
Purpose: To understand Magnetic flux, and the electromotive force (emf) due to magnetic
induction.
Faraday’s Law of Induction
−  B
Emf on a wire segment: =vBl
Emf on a wire loop: =
t
Magnetic flux:  B =BAcos 
Lens’ Law:
Emf on a coil:
=−N
 B
t
The direction of the induced emf always opposes the change in flux.
1.
A wire segment with length ℓ = 50 cm is moving to the right at v = 2.5 m/s through a
uniform magnetic field (directed into the page) of 0.3 T. What is the value of the induced
emf (magnitude and direction) on this wire segment?
2.
Consider that the moving wire segment of problem #1 is sliding (without friction) on
metallic rails, creating a circuit. Given the fact
that the rate of change of the area (ΔA/Δt) equals
the length times velocity of the wire (ℓ v = ℓ
Δx/Δt = ΔA/Δt), calculate the induced emf
(magnitude and direction) on the wire using
Faraday’s Law of Induction.
3.
If the resistance of the circuit is 2 Ω, what is the current flowing through the circuit? Which
direction does it flow?
4.
A coil of 20 turns lies in a horizontal plane. Each coil has an area of .04 m2. A magnetic
field of .3 T directed vertically upward exists in the region of the coil. What is the value of
the magnetic flux through the coil?
5.
The coil in question #4 is now rotated so that the plane of the coil is in a vertical plane while
the magnetic field remains directed upward. Now what is the flux through the coil?
6.
If it takes 0.1 s for the coil to be rotated from the horizontal position (problem #4) to the
vertical position (problem #5), what is the average induced emf in the coil during that time?
7.
A bar magnet that is 20 cm long is allowed to drop through a
horizontal loop as shown. The magnet is oriented vertically
with its north pole below its south pole. Use Lenz’s law to
determine the direction of the current that flows in the resistor
connected across the ends of the loop. Let current flowing
eastward be positive. Explain briefly how you determined the
direction of current flow in the resistor in the three cases:
a. When the north pole is approaching the coil from above.
b. When the magnet is in the middle of the coil.
c. When the south pole is below the coil and receding.
8.
The two loops shown to the right lie in a horizontal plane with loop
A just above loop B. For each of the following situations use Lenz’s law
to indicate the direction of current flow in the resistor in loop A. Explain
briefly how you determined the direction of current flow in the
resistor in the two cases:
a. The instant after the switch in loop B is closed.
b. The instant after the switch in loop B is opened