Download 3-24-2014 Worksheet - Iowa State University

Electromagnetic Induction
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
German Parada
Phys 222
Dr. Soeren Prell
03/24/2014
Conceptual introduction questions
1) Describe Faraday’s equation in one sentence. Describe Lenz’s Law in one sentence
2) The magnetic flux through a loop can be zero even though there is external magnetic
field. Explain how this can be possible.
3) I have a bar magnet and a flexible copper wire. Describe five ways in which I can
generate a current on the wire with this set-up. Describe three ways in which I will NOT
generate a current on the wire
4) I have a large solenoid (in diameter) with its own power source and an iron ring. Describe
three ways to generate and EMF in the ring and three situations where NO EMF will be
generated. How would the answers change if the ring was wooden?
5) The Earth has a magnetic field parallel to the ground, so when I hold a loop of wire
vertically and spin it, I should get a current. However, I don’t obtain any, why?
Problems
6) A circular loop of wire is located in an area of spatially-uniform
magnetic field pointing toward the page, as shown in the
picture. The magnetic field decreases following the expression
B(t) = 12 exp(-3t)
A – Determine the direction of the current induced in the loop
B – Derive an expression for the induced current as a function
of time
C – Determine ΔVab at times: t=0, t = 1.5, t = 10
7) The One Ring (to rule them all) is dropped between a horseshoe
magnet by a careless Sam Gamgee. Determine whether the current
generated is clockwise or counterclockwise when the Ring is above
the magnet. What about below?
8) A rectangular coil with N loops of wire (length l, height h) is placed at a distance D of a
very long wire carrying current, with the side h parallel to the wire. If the current of the
wire is increasing at a constant rate of dI/dt, determine the direction of the current and the
EMF generated in the coil. Hint: What is the magnetic field created by a wire? What about the
flux across the coil?
9) A uniform magnetic field B pointing in the positive y direction exists in the xz plane in
all points z>0. A square loop of metallic wire of side d is initially located flat (parallel to
the xz plane) with its front edge at z = -2d. The loop moves at a constant velocity v up to
a location z= 2d.
A – Draw a sketch of the problem
B – Indicate when there will be an induced current, and its direction.
C – Determine the force as a function of time required to pull it.
Supplemental Instruction
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