Download EM Induction 1. When a strip of magnetic material, variably

EM Induction
1.
When a strip of magnetic material, variably magnetized, is embedded in a plastic card that is moved past a
small coil of wire, what happens in the coil? Identify one practical application of this (Hint: one such
application is ubiquitous in our capitalist society).
2.
A loop of wired attached to electronic circuitry is embedded in a road surface. The earth’s magnetic field
exists through this loop. A car, whose frame is made of ferromagnetic material, moves over top this
embedded loop toward an intersection. Explain how this setup causes the traffic light to switch from red to
green.
3.
Is it possible to move a conducting loop of wire through a magnetic field without inducing a voltage across the
loop? If so, describe how this could be accomplished. If not, explain why it is impossible.
4.
A vertical spring has a magnet attached to its free end. Pulling the magnet downward and letting it go causes
the system to vibrate in simple harmonic motion. During its oscillation, a closed loop of wire is brought into
the path of the magnet, so that the magnet moves back and forth though the loop. Describe the effect this
has on the motion of the magnet, and explain your answer.
5.
Some bicycles have electric generators that are made to turn when the bike wheel turns. The coil inside this
generator is turned by the spinning front tire and powers a headlamp fastened to the front of the bike. The
cyclist stops pedaling and coasts to a stop. Will the “coasting” distance be affected by the lamp switch being
turned off or on? Explain.
6.
A transformer has 100 turns in its primary coil and 200 turns in its secondary coil.
a. What type of transformer is this?
b. If a voltage of 120 V is placed across the primary, what is the voltage across the secondary?
c. If a current of 4.0 A exists in the primary, what is the maximum current that can flow through the secondary
coil?
7.
A model train requires a low voltage (12 V) to operate.
a. If you wish to plug this train into your wall outlet (120 V), what type of transformer do you need?
b. How many turns must its secondary coil contain?
c. If 1.5 A of current runs through the train, what current is drawn from the wall outlet?