Download Unit 9: Magnetism and Induction Review KEY

9.
Draw the magnetic field around the wire below. Use the right-hand rule
to determine if it is clockwise or counterclockwise.

10.
What is a solenoid? Why are solenoids better than straight wires for electromagnets?

11.
A transformer changes the voltage of electricity using two coils of wire on
opposite sides of an iron core.
How can a transformer step up voltage? Step down voltage?

20.
A generator converts mechanical energy to electrical energy by spinning a coil in
a magnetic field. It works in the opposite way of an electric motor and produces,
rather than using electricity.
What is the purpose of a transformer? Briefly describe the components.

19.
The current generated in a coil is proportional to the rate of change of the
magnetic field through it. It means that faster moving or stronger magnets
induce more current.
How does a generator work? Compare and contrast it with an electric motor.

18.
Induction is the flow of current due to a changing magnetic field. The magnet
must move near a coil to induce current.
What is Faraday’s Law of Induction? Explain what it means.

17.
The motor will spin counterclockwise because the magnet will
repel the north and attract the south beneath it.
What is induction? What is required for current to be induced in a wire?

16.
A motor spins because magnets are attracted and repelled. By switching poles on
the electromagnet, you can keep up the pattern of attraction/repulsion.
Which way will this motor spin? Explain.

15.
Rotor – rotating portion of motor. Alternating magnets – provide
attraction/repulsion that turns rotor, Commutator – alternates current.
Explain how an electric motor spins. How do you keep it spinning?

14.
The wires will attract because the current flows in the same direction.
What are the three parts of an electric motor? What does each part do?

13.
A solenoid is a coil of wire. Solenoids use less current for a strong
magnetic field than a straight wire.
Will the wires to the right attract or repel? Why?

12.
The current flows counterclockwise.
To step voltage up, the secondary coil has to have more turns than the primary
coil. To step voltage down, the secondary coil has to have less turns.
In a transformer, the input coil has 60 turns while the output coil has 110 turns. Assuming
the input voltage is 120 volts, what is the output voltage?
V1 N1
V1 N2 (120 V)(110 turns)
=
; V2 =
=
= 220 V
V2 N2
N1
60 turns