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Electromagnetism — Unit test Answers

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1
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A circuit has a current of 1.2 A. If the voltage decreases to one-third of its original amount while the resistance remains constant, what will be the resulting current?

A
0.3 A
B
0.4 A
C
1.2 A
D
3.6 A
2
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Masako measures a circuit at 12 V and 2 A. Using Ohm's law, what can he calculate for the circuit?

A
resistance ()
Option A
B
resistance (O)
C
current (I)
D
current ()
Option D
3

A circuit has a current of 2 A. If the resistance in the circuit decreases to one-fourth of its original amount while the voltage remains constant, what will be the resulting current?

A
0.5 A
B
2 A
C
4 A
D
8 A
4

According to Ohm’s law, which combination of units is the same as the unit for voltage?

A
ohm ÷ ampere
B
ampere × ohm
C
ohm + ampere
D
ampere ÷ ohm
5

Liang is working with an electrical circuit. She replaces a straight electrical wire with a coiled wire.

A
increase the strength of the magnetic field when current flows through the circuit
B
decrease the strength of the magnetic field when current flows through the circuit
C
increase the current that flows through the wire when the circuit is active
D
decrease the current that flows through the wire when the circuit is active
6

What does voltage describe?

A
how fast current can flow
B
how much current can flow
C
how much a material resists electrical flow
D
how fast a material conducts electrical flow
7

Look at the circuit diagram.

Question illustration
A
one
B
two
C
three
D
four
8

Horatio drew a diagram to illustrate how magnetism is produced by electric currents.

Question illustration
A
Magnetism is not produced by electric currents unless the wire is coiled.
B
The magnetic field does not continually spread outward from the wire.
C
The magnetic field is produced inside the wire, not outside of it.
D
Magnetism is only produced when a metal bar is placed near the wire.
9

A positively charged object is placed to the left of a negatively charged object. Which best describes how the positively charged object will move?

A
to the left, in the direction of the electric field lines
B
to the right, in the direction of the electric field lines
C
up in the direction that the field lines bend away
D
down in the direction that the field lines bend away
10

The north pole of a bar magnet is moved close to the north pole of a second bar magnet. What prediction best describes how the first magnet responds when it is released?

A
It will move toward the second magnet because like poles repel.
B
It will move toward the second magnet because like poles attract.
C
It will move away from the second magnet because like poles repel.
D
It will move away from the second magnet because like poles attract.
11

A component of a circuit changes, as shown below.

Question illustration
A
A switch is closed, so the circuit would be incomplete and broken and the lights in the circuit would not shine.
B
A switch is closed, so the circuit would be complete and unbroken and the lights in the circuit would shine.
C
A switch is opened, so the circuit would be incomplete and broken and the lights in the circuit would not shine.
D
A switch is opened, so the circuit would be complete and unbroken and the lights in the circuit would shine.
12

What must be true in order for magnetism to induce an electric current in a wire?

A
There needs to be a switch in the circuit.
B
There cannot be a switch in the circuit.
C
The wire must be part of a closed circuit.
D
The wire must be part of an open circuit.
13

Parker wound a wire around a large iron nail. He then created an electromagnet by connecting the ends of the wire to different batteries. The table shows the current he measured for each electromagnet.

Question illustration
A
Electromagnet W is the strongest.
B
Electromagnet X is weaker than electromagnet Z.
C
Electromagnet Y is the strongest.
D
Electromagnet Y is weaker than electromagnet X.
14

Two bar magnets are held close together. When they are released, they move toward one another. Which best describes the original placement of the magnets?

A
The magnets are placed end to end with the north pole of each pointing toward the other.
B
The magnets are placed end to end with the south pole of each pointing toward the other.
C
The magnets are placed side by side with the like poles of each magnet near the other.
D
The magnets are placed side by side with the opposite poles of each magnet near the other.
15

Based on illustrations of magnetic field lines, where could an object be placed so it would not experience a magnetic force?

A
halfway between the like poles of two magnets, because the field lines bend away and do not enter this area
B
halfway between the opposite poles of two magnets, because the field lines are the closest together
C
above the middle of a bar magnet, because the magnetic field lines are only found around the sides of the magnet
D
above a pole of a bar magnet, because the magnetic field lines either go in or go out at the end

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