An electromagnet consists of an insulated copper wire wound around an iron core and connected to a source of electricity. The magnetism of electromagnets disappears when the electricity is turned off. A student performs two experiments to study the factors that affect the magnetism produced by an electromagnet.
Experiment 1
He prepares an electromagnet by wrapping ten coils of a wire around an iron nail. The wire is then connected to a 4.5-volt battery. Next, the electromagnet is placed close to evenly spread iron paper clips.
He records the number of paper clips that are attracted to the magnet in a table, repeating the activity with different numbers of coils around the nail.
Number of coils Number of paper clips attracted to the magnet
10 6
15 11
20 17
25 23
Experiment 2
In his second experiment, he repeats the same procedure he used in Experiment 1, except that this time he keeps the number of coils the same but changes the battery voltage. He records the number of paper clips attracted each time in a second table.
Battery Voltage (V) Number of paper clips attracted to the magnet
3.0 3
4.5 6
6.0 9
7.5 13
Which question can be answered based on the results of Experiment 2?
A.
How does the strength of an electromagnet vary when the voltage of the power source changes?
B.
How does the strength of an electromagnet vary when the number of paper clips changes?
C.
How does the voltage of an electromagnet vary when the strength of the paper clips changes?
D.
How does the voltage of an electromagnet vary when the number of coils of wire changes?
A. How does the strength of an electromagnet vary when the voltage of the power source changes?
A student wishes to make the magnetic force exerted by the electromagnet shown below greater.
Which procedure step could the student follow to accomplish this goal?
A.
increase the length of wire at location 1
B.
open the switch at location 2
C.
add more batteries in series at location 3
D.
reduce the number of wire turns at location 4
C. Add more batteries in series at location 3
A student places a drop of purple food coloring into one beaker of water at 20°C and another drop into another beaker of water at 50°C. The temperature of the food coloring is 19°C. The picture shows what he observes.
What explains what the student observes in this investigation? Select all that apply.
A.
The food coloring moves faster in hot water.
B.
The food coloring moves slower in hot water.
C.
The food coloring is denser than the cold water.
D.
The food coloring is less dense than the cold water.
E.
The food coloring separates into two different colors.
F.
The food coloring increases the temperature of the water.
A. The food coloring moves faster in hot water.
C. The food coloring is denser than the cold water.
A ball rolls down a grassy hill and eventually comes to a stop. Select three of the reasons the ball comes to a stop.
A.
Friction and drag oppose the motion of the ball.
B.
There is no force acting to move the ball forward.
C.
The force of friction against the ball is decreased.
D.
The forces opposing the ball are unbalanced.
E.
The force of gravity has increased and stopped the ball.
F.
There was too much inertia to keep the ball rolling.
A. Friction and drag oppose the motion of the ball.
B. There is no force acting to move the ball forward.
D. The forces opposing the ball are unbalanced.
A student built a simple electromagnet with copper wire, an iron bolt, and a 1.5-volt battery. The electromagnet was able to lift a paper clip from 3 centimeters away. Select THREE ways the student can increase the strength of his electromagnet.
A.
He can use a thicker piece of copper wire.
B.
He can reverse the orientation of the battery.
C.
He can replace the iron bolt with a wooden rod.
D.
He can add a switch between the battery and the iron bolt.
E.
He can replace the 1.5-volt battery with a battery of higher voltage.
F.
He can use a longer piece of wire that wraps more times around the bolt.
A. He can use a thicker piece of copper wire.
E. He can replace the 1.5-volt battery with a battery of higher voltage.
F. He can use a longer piece of wire that wraps more times around the bolt.
A bowling ball is moving down a flat bowling lane at a constant speed. Which statements best describe the movement of this bowling ball? Select all that apply.
A.
Its movement is caused by unbalanced forces.
B.
Its movement changes without a force acting upon it.
C.
Its movement shows Newton's first law of motion.
D.
Its movement shows Newton's third law of motion.
E.
Its movement shows Newton's second law of motion.
F.
Its movement remains the same unless a force acts upon it.