Question

Unit 5 & 6: Non-Contact Forces Test
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Question
Directions: Read the passage about the factors that affect the magnetism of electromagnets.

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 clip

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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


Another student made an electromagnet with an iron nail with eight coils of wire wound around it connected to a 2-V battery. She wants to increase the strength of the electromagnet. What changes can she make to her design to increase its strength? Select all that apply.

Responses

wrap more coils of wire around the nail
wrap more coils of wire around the nail

use a shorter wire
use a shorter wire

reduce the coils of wire from eight to six
reduce the coils of wire from eight to six

use two 1-V batteries instead of a 2-V battery
use two 1-V batteries instead of a 2-V battery

use a 4-V battery

Answer 1

Correct choices:
- wrap more coils of wire around the nail
- use a 4-V battery

Why:
- More coils produce a stronger magnetic field (Experiment 1 shows strength increases as coils increase).
- A higher voltage supplies more current and strengthens the electromagnet (Experiment 2 shows strength increases with voltage).

Why the others are not good:
- Reducing coils from eight to six would weaken the magnet.
- Two 1‑V batteries in series equal 2 V, so that does not increase strength compared with a single 2‑V battery.
- "Use a shorter wire" is not a clear way to increase strength in this setup and could reduce the number of turns; the safe, tested ways are increasing coils or increasing voltage.