# GCSE Science/Electricity multiple choice

## Question 5

A student rubs a polythene strip with fur and suspends it from a clamp stand. She then rubs another polythene strip with fur and brings it up to the first strip. The two strips repel each other.

Look at the following four statements:

• A) One of the strips is neutral, the other charged.
• B) The strips are both negatively charged.
• C) The strips are both positively charged.
• D) The strips are both neutral.

Which two of the above statements are false?

• A and B

I'm sorry but this is the wrong answer. B is quite possibly true, both rods could be negative because two like charges repel. Hit back and try again.

• A and C

I'm sorry but this is the wrong answer. C is quite possibly true! two positively charged rods would repel each other. Hit back and try again.

• A and D

This is the correct answer. Well done!

• B and C

I'm sorry but this is the wrong answer. If both strops are negative they repel. If ther are both positive they also repel. But the question asked which statements are false. Hit back and try again.

• B and D

I'm sorry but this is the wrong answer. B may very well be true as "like charges repel". Hit back and try again.

• C and D

I'm sorry but this is the wrong answer. C may well be true. Two positively charged strips would repel.

## Question 6

A student decided to silver plate his/her mother's forks. S/he set up the apparatus above. S/he set the power pack and variable resistor so that the ammeter read 0.1 A. S/he allowed the fork to remain in the electrolysis apparatus for 10 min. Once s/he removed the fork s/he tested it by trying to scratch the silver off. S/he found that the layer of silver was too thin and decided that s/he would have to take steps to make the layer a lot thicker.

Which one of the following steps would not produce a thicker layer of silver ?

• Increasing the voltage of the power pack

I'm sorry but this is the wrong answer.

Increasing the voltage would increase the current making the layer of silver thicker. But the question asked which one of the four possible measures would not increase the thickness of the layer.

• Increasing the resistance of the variable resistance

This is the correct answer. Well done!

Increasing the resistance would decrease the current and so decrease the thickness of the silver.

• Increasing the time spent in the apparatus

I'm sorry but this is the wrong answer. Increasing the time gives the silver more time to build up. This means the layer will be thicker.

• Increasing the concentration of the silver nitrate solution

I'm sorry but this is the wrong answer. Increasing the concentration of silver nitrate will mean there are more ions to carry the current. The current will therefore be larger and so the silver layer will be thicker.

The question asked which method would not produce a thicker layer.

## Question 7

What is the maximum power that an appliance should have if it is connect to a 230V supply by a 5A cable ?

• 46W

Sorry this is an incorrect answer. Remember that to find the power you need to multiply the current and the voltage.

• 1.15 kW

Well done this is the correct answer.

• 115W

Sorry but this isn't the correct answer. Be careful about powers of ten when you when you do a calculation, especially when using a calculator.

• 4600W

Sorry this is an incorrect answer. Remember that to find the power you need to multiply the current and the voltage.

## Question 8

The graph above shows how the potential difference across a conductor varied with the current flowing through it. Which of the following statements is true ?

• The resistance of the conductor increases as the current increases

Sorry this is the wrong answer.

From Ohm's Law

R is V/I.

But V/I is also the slope (or gradient) of the line on the graph. So with a constant slope, we must have a constant resistance.

• The resistance of the conductor decreases as the current increases

Sorry this is the wrong answer.

From Ohm's Law

R is V/I

But V/I is also the slope (or gradient) of the line on the graph. So with a constant slope, we must have a constant resistance.

• The resistance of the conductor stays constant as the current increases

Well done this is the correct answer. Recall by Ohm's Law that V is IR and then V/I is R. Observe on the graph that as voltage increases, current increases also. So as these values increase, their quotient must remain relatively constant. So the resistance remains relatively constant.Hence a straight line graph.

• It is not possible to say anything about the resistance of the conductor based on the information given

Sorry this is the wrong answer. It is quite possible to answer this question from the information given.

From Ohm's Law

R is V/I

But V/I is also the slope (or gradient) of the line on the graph. So with a constant slope, we must have a constant resistance.

## Question 9

Two students, Jane and John are working together to make an electromagnet. John coils some plastic coated wire around a pencil and attaches the two ends to a 1.5V cell. He finds the electromagnet that he has made will deflect a compass placed near it but will not pick up a paperclip.

Jane suggest that using an iron nail rather than a pencil will make the magnet stronger. Is she correct, and why?

• She is correct, the iron core will make the magnet stronger, because iron conducts electricity.

Sorry this is the wrong answer. Iron is a good conductor of electricity but no electricity actually flows through the iron core, so it being a good conductor makes no difference.

• She is correct, the iron core will make the magnet stronger because iron is a magnetic material.

This is the correct answer. Well done! Magnetic materials, such as iron, will increase the strength of an electromagnet if used in the core.

• She is incorrect, the iron core will not make the magnet stronger, because iron conducts electricity.

Sorry this is the wrong answer. The iron core certainly will make the magnet stronger.

• She is incorrect, the iron core will not make the magnet stronger because iron is a magnetic material.

Sorry this is the wrong answer. The iron core certainly will make the magnet stronger.

## Question 10

Jane and John have made an electromagnet using a soft iron core with 10 windings of insulated copper wire and a voltage of 1.5V. They found that they could pick up 3 paper clips with this magnet if they were careful. Which of the following changes would not result in more paper clips being picked up?

• Increasing the voltage (and therefore the current).
• Using 15 turns of wire instead of 10.
• Reverse the connections to the battery so that the current flows in the opposite direction.
• Add a resistor in series with the electromagnet.

Solution

Reverse the connections to the battery so that the current flows in the opposite direction. The strength of the magnet produced does not depend on the direction of the current.

## Question 11

A photocopying machine creates a picture by making use of static electricity. Put the following statements about how the process works in the correct order.

1. Paper is given an opposite charge to the toner and pressed onto the plate. This causes the toner to stick to the paper rendering a copy of the picture.
2. A plate is given a charge, an image is projected onto the plate. Where the image was dark, a dark area forms on the plate.
3. Particles of toner are sprayed over the plate and are attracted to the charged areas, but not the neutral areas.
4. Light shining on the plate gives the charges enough energy to leak away. The dark areas of the plate stay charged.
1 2 3 4
3 2 1 4
4 2 3 1
1 3 2 4
1 3 4 2
2 1 4 3
2 4 3 1
2 4 1 3

(Don't see your order in among the options? Check again because the correct order is certainly in there).

Solution

2 4 3 1

## Question 12

A wire is connected to a power pack and placed in the magnetic field of two bar magnets. When the power pack is switched on the wire jumps upwards. What effect will increasing the current in the wire have ?

• There will be no effect because the magnets haven't been changed.
• The wire still moves upwards, but this time the greater current causes it to move more slowly.
• The wire will now move downwards.
• The wire will move upwards more quickly than before.

Solution

The wire will move upwards more quickly than before.

## Question 13

This is the same setup as in question 12.

What can be done to make the wire move downwards ? (Choose two methods from the list)

• increase the current

No. This will just make the wire move upwards faster.

• reverse the current

Wrong Answer. This makes no difference.

• make the wire shorter