Access tuition Static electricity

Question 1

The student connects the two resistors in the diagram above in parallel.
What happens to the total resistance of the circuit?

Give a reason for your answer [2]

Answer 1

It decreases
because there is more than one path for charge to flow.

Question 2

Explain why the potential difference across the thermistor changes as the
temperature in the house decreases.[2]

Answer 2

(potential difference) increases

(because thermistor) resistance increases

Question 7

The negatively charged student touches a metal tap and receives an electric shock.
Explain why

Answer 7

there is a potential difference between the student and the tap
do not accept the tap / sink is charged

which causes electrons / charges to transfer from the student
which earths the charge

Question 8

Some carpets have thin copper wires running through them. The student is
less likely to receive an electric shock after walking on this type of carpet.
Suggest why.

Answer 8

copper has a low resistance

no potential difference between student and tap

Question 9

Explain how rubbing an acetate rod with a cloth causes the rod and cloth to become
charged.[4]

Answer 9

friction (between cloth and rod) causes
* electrons (to) move
* from the acetate rod or to the cloth
* (net) charge on cloth is now negative
* (net) charge on rod is now positive.

Question 10

A company that produces bottles of mouthwash found a problem with the automatic filling system.

As the bottles go towards the filler, they move around on the conveyer belt and become
electrostatically charged. This causes the stream of mouthwash to move sideways, missing

the open top of the bottle.
The company came up with a solution to the problem. Before the bottles reach the filler,
they pass through a stream of ionised air. The ions in the air neutralise the charge on the
bottles.

(i) Explain why the plastic bottles become charged.
_
(2)
(ii) What is an ion?

(1)
(iii) Earthing the conveyor belt with a conducting wire would not have solved this problem.
Give a reason why.
___
(1)

Answer 10

friction between bottles and conveyor belt / (plastic) guides

1
charge transfers between bottles and conveyor belt / (plastic) guides

electrons move onto / off the bottles

1

(ii) an atom that has lost / gained electron(s)

(iii) charge will not (easily) flow off the conveyor bel

Question 11

Electricity end topic test

Explain why a plug needs a live and neutral wire?

Answer 11

A live connects the alternating potential difference from the main supply.
A neutral wire completes the circuit.