Static Electricity (AQA GCSE Physics)

Figure 1 shows a Van de Graaff generator that is used to make pupils’ hair stand on end the world over.

Figure 1

A negatively charged object is placed at each of the positions shown below: A, B, C, and D.

At which point would the object experience the greatest force?

Position ________

Figure 2 shows a student touching the dome of a charged Van de Graaff generator.

Figure 2

When the potential difference between the dome and the student reached 20 kV, a spark jumped to the student from the dome.

This spark converted 50 mJ of energy into heat, light and sound.

Calculate the charge carried by the spark.

The spark transfers the charge to the student in a time of 1.5 ms.

Calculate the current in the spark.

Figure 3 shows a youth jumping on a trampoline while wearing socks.

Figure 3

As the youth bounces, friction between his socks and the trampoline cause him to become negatively charged.

The youth’s head is shown as a circle in the diagram below.

The student’s head is negatively charged.

Draw the electric field pattern around the youth’s head.

When the youth stops jumping and touches the metal side of the trampoline, he receives an electric shock.

Explain why.

The youth got fed up with constantly receiving shocks and decided to wear a grounded wrist strap when bouncing.

This severely hampered his ability to perform acrobatic manoeuvres but did prevent the shocks.

A grounded wrist strap contains a thin copper wire which connects the youth’s wrist to the trampoline frame.

Suggest why the grounded wrist strap prevents shock.

Figure 4 shows a children’s playground slide. It is made from plastic.

Figure 4

As a child slides down the slide, she becomes electrostatically charged.

Explain why.

When the child gets to the bottom of the slide, her hair is standing on end.

What conclusion can be made about the electrical charge on the child’s head from this observation?

Give a reason for your answer.

A student rubs a glass rod with a piece of polystyrene.

The glass rod becomes positively charged.

The student placed the glass rod onto a balance, as shown in Figure 5 below.

A piece of insulating material was placed between the glass rod and the balance.

Figure 5

The student then rubbed a pvc rod with a pair of nylon tights and held it near to, but not touching the glass rod on the balance. 

The reading on the balance decreased.

Figure 6

Explain why the reading on the balance decreases.

When the student brings the two rods closer together, the reading on the balance decreases still further.

What can the student conclude from this observation?

A student carried out an experiment to investigate the effect of bringing charged rods near to each other, as shown in Figure 7 below. 

Nylon rod AB was rubbed with a cloth, and then suspended from a clamp stand, so that it was free to rotate.

Polythene rod CD was also rubbed with a cloth, then brought close to rod AB. Care was taken to ensure the rods did not touch.

Figure 7

End C was brought near to end B. The rods moved towards each other.

The experiment was repeated with two identical nylon rods.

Explain what would happen when one rod was brought near to the other one.