11.1 Static Electricity

Figure 1 shows a van der Graaff generator, a device that can reach extremely high voltages.

Figure 1

When the handle is turned, the dome becomes positively charged.

In terms of electron movement, give a reason why the metal dome becomes positively charged.

Calculate the energy transferred to an electron when it passes through a voltage of 180 kV.

Charge of an electron = 1.6 × 10^–19 C

When the van der Graaff generator is fully charged, it stores 3.5 × 10^–8 C of charge.

The metal dome is discharged. A thin metal case is then placed on top of the metal dome, as shown in Figure 2.

Figure 2

A student investigating static electricity charges two balloons and hangs them side by side. They observe the balloons do not hang vertically, as shown in Figure 1.

Figure 1

Explain why the cotton threads are not vertical.

The student charges the balloon by rubbing it with a cloth. The balloon becomes negatively charged.

The student investigates the effect of putting charged balloons on different surfaces. They put one charged balloon against a metal cabinet and one charged balloon against a wall.

A student gives a plastic strip an overall electric charge.

[1]

Figure 1

The electroscope has no overall charge.
The gold leaf has a very small mass and can bend very easily.
The student brings a negatively charged plastic strip near to the cap of the electroscope.

The gold leaf bends away from the metal rod.
Which diagram shows the way that electric charge is now distributed?

[1]

Figure 2a shows another gold leaf electroscope that has been given an overall negative charge.

A student connects the metal cap of the charged electroscope to earth with a piece of wire as shown in Figure 2b.

Explain why the gold leaf has moved.

Figure 3

[2]

State the effect that the electric field of object Q has on object P.

[1]

Figure 13

[1]

Figure 14

A spark jumps between the spheres, discharging sphere M.

Describe what happens in the wire connecting sphere N to earth when the spark jumps between M and N.

[2]

[2]

Figure 15

Draw on Figure 15 the shape and direction of the electric field between the plates.

Figure 16

An acetate strip can be charged positively.

A polythene strip can be charged negatively.

A coulombmeter can be used to measure charge and whether the charge is positive or negative.

Explain how you would use the apparatus in Figure 16 to show that like charges repel and unlike charges attract.

Figure 1

Some paint sprayers give the paint drops a positive charge as they leave the sprayer.

Sprayer X does not charge the paint drops. Sprayer Y gives the paint drops a positive charge.

Explain how charging the paint drops changes the shape of the spray pattern.

[2]

The top plate has a negative electric charge.

The bottom plate has a positive electric charge.

On Figure 3, draw the electric field lines between the two plates and show the direction of this electric field.

A student uses a cloth to give a plastic rod a positive charge.

[3]

The student brings the positively charged rod near to each ball in turn.

                             
Which ball is repelled by the positively charged rod?

[1]

Figure 13 shows part of a cloud, above the ground.

The base of the cloud is negatively charged.

Explain how lightning is produced between the cloud and the Earth.

Your answer should refer to induced charges.

You may add to the diagram in Figure 13 to help your answer.

Figure 14

Explain why transferring fuel can be dangerous and how the use of metal wires makes the process much safer.