Static electricity

Figure 19 shows two metal plates.

The plates are charged by a very high voltage (potential difference).

Draw, on Figure 19, the shape and direction of the electric field between the two plates.

Figure 20 shows a device that removes small particles of soot from sooty air.

There is a large potential difference between the metal tube and the metal rod in the centre of the tube.

This large potential difference causes the soot particles to gain a negative charge as they pass between the rod and the tube.

The soot particles have

Explain why, in Figure 20, the charged soot particles move towards the metal tube.

When the soot particles reach the metal tube, the charge on them changes.

State how the charge on them changes.

The metal tube does not become charged when the soot particles reach it.

Explain why the metal tube does not become charged.

There is a current of 2.5 mA in a circuit.

Calculate the amount of charge that moves past a point in the circuit in 80 seconds.

State the unit of charge.

If you’re taking GCSE (9–1) Combined Science or GCSE (9–1) Physics, you will need these equations:

HT = higher tier

distance travelled = average speed × time
acceleration = change in velocity ÷ time taken	a v t u
force = mass × acceleration	F = m × a
weight = mass × gravitational field strength	W = m × g
HT momentum = mass × velocity	p = m × v
change in gravitational potential energy = mass × gravitational field strength × change in vertical height	∆GPE = m × g × ∆h
kinetic energy = 1/2 × mass × (speed)2	KE 21 m v2
efficiency = useful energy transferred by the devicetotal energy supplied to the device
wave speed = frequency × wavelength	v = f × λ
wave speed = distance ÷ time	v xt
work done = force × distance moved in the direction of the force	E = F × d
power = work done ÷ time taken	P Et
energy transferred = charge moved × potential difference	E = Q × V
charge = current × time	Q = I × t
potential difference = current × resistance	V = I × R
power = energy transferred ÷ time taken	P Et
electrical power = current × potential difference	P = I × V
electrical power = (current)2 × resistance	P = I2 × R
density = mass ÷ volume	mV

force exerted on a spring = spring constant × extension F = k × x

If you’re taking GCSE (9–1) Physics, you also need these extra equations:

moment of a force = force × distance normal to the direction of the force
pressure = force normal to surface ÷ area of surface	P FA
HT potential difference across secondary coilpotential difference across primary coil nnumber of turns in primary coilumber of turns in secondary coil	VVpS NNpS
to calculate pressure or volume for gases of fixed mass at constant temperature	P1 × V1 = P2 × V2
HT pressure due to a column of liquid liquid × gravitational field strength= height of column × density of	P = h × ρ × g

Figure 5 shows two metal plates.

The plates are charged by a very high voltage (potential difference).

Draw, on Figure 5, the shape and direction of the electric field between the two plates.

Figure 6 shows a device that removes small particles of soot from sooty air.

There is a large potential difference between the metal tube and the metal rod in the centre of the tube.

This large potential difference causes the soot particles to gain a negative charge as they pass between the rod and the tube.

The soot particles have

Explain why, in Figure 6, the charged soot particles move towards the metal tube.

When the soot particles reach the metal tube, the charge on them changes.

State how the charge on them changes.

The metal tube does not become charged when the soot particles reach it.

Explain why the metal tube does not become charged.

There is a current of 2.5 mA in a circuit.

Calculate the amount of charge that moves past a point in the circuit in 80 seconds.

State the unit of charge.

A student rubs two balloons with a dry cloth.

The balloons become positively charged.

The student hangs the charged balloons using strings, as shown in Figure 5.

Use words from the box to complete the sentences.

The balloons have the same charge.

This means that these balloons_........ each other.

The charged particles transferred from the balloons to the cloth are

The cloth is left with a_........ charge.

The unit of charge is the_........ .

One of the charged balloons is moved so it nearly touches a wall, as shown in Figure 6.

The balloon then sticks to the wall.

Explain why the balloon sticks to the wall.

You may add to the diagram to help your answer.

Figure 7 shows a positively charged metal sphere above the ground.

The metal sphere can be discharged by connecting the sphere to the ground with a metal wire.

Explain how this would discharge the sphere.

This question is about static electricity and electric fields.

Figure 1 shows three charged objects, X, Y and Z.

Y has a positive charge and is held stationary.

The charge on Y causes X and Z to move in the directions of the arrows.

Which row of the table is correct for the charges on X and Z?

Give the meaning of the term electric field.

Figure 2 shows the electric field around a point charge.

State how Figure 2 gives evidence that the point charge is positive.

In Figure 2, x is the distance from the point charge.

State how Figure 2 gives evidence that the electric field strength decreases as x increases.

Figure 3 shows a graph of electric field strength against distance x.

The equation relating electric field strength to distance, x, is

A is a constant.

Using data from the graph in Figure 3, calculate the value of A when x = 3 cm.

This question is about static electricity.

Figure 1 shows a plastic comb picking up small pieces of paper.

The comb picks up the paper because the comb has extra

Figure 2 shows a person touching a charged dome.

The person’s hair is standing on end.

Explain how electric charge causes the hair to spread out, as shown in Figure 2.

The person lets go of the charged dome.

The charge on the person’s hair is 10 μ C.

The charge on the dome is 25 μ C.

Calculate the percentage of charge on the hair compared with on the dome.

Use the equation

percentage of charge on the hair =_........

Draw one straight line from each example of electrostatic charges in action to their descriptions.

electrostatic charges in action description

Figure 1 shows a prize that is made from a metal star on a plastic base.

A person starts to clean the prize by rubbing the plastic base with a dry cloth.

The plastic base becomes positively charged and the cloth becomes negatively charged.

The plastic base has

Explain why the cloth has become negatively charged.

The person then holds the metal star and rubs it with the charged cloth.

The cloth loses its charge.

Explain why the cloth loses its charge.

The charged plastic base attracts some dust from the air.

Figure 2 shows a magnified view of part of the surface of the plastic base and a dust particle.

Some of the charges on the plastic base are shown but the charges induced on the dust particle are not shown.

Draw the charges induced on the dust particle in Figure 2.

Which of the following shows the electric field around a point charge?

State one way of giving a plastic rod a static electric charge.

A cleaning company uses an electric sprayer to produce a cloud of disinfectant inside a bus.

The sprayer gives a negative electric charge to each droplet in the cloud of disinfectant.

The droplets in the cloud of disinfectant have a negative charge because the sprayer

Figure 16 shows the shape of the clouds of droplets in the disinfectant from two sprayers.

cloud from sprayer 1 cloud from sprayer 2

Figure 16

Sprayer 1 gives a negative charge to each droplet.

Sprayer 2 does not give any charge to the droplets.

Explain the difference in the shape of the two clouds.

Figure 17 shows a cloud of disinfectant, containing charged droplets, moving towards a seat in the bus.

Explain how charging the droplets in the cloud of disinfectant makes sure that every part of the seat is disinfected.

*(d) Figure 18 shows an aeroplane being refuelled.

The fuel passes through a pipe into fuel tanks in the wings.

The fuel is very flammable.

A build-up of static electric charge can be dangerous while the aeroplane is being refuelled.

Explain

• why the build-up of static electric charge would be dangerous

• how the danger is reduced.

This question is about static electricity.

Draw on Figure 1 the shape and direction of the electric field due to the positive point charge.

Figure 1

A student rubs a plastic ruler against a woolly jumper.

The student tests the ruler and finds it has a positive charge.

Explain how the ruler becomes positively charged.

An insecticide sprayer charges droplets of insecticide.

Figure 2 shows the sprayer being used to spray a leaf.

The leaf is connected to the ground (earthed).

Explain how charging the droplets helps to make sure that the leaf gets covered with insecticide.

You may add to Figure 2, including the sign (+ or −) of any charges, to help your answer.

Figure 13 shows a negatively charged metal sphere, M.

Sphere M is negatively charged because it has

A metal sphere, N, is connected to earth by a wire.

N is moved near to M as shown in 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.

Describe a use of earthing in everyday life.

Your answer should state the use and describe why earthing is needed.

Figure 15 shows two parallel metal plates.

The plates are charged using a very high voltage.

metal plate

+ + + + + + + + + + + + + + + + + + + +

– – – – – – – – – – – – – – – – – – – –

metal plate

Figure 15

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

*(c) This question is about electrostatic charges and the forces between them.

Figure 16 shows some apparatus that can be used to show that like charges repel and unlike charges attract.

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.

A student gives a plastic strip an overall electric charge.

Describe one way that the student can give the plastic strip an overall electric charge.

Figure 1 shows a gold leaf electroscope that can be used to investigate static electricity.

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?

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.

Two small objects, P and Q, are each given an electric charge.

Figure 3 represents the electric fields around the objects, P and Q.

Use information from Figure 3 to give two differences between the charge on P and the charge on Q.

Object P and object Q are held near to each other so that their electric fields interact with each other.

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

This question is about static electricity.

A student has a rubber balloon tied to a long piece of cotton thread.

The student gives the balloon an overall electrostatic charge.

Describe one way that the student could give the balloon an overall electrostatic charge.

The student gives the balloon an overall negative charge.

Which of these sentences explains why the overall charge on the balloon is negative?

The student charges another balloon on a long thread.

Explain how the student can show that the two balloons have the same type of charge.

Figure 26 shows a plastic block and a metal disc with an insulating handle.

The top surface of the plastic block has a negative charge.

The metal disc has no overall electric charge.

A student uses the insulating handle to hold the metal disc above the plastic block.

Which of these diagrams shows how the charge is distributed on the metal disc?

The student keeps holding the metal disc above the charged plastic block and taps the metal disc with a finger.

This earths the metal disc for a short time.

Explain why the disc now has an overall positive charge.

Figure 27 shows the charges on part of the metal disc and the plastic block.

On Figure 27, draw lines to show the shape and direction of the electric field between the metal disc and the plastic block.

Equations

This question is about static electricity.

A student has a rubber balloon tied to a long piece of cotton thread.

The student gives the balloon an overall electrostatic charge.

Describe one way that the student could give the balloon an overall electrostatic charge.

The student gives the balloon an overall negative charge.

Which of these sentences explains why the overall charge on the balloon is negative?

The student charges another balloon on a long thread.

Explain how the student can show that the two balloons have the same type of charge.

Figure 9 shows a plastic block and a metal disc with an insulating handle.

The top surface of the plastic block has a negative charge.

The metal disc has no overall electric charge.

A student uses the insulating handle to hold the metal disc above the plastic block.

The student keeps holding the metal disc above the charged plastic block and taps the metal disc with a finger.

This earths the metal disc for a short time.

Explain why the disc now has an overall positive charge.

Figure 10 shows the charges on part of the metal disc and the plastic block.

On Figure 10, draw lines to show the shape and direction of the electric field between the metal disc and the plastic block.

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

Explain how the rod becomes positively charged.

Figure 12 shows four light balls, Q, R, S and T. Each ball is suspended on a nylon string. Balls Q, R and T are coated with a conducting material. Ball S is an insulator.

Q and S have no charge, R is positively charged and T is negatively charged.

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

Which ball is repelled by the positively charged rod?

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.

*(c) Figure 14 shows fuel being transferred to an aeroplane.

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

Figure 1 shows a paint sprayer.

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

The paint drops have a positive charge because the sprayer

Figure 2 shows the spray pattern from two different paint sprayers.

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.

Sprayer Y is used in a factory to paint a metal object.

The object hangs by a metal wire that is connected to earth.

Explain why a metal wire is used to connect the object to earth.

Figure 3 shows two charged metal plates.

Figure 3

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 rubs a plastic comb with a dry cloth to give the comb a positive electric charge.

Figure 6 shows the charged plastic comb picking up small pieces of paper.

(Source © GIPhotoStock/SCIENCE PHOTO LIBRARY)

Figure 6

Explain how rubbing the comb with a dry cloth gives the comb a positive electric charge.

Explain how the positively-charged plastic comb picks up the small pieces of paper.

Which of these diagrams shows the shape and direction of the electric field around a positive point charge?

Figure 7 shows two metal spheres.

Metal sphere A is fixed to a table. Metal sphere B can be moved.

Metal sphere B is placed at a short distance from metal sphere A.

sphere A fixed
sphere B can be moved

Both spheres are insulated from the table and given a negative charge.

The force between the charged spheres is measured.

Explain, in terms of electric fields, why a force is exerted on sphere B.

Sphere B is moved and the force between the spheres is measured at several different distances.

Figure 8 is a graph of force on sphere B against distance between the centres of the spheres.

distance between centres of spheres in cm

Figure 8

Describe how the force on sphere B varies with the distance between the centres of the spheres.