[Maximum number: 1]

What is a correct value for the charge on an electron?

A

$1.60 \times 10^{-12} \mu \mathrm{C}$

B

$1.60 \times 10^{-15} \mathrm{mC}$

C

$1.60 \times 10^{-22} \mathrm{kC}$

D

$1.60 \times 10^{-24} \mathrm{MC}$

[Maximum number: 2]

Ion-thrust engines can power spacecraft. In this type of engine, ions are created in a chamber and expelled from the spacecraft. The spacecraft is in outer space when the propulsion system is turned on. The spacecraft starts from rest.

The mass of ions ejected each second is $6.6 \times 10^{-6} \mathrm{~kg}$ and the speed of each ion is $5.2 \times 10^{4} \mathrm{~m} \mathrm{~s}^{-1}$ . The initial total mass of the spacecraft and its fuel is 740 kg . Assume that the ions travel away from the spacecraft parallel to its direction of motion.

(a)

In practice, the ions leave the spacecraft at a range of angles as shown.

[ 2 ]

(i)

Outline why the ions are likely to spread out.

[ 2 ]

[Maximum number: 2]

Ion-thrust engines can power spacecraft. In this type of engine, ions are created in a chamber and expelled from the spacecraft. The spacecraft is in outer space when the propulsion system is turned on. The spacecraft starts from rest.

The mass of ions ejected each second is $6.6 \times 10^{-6} \mathrm{~kg}$ and the speed of each ion is $5.2 \times 10^{4} \mathrm{~m} \mathrm{~s}^{-1}$ . The initial total mass of the spacecraft and its fuel is 740 kg . Assume that the ions travel away from the spacecraft parallel to its direction of motion.

(a)

In practice, the ions leave the spacecraft at a range of angles as shown.

[ 2 ]

(i)

Outline why the ions are likely to spread out.

[ 2 ]

[Maximum number: 1]

Which is a vector quantity?

A

Pressure

B

Electric current

C

Temperature

D

Magnetic field

[Maximum number: 1]

A small positively charged sphere is suspended from a thread and placed close to a negatively charged rod. When the thread is at $45^{\circ}$ to the vertical the system is in equilibrium. The weight of the sphere is W and the magnitude of the electrostatic force between the rod and the sphere is F.

(not to scale)

What is the magnitude of W compared with the magnitude of F ?

A

$W=\sqrt{2} F$

B

$F<W<\sqrt{2} F$

C

W=F

D

W>F

[Maximum number: 2]

The air in a kitchen has pressure $1.0 \times 10^{5} \mathrm{~Pa}$ and temperature $22^{\circ} \mathrm{C}$ . A refrigerator of internal volume $0.36 \mathrm{~m}^{3}$ is installed in the kitchen.

(a)

The refrigerator door is closed. The air in the refrigerator is cooled to $5.0^{\circ} \mathrm{C}$ and the number of air molecules in the refrigerator stays the same.

[ 2 ]

(i)

Comment on the magnitude of the force in (b)(ii).

[ 2 ]

[Maximum number: 1]

A particle X has a small positive charge and is free to move. Y has a large positive charge and is fixed. X is initially moving towards Y .

Y exerts an electric force F on X. Gravitational forces are negligible.
The magnitude of the force exerted by X on Y is

A

zero.

B

less than the magnitude of F.

C

equal to the magnitude of F.

D

greater than the magnitude of F.

[Maximum number: 1]

Two charged parallel metal plates, X and Y , are separated by a distance of $2.0 \mathrm{~m} . \mathrm{X}$ is at a potential of -150 V and Y is at a potential of +150 V .

Point P is midway between X and Y . Which of the following gives the electric field strength at point P ?

A

$150 \mathrm{Vm}^{-1}$ to the right

B

$150 \mathrm{Vm}^{-1}$ to the left

C

$300 \mathrm{Vm}^{-1}$ to the right

D

$300 \mathrm{Vm}^{-1}$ to the left

[Maximum number: 5]

C1. This question is about mobile phones.
(a) The diagram shows the cell network used in a mobile phone system.

(i) A mobile phone is in cell C . State how the strength of the signal from the transmitter in this cell compares with the signals from surrounding cells.
(ii) Explain why mobile phone companies must use a specified range of frequencies within each cell.
(iii) The range of frequencies used allows approximately 800 signals to be transmitted simultaneously. However, a maximum of 400 connections can be made. State why this is the case.
(b) Suggest two reasons why the general public may be concerned about the use of mobile phones.

[Maximum number: 1]

Which diagram shows a correct equipotential line due to two point charges X and Y of opposite sign?

A

B

C

D