A polythene rod is rubbed with a cloth. The rod and the cloth both become charged as electrons move between them. The rod becomes negatively charged. Which diagram shows how the rod becomes negatively charged, and the final charge on the cloth.

• A

• B

• C

• D

Two balloons, X and Y, are suspended by insulating threads. They are each held near a negatively charged balloon. The balloons hang as shown.

• A

• B

• C

• D

Two similar balloons hang side by side, on insulating threads, a short distance apart. They are both rubbed with the same dry cloth and become charged. Which diagram shows how the balloons hang after charging?

• A

• B

• C

• D

A negatively charged rod is held to one side of a metal sphere. The other side of the sphere is earthed. Which diagram shows the distribution of charge on the metal sphere?

• A

• B

• C

• D

Which statement is correct?

• When the earthing wire is disconnected first, the metal plate becomes positively charged

• When the earthing wire is disconnected first, the metal plate becomes negatively charged

• When the plastic rod is removed first, the metal plate becomes positively charged

• When the plastic rod is removed first, the metal plate becomes negatively charged

A wire has a certain electrical resistance. The diameter and length of the wire may be changed. Which pair of changes must cause the resistance of the wire to increase?

• A

• B

• C

• D

The table described four different resistance wires. They are all made from the same metal. Which wire has the smallest resistance?

• A

• B

• C

• D

What is the unit of electromotive force?

• ampere

• newton

• ohm

• volt

What is the unit of electrical power?

• ampere

• joule

• volt

• watt

Four students are each given an identical resistor and asked to find its resistance. They each measure the potential difference across the resistor and the current in it. One student makes a mistake. Which row shows the results of the student that makes a mistake?

• A

• B

• C

• D