WE LOVE PHYSICS OLE OLE RAYA

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 decrease diameter

  decrease length

• B decrease diameter

  increase length

• C increase diameter

  decrease length

• D increase diameter

  increase length

Which statement describes the nature and a property of all β-particles?

• A electrons can travel through a vacuum

• B electrons stopped by a thin sheet of paper

• C helium nuclei can travel through a vacuum

• D helium nuclei stopped by a thin sheet of paper

The diagram shows a battery connected to two resistors. Four students separately measure the electromotive force (e.m.f.) of the battery, the current in the resistors, and the potential difference (p.d.) across resistor R. Which row shows values with their correct units?

• A emf = 3.0 A

  current = 0.30 V

  p.d. = 1.5 A

• B emf = 3.0 A

  current = 0.30 A

  p.d. = 1.5 V

• C emf = 3.0 V

  current = 0.30 V

  p.d. = 1.5 A

• D emf = 3.0 V

  current = 0.30 A

  p.d. = 1.5 V

A student uses a length of wire as a resistor. He makes a second resistor from the same material. To be certain of making a second resistor of higher resistance, he should use a piece of wire that is

• A longer and thicker.

• B longer and thinner.

• C shorter and thicker.

• D shorter and thinner.

What is the unit of electromotive force (e.m.f.)?

• A ampere

• B newton

• C ohm

• D volt

A teacher wishes to show the production of electrostatic charges. She holds a rod and rubs it with a cotton cloth. A copper rod, a glass rod, a plastic rod and a steel rod are available. Which two rods would both be suitable to use?

• A a copper rod and a glass rod

• B a glass rod and a plastic rod

• C a plastic rod and a copper rod

• D a plastic rod and a steel rod

Which group contains only good electrical conductors?

• A air, carbon (graphite), plastic

• B air, gold, mercury

• C carbon (graphite), copper, mercury

• D copper, gold, plastic

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?

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A negatively charged rod is held close 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?

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A positively charged plastic rod is placed just above a thick metal plate. The metal plate rests on an insulator and is connected to the earth by a wire. A student disconnects the earthing wire and then removes the positively charged rod. The experiment is repeated. This time the student removes the positively charged rod and then removes the earthing wire. Which statement is correct?

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

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

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

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