IGCSE Physics Electricity & circuits topical questions

Answer these basics of static and current electricity.

1. (a)State the two kinds of electric charge and what they do when brought near each other.[1]
2. (b)Name the particles that move when a solid is charged by friction.[1]
3. (c)State the unit of current.[1]
4. (d)Name the meter used to measure potential difference.[1]

A circuit contains a 3.0 V battery, a lamp and an ammeter in series. The ammeter reads 0.60 A.

1. (a)State the current at every point in this series circuit.[1]
2. (b)Calculate the resistance of the lamp.[2]
3. (c)State where a voltmeter should be connected to measure the lamp’s p.d.[1]

A student rubs a balloon on a wool jumper. The balloon becomes negatively charged and sticks to a wall.

1. (a)Explain how the balloon became negatively charged.[2]
2. (b)The wall is neutral. Explain why the charged balloon still sticks to it.[2]

A student connects three components in turn to a variable power supply and records the current at each voltage.

1. (a)Name the component whose I–V graph is a straight line through the origin.[1]
2. (b)Describe the shape of a filament lamp’s I–V graph at high voltage, and explain why.[2]
3. (c)State the unit of resistance.[1]

A 12 V battery drives two resistors of 4.0 Ω and 8.0 Ω connected in series.

1. (a)Calculate the combined resistance.[1]
2. (b)Calculate the current flowing from the battery.[2]
3. (c)Calculate the p.d. across each resistor and show the two values add to 12 V.[2]

The same two resistors (4.0 Ω and 8.0 Ω) are reconnected in parallel across the same 12 V battery.

1. (a)State the p.d. across each resistor.[1]
2. (b)Calculate the current in each branch.[2]
3. (c)Calculate the total current from the battery and the combined resistance.[3]

A house owner runs a 2.4 kW electric heater and a 0.60 kW television for 3.0 hours. Electricity costs 28 cents per kW h.

1. (a)Calculate the total energy transferred in kW h.[2]
2. (b)Calculate the total cost.[2]
3. (c)State what 1 kW h represents physically.[1]

A 12 V battery drives a 2.0 Ω resistor in series with a parallel pair made of two 6.0 Ω resistors.

1. (a)Calculate the combined resistance of the parallel pair.[1]
2. (b)Calculate the total resistance of the circuit and the current from the battery.[2]
3. (c)Calculate the p.d. across each part of the circuit and show the values add to 12 V.[3]

Two small conducting spheres hang close together on insulating threads. Sphere A carries a positive charge; sphere B is uncharged.

1. (a)Describe the electric field lines around sphere A.[1]
2. (b)Explain why sphere B, though uncharged, is attracted towards A.[2]
3. (c)B is now touched against A and removed. State the sign of the charge on each sphere and the new force between them.[2]

A hair dryer rated at 230 V, 1.2 kW is used on the mains.

1. (a)Calculate the normal current through the hair dryer.[2]
2. (b)Choose the most suitable fuse from 3 A, 13 A and 30 A, and justify your choice.[2]
3. (c)The live wire inside the dryer breaks and touches the metal grille. Explain, step by step, how the earth wire and fuse protect a user who then touches the grille.[2]

A potential divider is made from a 6.0 V battery and two fixed resistors: R₁ = 200 Ω on top and R₂ = 400 Ω below. The output is taken across R₂.

1. (a)Calculate the current through the divider.[2]
2. (b)Calculate the output voltage across R₂.[3]
3. (c)R₂ is replaced by a thermistor whose resistance falls when warmed. State and explain what happens to the output voltage when the thermistor warms.[2]

An electric kettle rated at 230 V, 2.0 kW is used for 4.0 minutes each morning. Take the mains voltage as 230 V. Electricity costs 30 cents per kW h.

1. (a)Calculate the normal current of the kettle, to 2 significant figures.[2]
2. (b)Show that 30 mornings of boiling transfers about 4.0 kW h of energy.[2]
3. (c)Calculate the total cost of those 30 boils.[1]
4. (d)Calculate the energy transferred in one 4.0-minute boil, in joules.[1]