GCSE Physics Circuits questions by topic

Name the meter used to measure each quantity, and state where it is placed in the circuit.

1. (a)Current.[2]
2. (b)Potential difference.[2]

Complete the sentences about series circuits.

1. (a)The current is the … at every point in a series circuit.[1]
2. (b)The p.d.s across the components … to equal the supply p.d.[1]
3. (c)The total resistance is found by … the separate resistances.[1]
4. (d)Adding another resistor in series … the total resistance.[1]

A torch lamp draws 0.30 A from two 1.5 V cells in series.

1. (a)State the supply p.d.[1]
2. (b)Calculate the charge that flows in 2.0 minutes.[2]
3. (c)Calculate the lamp’s resistance.[2]

Sketch or describe the I–V graph of each component.

1. (a)A fixed resistor at constant temperature.[1]
2. (b)A filament lamp.[1]
3. (c)A diode, marking the direction that conducts.[1]
4. (d)State what the graph of the fixed resistor tells you about its resistance.[1]

A student measures the resistance of a nichrome wire at lengths of 0.20 m, 0.40 m, 0.60 m, 0.80 m and 1.00 m.

1. (a)Describe the pattern in the results.[2]
2. (b)Predict the resistance of 1.40 m of the same wire.[1]
3. (c)State one variable that must be controlled, and how.[2]

A 12 V battery drives 4 Ω and 2 Ω resistors connected in series.

1. (a)Calculate the total resistance.[1]
2. (b)Calculate the current.[2]
3. (c)Calculate the p.d. across each resistor.[2]
4. (d)Check that your p.d.s agree with the supply.[1]

A 12 V supply is connected across 4 Ω and 6 Ω resistors in parallel.

1. (a)State the p.d. across each resistor.[1]
2. (b)Calculate the current in each branch.[2]
3. (c)Calculate the supply current.[1]
4. (d)Calculate the total resistance and show it is less than either branch.[3]

Explain the shape of a filament lamp’s I–V graph.

1. (a)Describe the shape for positive p.d.[2]
2. (b)Explain why the resistance changes as the current grows.[3]
3. (c)State what the graph looks like for negative p.d., and why.[1]

A greenhouse uses a thermistor in a potential divider with a fixed resistor to switch a heater on when it gets cold.

1. (a)State how the thermistor’s resistance changes as the greenhouse cools.[1]
2. (b)Explain how the p.d. across the thermistor changes as it cools.[3]
3. (c)Explain how the circuit uses this to switch the heater.[2]

This question is about the I–V characteristics required practical.

1. (a)Draw or describe the circuit used, naming every meter and its placement.[3]
2. (b)State the independent and dependent variables.[2]
3. (c)Explain why readings should be taken quickly and with modest currents.[2]

A 24 V supply drives a 6 Ω resistor in series with a parallel pair made of 6 Ω and 3 Ω.

1. (a)Calculate the resistance of the parallel pair.[2]
2. (b)Calculate the total resistance and the supply current.[2]
3. (c)Calculate the p.d. across the parallel pair.[2]
4. (d)Calculate the current in each branch of the pair.[2]

A student suggests: “Adding more resistors to a circuit always increases its total resistance.”

1. (a)State when the student is right, with a numerical example.[2]
2. (b)State when the student is wrong, with a numerical example.[2]
3. (c)Explain, using the model of charge flow, why the parallel case behaves as it does.[3]

A 230 V mains lamp is labelled 60 W, 230 V, so its hot resistance is about 880 Ω. Measured cold with a meter it reads only 75 Ω.

1. (a)Verify the hot resistance from the label (R = V² ÷ P is not needed: use I = P ÷ V first).[3]
2. (b)Calculate the ratio of hot to cold resistance.[1]
3. (c)Explain the difference using the filament’s behaviour.[2]
4. (d)State one consequence for the lamp at switch-on.[2]

Design and evaluate an investigation into how the resistance of a thermistor changes with temperature.

1. (a)State the independent and dependent variables.[2]
2. (b)Describe a method using a water bath, naming both meters and their placements.[3]
3. (c)State one control variable and one source of error with an improvement.[3]