Programme 19: Circuits

Answers to Activity Sheet 1

Activity 1 Programme Questions

Current and Voltage

1. a) As more light bulbs are added in series they all become dimmer.
b) As more light bulbs are added in parallel they all stay equally bright.

2. a) As more light bulbs are added in series the total current from the supply reduces.
b) As more light bulbs are added in parallel the total current from the supply increases.

3. a) In a series circuit the supply voltage equals the sum of the voltages across each of the individual components.
b) In a parallel circuit the supply voltage equals the voltage across each of the components.

Ohm’s Law

1. a) The graph of V against I for a wire is a straight line through the origin.
b) The gradient of the V–I graph tells you the resistance of the wire.
c) The graph shows Ohm’s Law is true for a wire.

2. The graph of voltage against current for a light bulb is a curve.

Changing Resistance

1. Different

2. A longer piece of wire will have a higher resistance.

3. a) diagram of wire
b) diagram of thicker wire

4. If a wire is cooled its resistance will decrease.

5. As a wire is cooled its resistance will decrease because the positive metal ions forming the lattice will vibrate less. Therefore the electrons will make fewer collisions as they move through the lattice.