Programme 19: Circuits

Activity Sheet 1

Programme Questions

Current and Voltage

1. What happens to the brightness of light bulbs as more are added:
a) in series?
b) in parallel?

2. What happens to the total current flowing from the power supply as more bulbs are added:
a) in series?
b) in parallel?

3. What is the relationship between the supply voltage and the voltage across each component:
a) in a series circuit?
b) in a parallel circuit?

Ohm’s Law

1. If a graph of the voltage across a wire is plotted against the current flowing through it:
a) What shape is the graph?
b) What does the gradient of the graph tell you about the wire?
c) What law does the graph show is true for a wire?

2. What shape is a graph of voltage against current for a light bulb?

Changing Resistance

1. If pieces of wire are the same length and thickness, but made of different metal, will their resistance be the same or different?

2. The resistance of a piece of wire is measured. If a longer piece of the same wire is tested will it have:
a) the same resistance
b) lower resistance
c) higher resistance?

3. Draw a diagram of a metal lattice showing the positive ions and the electrons flowing through the lattice when an electric current flows through the metal:
a) for a wire
b) for a thicker wire, which has lower resistance

4. What happens to the resistance of a wire as it is cooled?

5. Explain your answer to question 4 by describing what happens to the lattice of positive ions and the sea of free electrons.