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Activity 2: Circuit diagrams

When electricity flows through a circuit it can be used to light up a globe or make an electric motor work. A circuit diagram is used to show you which parts make up the circuit and in what order.

Can you connect up circuits using a diagram with symbols as your guide?

What to use
Batteries, globes, switch, wires, ammeter, electric motor.
What to do
Trouble shooting
Quite often a circuit will not work the first time. If a circuit does not work, you need to check that the globe is not 'blown', the globe is screwed in tightly, the battery is not flat, all wires are connected properly, or that there is not a break in one of the wires or other parts of the circuit. Or perhaps the circuit is one that does not work even when connected according to the circuit diagram.

  1. Connect up the circuits in the diagrams. Use the results to answer the questions.
  1. Which circuit has the brighter globe? Why do you think this occurs?
    Circuit diagram A and B
  2. Which circuit has the brighter globe(s)? Why do you think they are brighter?
    Circuit diagram C and D
  3. Which circuit has the brighter globes? Why do you think this happens?
    Circuit diagram E and F
  4. How do you think the amount of electricity flowing in a circuit is affected by the number of batteries (see Question 2) and by the number of globes (see Question 3)? You could connect an ammeter (which measures current) in the circuit to check your ideas.
  5. How is the speed of an electric motor affected by the number of batteries in the circuit?
    Circuit diagram G
  6. Try these two circuits. If you wanted to light up two globes as brightly as possible using one battery, which is the better way to do it?
    Circuit diagram H and J
  7. Predict which of each pair of circuits in the diagram will have the brighter globes. Construct these circuits and find out if your predictions were correct.
    Circuit diagrams A to F activity
Series and parallel circuits
Parallel and series circuits

In a series circuit (left-hand side) the current flows through one globe after another, each being able to make use of only a part of the energy carried by the current. In a series circuit, if one of the globes blows and current can no longer pass through it, the current cannot flow in the circuit at all.

In a parallel circuit (right-hand side) the current can pass simultaneously through each globe and the energy of the current is available to each globe. In a parallel circuit, if one of the globes blows and current can no longer pass through it, the current can continue to flow through the rest of the circuit.

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