Monday, 3 December 2012


1. The positive terminal of a dry cell is represented by a "+".
2. The negative terminal is represented by a "-".
3. The different components are connected in an electric circuit to light up a bulb.
4. The circuit diagrams below are used to show how the components of a circuit are connected.

 5. There are two types of circuits:

(a) Series Circuits

The bulbs in a series circuit are arranged in a row.
  • When two or more bulbs are connected one after another in a series, they are connected in series.
  • Electricity flows in one path in this kind of circuit. In the above circuit, electricity flows from positive terminal "+" to negative terminal "-".

Electric current does not flow through the connecting wires and the bulbs do not light up if:
(a) any of the bulbs is removed
(b) any connection in the circuit is broken
(c) any bulb is fused ( spoilt )

  • All bulbs do not light up because electric current cannot flow through the path.
  • When one of the bulb is removed or spoilt , the circuit is broken. All bulbs are affected.
  • If similar bulbs are used, all the bulbs in a series circuit have the same brightness.
  • If the number of bulbs is increased, the brightness of the bulbs decreases.
(b) Parallel Circuits

The bulbs in parallel circuit are arranged parallel to one another.
  • When two or more bulbs are connected separately to the same terminals of a dry cell, they are connected in parallel.
  • Electricity can flow through more than one path.

In the parallel circuit:
(a) If any of the bulbs is removed, the remaining bulbs still light up.
(b) A broken connection in one path does not affect the connection in other paths.

  • When one of the bulb is removed or fuses, the other paths in the circuit is not broken.
  • The other one bulb still light up because electricity can flow through the other paths.

  • The brightness of bulbs in a parallel circuit is not affected by the number of bulbs.

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