```CIRCUIT Diagrams and Symbols
 Electrical circuits can be represented by circuit diagrams
 The various electrical components are shown by using standard symbols in
circuit diagrams
 Components can be connected in series or in parallel.
The diagram below shows the standard circuit symbols you need to know.
CIRCUIT DIAGRAMS
Two things are important for a circuit to work:


There must be a complete circuit
There must be no short circuits
To check for a complete circuit, follow a wire coming out of the battery with your finger. You
should be able to go out of the battery, through the lamp, and back to the battery.
To check for a short circuit, see if you can find a way past the lamp without going through any
other component. If you can, there is a short circuit and the lamp will not light.
Look at the book page 62. You have diagrams of a normal circuit :
1. using a cell
2. using a battery
Now work out the exercises below.
. Exercises.
a. In the table below draw the circuit symbols to show a bulb, a cell (battery), a switch and a
wire.
a bulb
a cell (battery)
a switch
a wire
b. Use symbols to draw a circuit diagram of the following in the adjacent box.
c. Circuit 2 is incomplete. Paula tries to light up the bulb by completing the circuit using
different objects. She uses:
a plastic ruler an iron nail a rubber a metal spoon an aluminium foil
Circuit 2
Complete the table by putting each of the above objects in the correct column.
. Column A:
The bulb lights up with
Column B:
The bulb does not light up with
Objects in column A are called __________________________.
Objects in column B are called __________________________
SERIES AND PARALLEL CIRCUITS
 Components that are connected one after another on the same loop of the
circuit are connected in series.
 The current that flows across each component connected in series is the
same.
 The circuit diagram shows a circuit with three lamps connected in series. If
one lamp breaks, the other lamp will not light.
 In a series circuit , bulbs have to share the electrical force (called voltage)
between them, so they do not light up very brightly.
 Components that are connected on separate loops are connected in
parallel.
 The current is shared between each component connected in parallel.
 The circuit diagram shows a circuit with two lamps connected in parallel. If
one lamp breaks, the other lamp will still light.
 In a parallel circuit, the bulbs do not have to split up the voltage so the
bulbs light up brightly. Each bulb is switched on and off without affecting
each other.
Exercises.
1.Which of the circuits below are connected in series, and which in parallel?
_____________________________
__________________
_________________________________
________________________
2a.Emily is setting up an electrical circuit. She has wires, switches,
bulbs and cells(batteries). She does not use them all.
Draw the symbols of the following:
Components
bulb
Symbols
Cell (battery)
switch
b. Look at the picture of Emily’s circuit
Use the symbols to draw a diagram of Emily’s circuit.
c. The bulbs in Emily’s circuit are very bright. Emily removes one
cell (battery) from the circuit. Complete the sentence below to
describe the effect on the bulbs of removing a cell.
The bulbs will be __________________________________________
d. Complete this sentence:
The circuit above has the bulbs connected in _____________________.
e. What happens to the other bulb if one bulb is removed?
f. Look again at Emily’s circuit. In what other way could the bulbs be
connected? Draw this circuit.
The bulbs in this circuit are connected in ________________________
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