2. Electric Circuits
• Closed Circuit
Electric current flows through it.
• Open Circuit
There is a break.
Electric current does not flow through it.
3. Electric Circuits
• Circuit diagrams record the components
and connections of a circuit in a simple
and clear way.
• Basic Circuit symbols:
battery
bulb
2 batteries
switch
wire
4. Components of an
Electric Circuit
• Actual circuit versus Circuit diagram
battery
wire
battery holder
switch
bulb
wire
battery
switch bulb
5. In a circuit, the brightness of a bulb
depends on:
a) The number of batteries used
(the greater the number of batteries,
the brighter the bulb).
b) Arrangement of components of the
circuit.
6. Factors that affect the
brightness of a bulb:
1. The number of batteries (in series)
Single battery Multiple batteries
dimmer brighter
7. More ……
• As more batteries are added in series,
more current is available and the bulbs
become brighter.
• When too many batteries are added, the
current is so great that one of the bulbs
may blow/fuse (too much heat is made by
the filament that it burns out).
8. Factors that affect the
brightness of a bulb:
2. The arrangement of batteries
Batteries arranged Batteries arranged
in parallel in series
dimmer brighter
9. More ……
• Batteries need to be connected with the poles
in the proper direction for current to flow –
positive end of one battery needs to be joined
to the negative end of another.
• When the number of components is the same,
the bulb of the circuit with batteries arranged in
series is brighter than that in parallel.
• However, if one battery is removed, only the
bulb of the circuit with batteries arranged in
parallel remains lighted up.
10. Factors that affect the
brightness of a bulb:
3. The number of bulbs
Single bulb Multiple bulbs
brighter
dimmer
11. More ……
• The greater the number of bulbs, the
dimmer they are.
12. Factors that affect the
brightness of a bulb:
4. The arrangement of bulbs
Bulbs arranged Bulbs arranged
in Parallel in Series
brighter dimmer
13. Bulbs in series vs
Bulbs in parallel
Points for Arrangement of bulbs in:
comparison Series Parallel
Number of Only one path; 2 or more paths;
paths for the current passes through current splits up and
electric current components one after another passes through each branch
at the same time;
paths are independent
of each other
Brightness
Dimmer Brighter
of bulbs
If one bulb is Electric current cannot flow Electric current can still flow
removed or through the circuit, the through the other path and the
damaged remaining bulb will not light up other bulb still lights up
Application - Used in the connection of
circuits in the houses; twinkling
lights, bumper cars in fun fairs
14. Application ……
• All the lights in our houses were
connected in series, then we have to turn
on all the lights at the same time. If one
bulb blows, then all the bulbs will not light
up. Hence household lighting and wiring
is arranged in parallel. Each bulb has an
individual switch to control it.
• Christmas Tree lightings
