Electric Circuits and symbols

S.MORRIS 2006

ELECTRICAL CIRCUITS

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The CELL

A battery stores chemical

energy

transfers it to electrical energy

when circuit is closed

When two or more cells are connected

together we call this a Battery.

Multiple Choice

What type of energy is stored in a battery?

• solar

• wind

• chemical

Multiple Choice

In order for electrical energy to flow, a circuit must be _____.

• open

• closed

simple circuits

Here is a simple electric circuit.

energy source

lamp

wires

switch

What is an electric current?

An electric current is electrons flowing through

wires

+ -

In which direction does the current flow?

Current flows from positive to negative

simple circuits

When the switch is closed, the lamp lights up.

Need a continuous path of metal for electric current

If there were any breaks in the circuit, the current
could not flow.

Multiple Choice

Will the light bulb be on in this circuit?

• Yes, the light bulb will be lit.

• No, the light bulb will not be lit.

Multiple Choice

How do you know if the light bulb will light up in this circuit?

• The battery is connected backwards.

• The light bulb is broken

• The switch is closed.

• A wire is not connected.

circuit diagrams

In circuit diagrams components are represented by
the following symbols;

cell

battery

switch

lamp

motor

ammeter

voltmeter

buzzer

resistor

variable
resistor

circuit diagram

battery

switch

lamp

wires

Scientists usually draw electric circuits using symbols;

Match

Match the following

battery

switch

resistor

lamp

wire

• battery

• switch

• resistor

• lamp

• wire

types of circuit

There are two types of electrical circuits;

SERIES CIRCUITS

PARALLEL CIRCUITS

The components are connected end-to-end, one
after the other.

SERIES CIRCUITS

If one bulb ‘blows’ it breaks the whole circuit and
all the bulbs go out.

PARALLEL CIRCUITS

The current has a choice of routes.

The components are connected side by side.

If one bulb ‘blows’ there is still be a complete circuit to
the other bulb so it stays alight.

measuring current

Electric current is measured in amps(A) using

a multimeter connected in series in the circuit.

A

measuring current

A

This is how we draw a multimeter for amps in a circuit.

SERIES CIRCUIT PARALLEL CIRCUIT

​A

measuring current

SERIES CIRCUIT

PARALLEL CIRCUIT

• current is the same
at all points in the
circuit.

2
A

2
A

2
A

• current is shared
between the
components

2
A

2
A

1
A
1
A

copy the following circuits and fill in the
missing ammeter readings.

?
A

?A

4
A

?
A
?

1
A

3
A

?
A

?
A

measuring voltage

The ‘electrical push’ which the cell gives to the current

is called the voltage. It is measured in volts (V) on a

multimeter

V

measuring voltage

V

This is how we draw a multimeter in a circuit to read voltage.

SERIES CIRCUIT

PARALLEL CIRCUIT

V

V

measuring voltage

V

V

V

series circuit

1.5
V

• voltage is shared between the components

1.5
V

3
V

• voltage is the same in all parts of the circuit.

3
V

parallel circuit

3
V

3
V

measuring current & voltage

copy the following circuits on the next two
slides.

complete the missing current and voltage
readings.

remember the rules for current and voltage
in series and parallel circuits.

practice problems measuring current & voltage

V

V

6
V

4
A

A

A

a)

measuring current & voltage

V

V

6
V

A

A

b)

4
A

A

answers

3
V

3
V

6V

4A
4
A

6
V

6
V

6V

4A

4
A

2
A

2
A

4
A

a)

b)

4A