The Voltage of a Cell.The ability of a cell to drive a current is measured

by its voltage.

The volt symbol “V”.

When cells are arranged in series with the positive

terminal of one cell connected to the negative

terminal of the next cell, it can be calculated by

adding their voltages.

The potential difference or voltage between two

points in a circuit is measured by a voltmeter.

The voltmeter is connected into a circuit with its positive terminal connected to a wire that leads towards the positive terminal of the cell.

Measuring Voltage.

In an ammeter, the wires are attached to either side of the part of the circuit being tested.

It is arranged in parallel with this part of the circuit.

Measuring Voltage.

Ohm’s Law

Resistance The material through which a current flows offers

some resistance to the moving electrons.

High resistance

Low resistance

Small current with an

applied voltage

Large current with the

same voltage

an

d

The wires connecting the components in a

circuit have a low resistance while wires in

filaments of the lamps has high resistance.

When they connect in series their resistance

combine the same way as the voltages of

the cells in series – They add.

LAMPS AND CURRENT SIZE

The size of the current flowing can be

estimated by looking at the brightness of the

lamps.

The lamp will shine brighter with more power

and it will shine less when there is less power.

The lamp also shares it’s power with other

components in the circuit.

The ammeter reading varies in the following way. At points A and D the

readings are the same. At points B and C, if the lamps are identical the

readings will be the same and exactly half the readings at A and D. so if A

and D are 6.0 amps the readings at B and C will be 3.0 amps.

A D

B

C

The total of the readings of the ammeters at B and C is

always the same as the reading at A and D even if the

bulbs are not identical. For example: if the reading at A and

D is 5.0 amps and the reading at B is 3.0 amps then the

reading at C will be 2.0 amps.

LIGHT-DEPENDENT

RESISTOR

A light-dependent resistor (LDR) is made from 2 piece of

metal which are jointed together by a semiconductor.

Semiconductor is a material that has just a few

electrons which can move freely. When the LDR receives

light energy, more electrons are released in the

semiconductor, and the resistance of the LDR becomes

lower. When the amount of light shining on it reduced,

fewer electrons are released and the resistance

increases.

This is the

symbol for

LDR

Normal Bright

Dim

• Current can flow only in one direction.

• Used to control the direction of the flow of

a current through complicated circuits

(components in series and parallel).

• Have a band marked at one end.

• The symbol should be drawn with the

straight line facing the negative terminal of

the source of the current.

LED

• An LED is a semiconductor diode,

allowing a current to flow in only one

direction and it produces light.

• It can emit red, yellow and green light.

• In electronic circuits an LED performs the

same task more efficiently.

PRESENTED BY :

MASON

TASYA

PAWITRA

WILL

Thank you for listening and

paying attention