Electronics

A light dependent resistor

A light dependent resistor can resist the flow of electricity through it

Set up the circuit

:

Lamp distance from LDR What happens to the light bulb, how bright is it?

5cm 10cm What is your conclusion about how the LDR works??

Light Dependent resistor

• The amount of resistance it has depends on how much light is shining on the resistor.

• The more light is shining on the LDR the more current it lets flow through it

Application of an LDR • LDRs are used as controls of street lamps

Electrical switches

• A Switch can be used to complete or break a circuit

A diode

• A diode allows electrical current to flow in

one direction only

.

Investigating a diode in a circuit

Which of these circuits will the bulb light up in?

What way should the diode be facing for electricity to flow?

Diode

• When connected to a power supply it will only allow electricity to flow if it is forward facing

Applications of a diode in a circuit •Diodes are used to change alternating current current in a circuit to direct In an a.c power supply the electricity is constantly changing direction of flow!

The diode will only allow the electricity to flow when it flowing in one particular direction!

LED

• An LED is a diode that emits light current passed through them.

as Symbol

LEDS

• LED’s are often used as power indicators on radios, TV’s and other electronic devices.

• LED’s are used instead of bulbs as they need less current to work!!