1. Starter: use Pg 206-211 to complete the table
LO: Describe the action of thermistors and light- dependent resistors and show understanding
of their use as input transducers
LDR’s and Thermistors
Component
Circuit symbol
Diode
Light Dependent Resistor
Starter: use Pg to complete the table
Variable Resistor
Thermistor
Can you think of any electrical devices which turn on without a switch?

2. Light dependant resistor – resistance DECREASES when light intensity INCREASES
Street lamps use LDR’s so they know when to switch on and off
Digital cameras use LDR’s to control the amount of light which is allowed in
Resistance
Amount of light

3. Thermistor – resistance DECREASES when temperature INCREASES
Used in central heating timers

4. Students need to look at the following pictures and write down what they have in common – that they all need electricity to work.
Which is the odd one out? 4