Resistors Lamps and Diodes

A resistor is an electrical componant that restricts the flow of electric current. 

the current flowing through a resistor at a constant temperature is directly proportional to the potential difference across it-----Ohms Law

 Heats up when electric current passes through

lamp resistance increases as the temperature increases. Current flowing is not directly proportional to the voltage accross it. 

A diode has a very high resistance in one direstion, meaning current only ever flows in the other direction. Good for warning lights etc

Light emitting Diodes (LEDS) produce light when a current flows through them in a forward direction

Often used as indicator lights. Use much smaller current, increased use 

Thermistors are used as temperature sensors, eg fire alarms. The resistance decreases as the temperature increases

LDRs are used to detect light levels, eg auto security lights. The resistance decreaes as the light intensity increases.