LEDs (Light Emitting Diodes)
Leds are much like bulbs, but do not need a holder. They use less power, and the are less bright. There may well be an LED on you computer to show that it is turned on! LEDs can only be connected one way around.
Bulbs
Here is a red and a clear bulb. Bulbs can be connected to the +ve and -ve either way around. The brightness of a bulb is rated in Watts. Different bulbs use different voltages.
Buzzers
Here are two types of buzzer. There is probably a buzzer in your alarm clock if it is battery powered! Buzzers usually can only be connected one way around. The red wire should be connected to the +ve, and the black to the -ve.
Moving Coil Meter
This is a picture of a moving coil meter. You may have seen things like this in Hi-fi's. They are used to show the amount of power passing through them. They use electromagnetism.
Motors
These use electromagnetism to make them go around. If you connect a motor the wrong way around it will spin backwards!
