science

electric current can cause a magnectic field which is how a electromagnet works. 

electric can cause the ability to heat thing and can cause chemical reactions.

The magnetic field around an electromagnet is just the same as the one around a bar magnet. It can, however, be reversed by turning the battery around. Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off just by closing or opening the switch.

Relays are electrically operated switches. They use an electromagnet, often to control a high-power circuit using a low-power signal or where multiple circuits need to be controlled by one circuit.

A wave of compression and rarefaction, by which sound is propagated in an elastic medium such as air.

Longitudinal waves

Sound waves are longitudinal waves - the vibrations are in the same direction as the direction of travel. We can detect sound using our ears. An ear has an eardrum inside, connected to three small bones. The vibrations in the air make the eardrum vibrate, and these vibrations are passed through the three small bones (called ossicles) to a spiral structure called the cochlea. Signals are passed from the cochlea to the brain through the auditory nerve, and our brain interprets these signals as sound.

• the amplitude is the maximum height of the wave from its resting position – the greater the amplitude, the louder the sound
• the wavelength is the distance between the crests (tops) of two waves next to each other (or any other two identical point on waves next to each other)
• the frequency is the number of waves per second – the higher the frequency, the closer together the waves are and the higher the pitch