A rheostat has 2 contacts and is usually used to control current. Uses include controlling lamp brightness or motor speed and changing the rate of flow of charge into a capacitor in a timing circuit.
Aerial (Antenna) A device to receive or transmit radio signals. It is also known as an antenna.
Ammeter Measures current.
Transistor PNP A transistor amplifies current and can be used with other components to make an amplifier or switching circuit. This symbol is for a bipolar junction transistor (BJT), the type you are most likely to use at first.