Magnet are usually made of iron and (a)  

Iron thumbtack is ... materials.

(a)  

The ... of a magnet are the parts where the magnetic attraction is the strongest.

(a)  

Two S-Pole are called ... pole.

(a)  

Look at the picture! Part B is (a)  

The bulb lights up because the metal filament in the bulb become (a)  

The more bulb connected one after another, the bulb will be (a)  

A switch is used to open or close an (a)  

Look at this picture! This is an (a)   circuit.

Sound are made when things or air (a)  

The volume of a sound is measure in units called (a)  

Noise barriers keep the ... from rumbling trains.

(a)  

High or low a sound is called (a)  

The longest panpipe makes the sound with the ... pitch.

(a)