H-Bridge

In an H Bridge you can control the direction of motors from clockwise to anticlockwise. The connections of the H bridge are shown below.

H-Bridge                          

we have used four transistors to construct the H bridge. The 4 transistors and the load are arranged in the shape of H. Hence it is referred to as H- bridge.

case 1: When A and A' are High ( B and B' are Low)

when a current is supplied to the base of transistor A and A'. the two transistors start to conduct. Here no current is supplied to the base of transistor B and B'. Hence current flows from A to A'. .which makes the transistor rotate in clockwise direction.

case 2: When B and B' are High (A and A' are Low)

when a current is supplied to the base of transistor B and B'. The two transistors start to conduct.here no current is supplied to the base of transistor A and A'. Hence current flows from B to B'. which makes the transistor rotate in anti-clockwise direction.

Note: For practical use, you can use IC L293D to control the motor. It has the H bridge circuit and is compact.