What do you mean by short circuit ?

Explanation

1. Connect the circuit as shown in the figure.

2. Switch on the circuit. We see that the bulb glows.
3. Now connect a copper wire between C and D as shown in the figure.

Now switch on the circuit.
5. We observe that the bulb does not glow. The ammeter shows more reading than in the previous case.
6. Here the filament of bulb offers a very high resistance than the copper wire, between C and D. Therefore, current choses the path CD and avoids the path PQ. Hence the bulb does not glow.
7. This indicates that the current prefers a path of least resistance in the circuit.
8. This method of connecting wire in between C and D is known as 'short circuiting.