Question

In regions of low humidity, one develops a special “grip” when opening car doors, or touching metal door knobs. This involves placing as much of the hand on the device as possible, not just the ends of one’s fingers. Discuss the induced charge and explain why this is done.

Short answer

In low humidity regions, if one uses the grip that involves placing as much of the hand on the doorknob, the induced charges provide attractive forces for a better grip. And if one touches it with a finger, they may receive a shock.

Step-by-step solution

Charging by induction

When a charged conductor is placed very close to an uncharged object without touching, the nearer end of the uncharged body acquires a charge opposite on the charged conductor and the two bodies attract each other. The charge developed on the uncharged body is known as the Induced charge.

Low humidity

In regions of low humidity, the air has very high resistance and the charges do not discharge easily.

When we bring out hands close to the metal knobs, the static charges on the knobs induce charges of the opposite kind, on the hand. If we grip the knob by placing as much of the hand on the device as possible, the charges are induced all over the hand.

Therefore, in the low humidity regions, if one uses a grip that involves placing much of the hand on doorknobs, the attractive forces due to induced charges provide a better grip. While touching it with a finger, may produce a shock on the finger.