Electrostatic Force

Electrically charged objects exert force on an uncharged object or a charged object is called electrostatic force. For example, a plastic comb or plastic pen which is electrically charged by rubbing in dry hair, exerts an electrostatic force on uncharged tiny pieces of paper and attracts them.

The electric charges are of two types: positive electric charges and negative electric charges. Electric charges can be produced by friction when one object is rubbed over another object. The term 'electrostatic' refers to 'stationary electric charges'. An object having stationary electric charges (or static electric charges) on it is called electrically charged object. A comb acquires electrostatic charge after it has been rubbed with dry hair. An electrically charged object exerts an electrostatic force. It is called electrostatic force because the electric charges involved in it remain static (or stationary). The electric charges remain confined to the charged object and do not move.

Activity: To show that electrically charged by rubbing in dry hair, exerts an electrostatic force on uncharged tiny pieces of paper

1. Take a plastic comb (or plastic pen) and rub it in dry hair for about one minute.

2. Bring this comb near the tiny pieces of paper.

Observation: The comb attracts the tiny pieces of paper. The tiny pieces of paper move towards the comb and stick to it.

Explanation: When the plastic comb is rubbed in dry hair, the comb gets electric charges by friction. And when this electrically charged comb is brought near the tiny pieces of paper, it exerts an electrostatic force of attraction on them. Due to this electrostatic force, the tiny pieces of paper move towards the comb and stick to it.

Some more example of electrostatic force are

1 The electrostatic force is responsible for raising our body hair when we try to take off a terylene or polyester shirt in dry weather.

2. An inflated balloon when rubbed with a piece of synthetic cloth and then pressed against a wall, the balloon sticks to the wall. It is the electrostatic force which is responsible for the attraction between the balloon and the wall.

As the electrostatic force can be exerted by a charged object on another object from a distance, so it is an example of a non-contact force. Just like magnetic force, an electrostatic force can be of attraction or repulsion depending on the situation. The electrostatic force between any charged object (positively charged object or negatively charged object) and an uncharged object is always of attraction. The electrostatic force between two charged objects having like charges is that of repulsion. On the other hand, the electrostatic force between two charged objects having unlike charges is of attraction.

Sample Questions

(More Questions for each concept available in Login)

Question : 1

Photocopy works on the principle of __________
A. Magnetism	B. Electrostatic	C. Mechanical	D. Friction
Right Option : B
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Question : 2

__________________ is not a contact force.
A. Muscular force	B. Electrostatic force	C. Frictional force	D. None of the above
Right Option : B
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Question : 3

Which of the following are correct ? (a) The electric charges are of two types: positive electric charges and negative electric charges. (b) An object having stationary electric charges on it is called electrically charged object. (c) The electrostatic force is responsible for raising our body hair when we try to take off a polyester shirt in dry weather.
A. Only (a) and (b) is correct .	B. Only (b) and (c) is correct .	C. Only (a) and (c) is correct .	D. All of these .
Right Option : D
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