Electrostatics – Two kinds of Charges
Introduction:
If a glass rod is rubbed with silk cloth it acquires a positive charge, while silk cloth acquires an equal amount of negative charge.
If an ebonite rod is rubbed with fur, it acquires a negative charge, while the fur acquires a positive charge.
This classification was done by the American scientist Benjamin Franklin.
Thus charging a rod by rubbing does not create electricity, but the charges are simply redistributed.
Like charges are repelled and unlike charges are attracted. This property has many applications such as powder coating, electrostatic paint sprayer etc.
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Positive Charge
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Negative charge
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Glass rod
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Silk cloth
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Fur
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Ebonite rod
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Woolen cloth
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Plastic pen
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Woolen carpet
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Rubber shoes
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The above table explains substances which acquire positive and negative charges on rubbing.
MCQS based on the above concept:
1. When we rub the glass rod with the silk, the silk acquires
A) positive charge b) negative charge c) both the charges
d) No charge
b) is the correct answer, because whenever a glass rod is rubbed with silk, the silk attains a negative charge.
2. The force between like charges is
a) Attraction b) repulsion c) No force
The correct answer is b)
The force exhibited by the like charges is force of repulsion. Only unlike charges attract each other.