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Three point charges 10μC, 20μC and 30μC are separated by some distance located at three points. Whole system is in equilibrium. Charges 10μC, 20μC and 30μC exert a force of 30N on 30μC and 20N on 20μC. So, force exerted on point charge 10μC will be:

Three point charges 10μC, 20μC and 30μC are separated by some distance located at three points. Whole system is in equilibrium. Charges 10μC, 20μC and 30μC exert a force of 30N on 30μC and 20N on 20μC. So, force exerted on point charge 10μC will be: Correct Answer -50 N

CONCEPT:

Superposition Principle: 

  • The principle of superposition states that when a number of charges are interacting, the total force on a given charge is the vector sum of the forces exerted on it due to all other charges.
  • The force between two charges is not affected by the presence of other charges.
  • This is used to calculate the following parameter at the observation point, to any configuration of charges.
    • Net force.
    • Net electric field.

 

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CALCULATION:

If system is in equilibrium, then total force on all charges will be zero.

F1 + F2 + F3 = 0

∴ F1 = -(F2 + F3)

Force on 10μC charge will be -

F1 = -(30 + 20) = -50N

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