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| Numerical 01 |
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| 01. Two identical balls, each of mass 0.1 x 10-3 kg, carry identical charges and are suspended by two threads of equal length. At equilibrium, they position themselves as shown in the figure below. Calculate the charge on either ball. |
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| Suggested answer: |
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| The ball on the left is in equilibrium under the action of following three forces: |
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| (i) Tension T in the thread |
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| (ii) Weight mg of the ball |
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| (iii) Coulomb repulsion, F |
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| Tension T can be resolved into two rectangular components - |
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| T cos 60o and T sin 60o. |
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| For equilibrium, F = T cos 60o, mg = T sin 60o |
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| Dividing, |
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| Substituting, we get |
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| or q =10-7 C = 0.1 mC |
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Electric Charges and Field
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