Question: Q. 9. In the given figure, charge +Q is placed at the centre of a dotted circle. Work done in taking another charge fq from A to B is W1 and from B to C is W2. Which one of the following is correct?

(i) W1>W2

(ii) W1=W2

(iii) W1<W2

U] [CBSE SQP 2017-18]

Show Answer

Solution:

Ans. (ii)

As VAVB=VBVC magnitude of work done is same.

[CBSE Marking Scheme 2017] 1

Detailed Answer :

As we know E=dVdr and inside a ring there is zero electric field which means constant potential

VAVB=VBVC

Magnitude of work done is same.

1

Answering Tip

  • Points A and B are at same potential lies on a equipotential surface.

[I] Q. 10. What is the amount of work done in moving a point charge around a circular arc of radius r at the center where another point charge is located? A&E [O.D. Comptt. I, II, III 2014]

Ans. Let q1 be the charge inside the circle and q2 be the charge moving around the circular arc, then work done

W=14πε0q1q2r2

The work done in moving the charge over the circular arc is zero, because it is moving over an equipotential surface.



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