Q.

Two charges q1 and q2 are separated by a distance of 30 cm. A third charge q3 initially at 'C' as shown in the figure, is moved along the circular path of radius 40 cm from C to D. If the difference in potential energy due to movement of q3 from C to D is given by q3K4πε0, the value of K is:          [2025]

1 8q2  
2 6q2  
3 8q1  
4 6q1  

Ans.

(1)

Potential at CVC=kq10.4+kq20.5

Potential at DVD=kq10.4+kq20.1

The difference in potential energy,

U=(VDVC)(q3)=(kq20.1kq20.5)(q3)

U=8kq2q3=8q2q34πε0