1.

Two circular rings A and B each of radius a = 30 cm are placed coaxially with their axis horizontal in a uniform electric field E = 10^(5) NC^(-1)directed vertically upward as shown in figure. Distance between centers of the rings A and B (C_A and C_B)is 40 cm. Ring A has positive charge q_A = 10muCand B has a negative charge q_B = -20muC. A particle of mass m and charge q = 10muC is released from rest at the center of ring A. If particle moves along C_AC_B, then Work done by electric field, when particle moves from C_A to C_B is

Answer»

`-1.2 J`
1.2 J
`-3.6 J`
`3.6J`

SOLUTION :`W=q(V_(2)-V_(1))=9xx10^(-2)[((10)/(0.3)-(20)/(05))-((10)/(0.5)-(20)/(0.3))]`
`=3.6J`
Since only conservative forces act on the system, potential energy CHANGES to kinetic energy.
`3.6=(1)/(2)mv^(2)` or `V^(2)=72` or `v=6sqrt(2)ms^(-1)`


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