JEE Main 26-Aug-2021 Shift 2 Solved Paper

Given, charges on two rings are +Q and -Q, respectively as shown below. Potential at centre of ring A due to charge on ring A and charge onring B is given as
VA=

kQ

a

−

kQ

√s2+a2

Similarly, potential at centre of ring B due to charge on ring B and charge on ring A is given as
VB=−

kQ

a

+

kQ

√s2+a2

Potential difference between centre of both the rings is
ΔV=VA−VB
=

2kQ

a

−

2kQ

√s2+a2

=

Q

2πε0

(

1

a

−

1

√s2+a2

) (∵k=

1

4πε0

Nm2C−2)
Thus, potential difference between centre of both the rings is

Q

2πε0

[

1

a

−

1

√s2+a2

]