Test Index

NCERT Class XII Chapter
Electrostatic Potential and Capacitance
Questions With Solutions

© examsnet.com
Question : 36
Total: 37
A small sphere of radius r1 and charge q1 is enclosed by a spherical shell of radius r2 and charge q2. Show that if q1 is positive, charge will necessary flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge q2 on the shell is.
Solution:  
The potential on inner small sphere is
VA = VAA+VAB
or VA =
1
4πε0
[
q1
r1
+
q2
r2
]
whereas the potential on the outer shell B is

VB = VBA+VBB =
1
4πε0
[
q1
r1
+
q2
r2
]
So, VA−VB =
1
4πε0
[
q1
r1
−
q1
r2
] =
q1
4πε0
[
r2−r1
r1r2
]
As r2 > r1, so VA > VB i.e. inner sphere A is at higher potential than outer conducting shell B, for any value of charge q1. So, when inner sphere A is connected to outer shell B, then charge will flow from inner sphere A to outer shell B, until electric potentials on them is same i.e.
VA−VB = 0 or q1 = 0 [As r1 ≠ r2]
So, charge q1 given to sphere A will flow on the shell B, no matter what the charge on the shell B is.
© examsnet.com
Go to Question:
Prev Question
Next Question