Final charge on capacitor is

where = charge on capacitor at
=time constant of the circuit.
Putting

Given,
Hence,

The electric field of a hollow spherical capacitor is localised in between inner and outer surface of the spherical conductor.
Therefore, at point , the electric field will not be zero.

(say)
This charge will remain constant after switch is shifted from position 1 to position 2.


Energy dissipated80% of the initial stored energy .

Consider the charge distribution as shown. Considering the branch on upper side, we have



Here,
…(i)
…(ii)
From Eqs. (i) and (ii), we get


Similarly for the lower side branch
…(iii)
...(iv)
From Eqs. (iii) and (iv)

Net emf in the circuit here
volt
While the equivalent capacity

Charge on each capacitor

Potential difference across capacitor

Since so electric field will point from plate 2 to plate 1.
The electron will experience an electric force, opposite to the direction of electric field, and hence move towards the plate 2.

Use work-energy theorem to find speed of electron when it strikes the plate 2.

Where is the required speed.

The circuit is given as

Let be the charge after switch has been closed.
Then,

…(i)
But we know that, charge is conserved

or …(ii)
On putting the value of Eq. (ii)



Now, from Eq. (i)


Hence,

applying principle of moments
F (0.6)=100(0.8)
ÞF=133.3N

Applying the condition of rotational equilibrium,

But