1) A flat square sheet of charge of side 50 cm carries a uniform surface charge density. An electron 0.5 cm from a point near the centre of the sheet experiences a force of 1.8 X 10 - 12 N, directed away from the sheet. Determine the total cahrge on the sheet.
2) Two identical small equally spaced charge conducting balls are suspended from long threads secured at one point. The charges and masses of the balls are such that they are in equilibrium when the distance between them is a (the length of thread L >> a ). One of the balls is then discharged. What will be the distance b (b <<L) between the balls when equlibrium is restored ?
11)
Since it is a sheet of charge, by Gauss' Law, electric field is σ2ε
Given F = 1.8 x 10-12 N, q = 1.6 x 10-19 we get electric field = Fq = 1.125 x 107 N/C
Equate this,
σ2ε = 1.125 x 107
We get σ = 9.95 x 10-4
So charge on sheet = Q = σA = 2.4875 x 10-4 C
