Q.A flat, square surface with sides of length L is described by the equations x = L, 0 ≤ y ≥ L, 0 ≤ z ≥ L. The electric flux through the square due to a positive point charge q located at the origin (x = 0, y = 0, z = 0) is

(a) q/4ε_{o}

(b) q/6ε_{o}

(c) q/24ε_{o}

(d) q/48ε_{o}

Ans: C

# Author: Rajesh Jha

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## A spherical shell of radius R = 1.5cm has a charge q = 20μC uniformly distributed over it. The force exerted by one half over the other half is

Q.A spherical shell of radius R = 1.5cm has a charge q = 20μC uniformly distributed over it. The force exerted by one half over the other half is

(a) zero

(b) 10^{-2} N

(c) 500 N

(d) 2000 N

Sol: E= σ/2ℇ_{0} , Pressure P = σ^{2}/2ℇ_{0}

Force F = P × πR^{2}

= σ^{2}/2ℇ_{0} × πR^{2}

= (q /4 πR^{2} )^{2} πR^{2}/2ℇ_{0}

Putting the given value

Ans: D

## In a region of space, the electric field is given by E ⃗=8i ̂+4j ̂+3k ̂. The electric flux through a surface of area 100 units in the xy plane is

## Consider two concentric spherical surfaces, S1 with radius a and S2 with radius 2a, both centered at the origin. There is a charge +q at the origin and there are no other charges. Compare the flux 1 through S1 with the flux 2 through S2

Q.Consider two concentric spherical surfaces, S1 with radius a and S2 with radius 2a, both centered at the origin. There is a charge +q at the origin and there are no other charges. Compare the flux φ_{1} through S1 with the flux φ_{2} through S2.

(a) φ_{1} = 4φ_{2}

(b) φ_{1} = 2φ_{2}

(c) φ_{1} = φ_{2}

(d) φ_{1} = φ_{2} /2

Ans: C