Question

A cubical iron block is given a charge of +40m C and placed in vacuum.

1. Give the direction of electric field at the centre of one face.

2. Calculate the net flux due to the charged cube through one face.

3. Will there be any change in the flux if it is placed underwater of dielectric constant 81. Justify.

Answer 1

1. Normally outwards from the surface.

Total flux = \(\frac{40\times10^{-3}}{8.85\times10^{-12}}\) = 4.51 x 10⁹Nm²C^-1

2. Through one face = \(\frac{4.51\times10^9}{6}\) = 0.75 x 10⁹Nm²C^-1

3. Electric flux decreases because flux depends on permittivity of medium.