Name: Electric and Gravitational Forces
Uploaded: 2019-07-19
Duration: 3 min 11 s
Description: Do you know the difference and similarities between the gravitational force and electrostatic force? Watch this video to explore it. Don't miss it.

Question

Two plane sheets of charge densities $+ σ$ and $- σ$ are kept in air as shown in Fig. 1.161. What are the electric field intensities at points $A$ and $B$ ?

Accepted Answer

Let us consider the point B in between the given plane sheets. The net electric field intensity in this region would be the sum of the electric field intensities due to both the given plane sheets, but we have to take the direction of these fields into account. We know that the electric fields are directed from positive to negative. So, the electric field intensity on B due to the left plane sheet would be directed away from the plate, and it would be directed towards the right plate with the same magnitude. (also the same direction)
Net electric field intensity at A would be,

$E_{A} = \frac{σ}{2 ε_{0}} + \frac{σ}{2 ε_{0}} = \frac{2 σ}{2 ε_{0}} ∴ E_{A} = \frac{σ}{ε_{0}}$

Hence, net electric field intensity at point A is found to be $E_{A} = \frac{σ}{ε_{0}}$

Very similarly at point A, the electric field due to the left plate would be directed away from the plate, and it would be directed towards the right plate (i.e, in opposite directions) with equal magnitudes.
Net electric field intensity at point A would be,

$E_{B} = \frac{σ}{2 ε_{0}} - \frac{σ}{2 ε_{0}} ∴ E_{B} = 0$

Hence, net electric field intensity at point B is found to be zero.

Two plane sheets of charge densities $+ σ$ and $- σ$ are kept in air as shown in Fig. 1.161. What are the electric field intensities at points $A$ and $B$ ?

Important Questions on Electric Charges and Field

Learn and Prepare for any exam you want !

Two plane sheets of charge densities +σ and -σ are kept in air as shown in Fig. 1.161. What are the electric field intensities at points A and B?

Important Questions on Electric Charges and Field

Learn and Prepare for any exam you want !

Two plane sheets of charge densities $+ σ$ and $- σ$ are kept in air as shown in Fig. 1.161. What are the electric field intensities at points $A$ and $B$ ?