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Class 12
Physics
Electric Charges and Field
two large thin metal plates are parallel and clos...

Question:
Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17.0 × 10⁻²² C/m². What is E:

(a) in the outer region of the first plate,

(b) in the outer region of the second plate, and

(c) between the plates?

Answer:

The situation is represented in the following figure.

A and B are two parallel plates close to each other. Outer region of plate A is labelled as I, outer region of plate B is labelled as III, and the region between the plates, A and B, is labelled as II.

Charge density of plate A, σ = 17.0 × 10⁻²² C/m²

Charge density of plate B, σ = −17.0 × 10⁻²² C/m²

In the regions, I and III, electric field E is zero. This is because charge is not enclosed by the respective plates.

Electric field E in region II is given by the relation,

Where,

∈0 = Permittivity of free space = 8.854 × 10⁻¹² N⁻¹C² m⁻²

∴

= 1.92 × 10⁻¹⁰ N/C

Therefore, electric field between the plates is 1.92 × 10⁻¹⁰N/C.

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