Question

Two small conductors carrying charges 10 and 20 nano coulomb respectively are separated 0.3
apart in air .find the electric field at a point midway between them.
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Answer 1

Given info : Two small conductors carrying charges 10 and 20 nC respectively are seperated 0.3 m apart in air .

To find : the electric field at a point midway between them is ...

solution : 10nC -------------O-------------20nC

here O is the midpoint of the line joining the two charges.

electric field due to 10nC at point O, E₁ = kq/r² = (9 × 10⁹ × 10 × 10⁻⁹)/(0.15)² = 90/0.0225 = 4000 N/C along east.

electric field due to 20 nC at point O, E₂ = (9 × 10⁹ × 20 × 10⁻⁹)/(0.15)²

= 180/0.0225 = 8000 N/C along west.

so, the net electric field at point O = E₁ + E₂

           = 4000 ( east) + 8000 ( west) = -4000 (west) + 8000(west)

           = 4000 (west)

therefore the net electric at a point midway between them is 4000 N along west.