Question

A particle of mass 'm' having charge 'q' is held at rest in uniform electric field of intensity 'E'. When it is released, the kinetic energy attained by it after covering a distance 'y' will be ______.

Options

• `"mE"/"q"`y

• Eqy

• `"mqy"/"E"`

• mEqy

Answer 1

A particle of mass 'm' having charge 'q' is held at rest in uniform electric field of intensity 'E'. When it is released, the kinetic energy attained by it after covering a distance 'y' will be Eqy.

Explanation:

F = qE    ∴ a = `"qE"/"m"`

a = `"dV"/"dt" = "dV"/"ds" * "ds"/"dt" = "V" "dV"/"ds"`

`therefore "VdV" = "qE"/"m"`ds

`"V"^2/2 = "qE"/"m"`y

`therefore "V"^2 = "qE"/"m"`y

`"E" = 1/2 "mV"^2 = 1/2 "m" "qE"/"m"`y = qEy