Question

A + 3.0 nC charge Q is initially at rest at a distance of r₁ = 10 cm from a +5.0 nC charge q fixed at the origin. The charge Q is moved away from q to a new position at r₂ = 15 cm. In this process work done by the field is ______.

विकल्प

• 1.29 × 10⁻⁵ J

• 3.6 × 10⁵ J

• −4.5 × 10⁻⁷ J

• 4.5 × 10⁻⁷ J

Answer 1

A + 3.0 nC charge Q is initially at rest at a distance of r₁ = 10 cm from a +5.0 nC charge q fixed at the origin. The charge Q is moved away from q to a new position at r₂ = 15 cm. In this process work done by the field is 4.5 × 10⁻⁷ J.

Explanation:

Work done = `int_(r_1)^(r_2) vecF vec(dr)`

= `int_(r_1)^(r_2) (kqQ)/r^2 dr`

= `kqQ [1/r_1 - 1/r_2]`

= (8.99 × 10⁹) × (5 × 10⁻⁹) × (3 × 10⁻⁹)[1/0.1 − 1/0.5]

= 4.5 × 10⁻⁷ J