Question

What is the value of work required to move a + 8 nC charge from infinity to a point P which is at 2 m distance from a point charge Q= +5 μC?

1. 180 μJ
2. 180 nJ
3. 18 μJ
4. 18 nJ

Answer 1

Correct Answer - Option 1 : 180 μJ

Concept:

Work done in bringing a charge from infinity to a point is

W = Q₁ × V

\(V = \frac{1}{{4\pi \in }}\frac{{{Q_2}}}{r}\)

Q₁ and Q₂ are the two charges.

r: distance

Calculation:

Given charges are 8 nC and 5 μC respectively.

Distance (r): 2 m

\(\;W = \frac{1}{{4\pi \in }}\frac{{{Q_1}{Q_2}}}{r}\)

\(W = 9 \times {10^9}\frac{{8 \times {{10}^{ - 9}} \times 5 \times {{10}^{ - 6}}}}{2}\)

W = 180 μJ