Question

5. A point charge q, is held stationary at the origin. A second charge q2 is placed at a point a, and
the electric potential energy of the pair of charges is -6.4 x 10-8 J. When the second charge is
moved to point b, the electric force on the charge does 4.2 x 10- 8Jof work. What is the electric
potential energy of the pair of charges when the second charge is at point b?​

Answer 1

Solution :-

Given that :-

Charge (q) is at origin

Charge (q1) is at point A {initially}

Electric potential Energy = -6.4 × 10⁻⁸

Now

Charge (q1) is moved to point B

Work done = 4.2 × 10⁻⁸

Now as question ask for the Electric potential Energy when charge (q1) is at Point B.

We have got

$\rightarrow W_{el} = - \triangle U$

$\rightarrow 4.2 \times 10^{-8} = U_A - U_B$

$\rightarrow U_B = U_A - 4.2 \times 10^{-8}$

$\rightarrow U_B = -6.4 \times 10^{-8} - 4.2 \times 10^{-8}$

$\rightarrow U_B = -10.6 \times 10^{-8}$

$\rightarrow U_B = -1.06 \times 10^{-7}$