Question

In figure are shown charges q₁ = + 2 × 10^–8C and q₂ = – 0.4 × 10^–8C. A charge q₃ = 0.2 × 10^–8C in moved along the arc of a circle from C to D. The potential energy of q₃

• A. Will increase approximately by 76%
• B. Will decreases approximately by 76%
• C. Will remain same
• D. Will increases approximately by 12%

Answer 1

Answer: (B)

Will decreases approximately by 76%

Answer 2

Initial potential energy of q_3­ $U_{i} = \left( \frac{q_{1}q_{3}}{0.8} + \frac{q_{2}q_{3}}{1} \right) \times 9 \times 10^{9}$

Final potential energy of q₃ $U_{f} = \left( \frac{q_{1}q_{3}}{0.8} + \frac{q_{2}q_{3}}{0.2} \right) \times 9 \times 10^{9}$

Change in potential energy = U_f – U_i

Now percentage change in potential energy $= \frac{U_{f} - U_{i}}{u_{i}} \times 100$

$= \frac{q_{2}q_{3}\left( \frac{1}{0.2} - 1 \right) \times 100}{q_{3}\left( \frac{q_{1}}{0.8} + \frac{q_{2}}{1} \right)}$ On putting the values $\widetilde{–} - 76\%$