Q138 / 180 · KCET 2025 · Physics

A potential at a point A is -3 V and that at another point B is 5 V . What is the work done in carrying a charge of 5 m C from B to A ?

  • Correct answer
    A
    -0.04 J
  • B
    -0.4 J
  • C
    -4 J
  • D
    -40 J

Solution

$\begin{aligned} & \text { Wext }=q \Delta V \\ & =q\left(V_f-V_i\right) \\ & =5 \times 10^{-3}\left(V_A-V_B\right) \\ & =5 \times 10^{-3}(-3-5) \\ & =-8 \times 5 \times 10^{-3} \mathrm{~J} \\ & =-40 \times 10^{-3} \mathrm{~J} \\ & =-0.04 \mathrm{~J}\end{aligned}$

Hence, the correct answer is option: 'A'.

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