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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Electric Field and Potential

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Field and Potential

An electric field given by E = i Ax is present in a region of...

An electric field given by E⃗=i⃗Ax\vec{E} = \vec{i} Ax is present in a region of space, where A=10 V m−2A = 10 \text{ V m}^{-2}. If the potential at (10 m,20 m)(10 \text{ m}, 20 \text{ m}) is assumed to be zero, calculate the potential at the origin.

Options

  1. A1000 V1000 \text{ V}
  2. B−500 V-500 \text{ V}
  3. C−1000 V-1000 \text{ V}
  4. D500 V500 \text{ V}

Correct answer

D. 500 V500 \text{ V}

Step-by-step solution

The relation between electric field and potential is given by dV=−E⃗⋅dr⃗dV = -\vec{E} \cdot d\vec{r}.

Given E⃗=Axi^\vec{E} = A x \hat{i}, we have:

dV=−(Axi^)⋅(dxi^+dyj^+dzk^)=−AxdxdV = -(A x \hat{i}) \cdot (dx \hat{i} + dy \hat{j} + dz \hat{k}) = -A x dx

Integrating both sides from the reference point (10,20)(10, 20) to the origin (0,0)(0, 0):

∫V(10,20)V(0,0)dV=−∫100Axdx\int_{V(10, 20)}^{V(0, 0)} dV = -\int_{10}^{0} A x dx

V(0,0)−V(10,20)=−A[x22]100V(0, 0) - V(10, 20) = -A \left[ \dfrac{x^2}{2} \right]_{10}^{0}

Substituting V(10,20)=0V(10, 20) = 0 and A=10 V m−2A = 10 \text{ V m}^{-2}:

V(0, 0) - 0 = -10 \left( 0 -\dfrac{10^2}{2} \right)

V(0,0)=−10(−50)=500 VV(0, 0) = -10 (-50) = 500 \text{ V}
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