Electrostatics Question 774

Question: The potential at the point x (measured inμm ) due to some charges situated on the x-axis is given by V(x)=20(x24) volt. The electric field E at x=4μm

Options:

A) (10/9)volt/μm and in the +ve x direction

B) (5/3)volt/μm and in the -ve x direction

C) (5/3)volt/μm and in the +ve x direction

D) (10/9)volt/μm and in the -ve x direction

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Answer:

Correct Answer: A

Solution:

[a] Here, V(x)=20x24volt

We know that E=dVdx=ddx(20x24)

or, E=+40x(x24)2

At x=4μm ,

E=+40×4(424)2=+160144=+109volt/μm .

Positive sign indicates that E is in +ve x-direction.



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