Question

Around a stationary charge of +5µC, another charge -5µC is taken once round a circle of radius 4 cm. The amount of work done in Joule is

• A. \(\frac{2\pi}{5}\)
• B. \(\frac{3\pi}{8}\)
• C. zero
• D. \(\frac{4\pi}{5}\)
• E. \(\frac{\pi}{4}\)

Answer 1

The Correct Option is C

The work done \( W \) in moving a charge in an electric field is given by: \[ W = q \cdot V \] where \( q \) is the charge being moved and \( V \) is the potential at the point where the charge is located. In this case, the charge is being moved in a circular path around a stationary charge.
Since the stationary charge is fixed, the electric potential around it is constant for any circular path around it.
Therefore, there is no change in potential as the charge moves around the circle. Since the electric potential remains constant, the work done in moving the charge is zero.

The correct option is (C) : zero

Answer 2

The work done in moving a charge in an electrostatic field depends only on the initial and final positions, because the electrostatic force is a conservative force.  

If the charge is moved around a closed path (like a circle), the initial and final positions are the same. 

Therefore, the net work done is: 
$$ W = 0 \, \text{Joule} $$ 
Answer: \( \boxed{0} \)