Q1. Work done in moving a test charge between two points in an electric field is independent of the path followed. Comment.
Ans : The work done in moving a test charge between two points in an electric field is independent of path i.e. the work done depends only on the location of initial and final positions of the charge. In fact, it is true for all the fields oveying inverse square law.
Q2. A positive charge +q is located at a point. What is the work done, if a unit positive charge is carried once around this charge along a circle of radius r about this point ?
Ans : The potential at each point on the circular path around the charge is same i.e. potential difference between the initial and final position is zero.
Therefore, work done, W = V × q = 0 × 1 = 0
Q3. Why the electric field is always at right angles to the equipotential surface ? Give reason.
Ans : The work done in moving a test charge between two points on an equipotential surface can be zero, only if electric field is at right angles to the equipotential surface.
Q4. What do you mean by potential energy of an electric dipole, when placed in electric field ?
Ans : An electric dipole always tends to orient itself along the direction of electric field. Work has to be done in rotating the dipole to some other orientation and this work done in rotating the dipole gets stored in the dipole in the form of its potential energy.
Q5. A charge of 2 C moves between two plates maintained at a potential difference of 1 volt. What is the energy acquired by the charge ?
Ans : Energy gained by charge,
W = V . q = 1 × 2 = 2 J
Q6. What is the dimensional formula of potential gradient?
Ans : [M L T −3 A−1]
Q7. Name the physical quantity,whose SI unit is volt metre −1
Ans : Electric field intensity
Q8.What is an equipotential surface ?
Ans : Any surface, which has same electrostatic potential everywhere, is called an equipotential surface.
Q9. What is the shape of equipotential surfaces for a given point charge ?
Ans : For a point charge, the equipotential surfaces are concentric spherical shells, whose centres are located at the given point charge.
Q10. The electric potential is constant in a region. What can you say about electric field there ?
Ans : We know, E = − dV/dr
Since V is constant, electric field is zero.
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