Electrostatic Potential and Capacitance - Online Test
Q1. For a one dimensional electric field the correct relation of and potential V is
Answer : Option B
Explaination / Solution:
Electric field is defined as the negative gradient of the potential. The potential decreases in the direction of the electric field.
Q2. Electric-field magnitude E at points inside and outside a positively charged spherical conductor having charge Q and a radius R are
Answer : Option B
Explaination / Solution:
Electric field inside a spherical conductor is zero since all the charge resides on the surface of the conductor and there is no charge in the interior of the conductor. For all external points, the conductor behaves as though its entire charge is concentrated at its center.
Q3.
If R is the radius of a spherical conductor, the dielectric strength, maximum electric-field magnitude to which it can be raised is
Answer : Option A
Explaination / Solution:
Dielectric strength is the maximum electric field intensity the medium can bear without suffering a breakdown. The electric field intensity has a maximum value on the surface of the spherical conductor, therefore,
Q4. The electric dipole potential falls off, at large distance r
Answer : Option D
Explaination / Solution:
The potential due to a dipole at a point (r ,θ)from its center is therefore,
Q5. An equipotential surface is a surface
Answer : Option D
Explaination / Solution:
When the potential at all points on the surface is the same; such a surface is called an equipotential surface. The potential difference between any two points on an equipotential surface is zero, while the potential may be positive, negative or even zero.
Q6. Which of the following is true about equipotential lines
Answer : Option B
Explaination / Solution:
The potential at all points on an equipotential surface is constant and work done in moving a charge on an equipotential surface is zero. Electric field lines show the direction of the electric field at the point. If the electric field lines were tangential, parallel or opposite to the equipotential surface, a tangential field will exist on the surface and work done in moving a charge on the surface is not zero. Therefore electric field lines are always perpendicular to the equipotential surface.
Q7. At the surface of a charged conductor, electrostatic field must be
Answer : Option A
Explaination / Solution:
Under static conditions, no current exists on the surface of a conductor. If the electric field at its surface is tangential or parallel to the surface, the tangential electric field would cause the charges to move on the surface of the conductor causing currents to flow on its surface. Therefore electrostatic field is always normal to the surface of a charged conductor at every point.
Q8. Electrostatic shielding is based
Answer : Option B
Explaination / Solution:
Electric field inside a cavity is always zero. The potential inside a cavity of a conductor is constant. The potential difference between any two points inside a charged conductor is zero. This phenomenon is called electrostatic shielding.
Q9. Capacitance is defined as
Answer : Option A
Explaination / Solution:
Capacitance of any conductor is defined as the ratio of the charge given to the conductor to the potential developed in conductor.C=Q/V
Q10. Correct formula for capacitance in terms of area A and distance d,of a parallel plate capacitor in vacuum is
Answer : Option D
Explaination / Solution:
The capacitance of a parallel plate capacitor is given by
