﻿ Medical Entrance Exam Question and Answers | Electric Charges and Fields - Zigya

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# Electric Charges and Fields

#### Multiple Choice Questions

91.

An infinite sheet carrying a uniform surface charge density σ lies on the xy-plane. The work done to carry a charge q from the point  to the point  (where a is a constant with the dimension of length and ε0 is the permittivity of free space) is

• $\frac{3\mathrm{\sigma aq}}{2{\mathrm{\epsilon }}_{0}}$

• $\frac{2\mathrm{\sigma aq}}{{\mathrm{\epsilon }}_{0}}$

• $\frac{5\mathrm{\sigma aq}}{2{\mathrm{\epsilon }}_{0}}$

• $\frac{3\mathrm{\sigma aq}}{{\mathrm{\epsilon }}_{0}}$

92.

Consider two concentric spherical metal shells of radii r1 and r2 (r2 > r1). If the outer shell has a charge q and the inner one is grounded, the charge on the inner shell is

• zero

• - q

93.

The line AA' is on charged infinite conducting plane which is perpendicular to the plane of the of the paper. The plane has a surface density of charge σ and B is ball of mass m with a like charge of magnitude q. B is connected by string from a point on the line AA'. The tangent of angle (θ) formed between the line AA' and the string is • $\frac{\mathrm{q\sigma }}{2{\mathrm{\epsilon }}_{0}\mathrm{mg}}$

• $\frac{\mathrm{q\sigma }}{4{\mathrm{\pi \epsilon }}_{0}\mathrm{mg}}$

• $\frac{\mathrm{q\sigma }}{2{\mathrm{\pi \epsilon }}_{0}\mathrm{mg}}$

• $\frac{\mathrm{q\sigma }}{{\mathrm{\epsilon }}_{0}\mathrm{mg}}$

94.

A hollow sphere of external radius R and thickness (t << R) is made of a metal of density ρ. The sphere will float in water, if

95.

A charge q is placed at one corner of a cube. The electric flux through any of the three faces adjacent to the charge is zero. The flux through any one of the other three faces is

• q/3ε0

• q/6ε0

• q/12ε0

• q/24ε0

96.

Two charges + q and -q are placed at a distance a in a uniform electric field. The dipole moment of the combination is , where, θ is the angle between the direction of the field and the line joining the two charges. Which of the following statement(s) is/are correct ?

• The torque exerted by the field on the dipole vanishes

• The net force on the dipole vanishes

• The torque is independent of the choice of coordinates

• The net force is independent of a