# Five positive charges of magnitude q are arranged symmetrically around the circumference of a circle of radius r. What is the magnitude of the electric field at the center of the circle?

1. Zero
2. $$\mathrm{\frac{kq}{r^{2}}}$$
3. $$\mathrm{\frac{5kq}{r^{2}}}$$
4. $$\mathrm{\frac{kq}{r^{2}}cos\left[ \frac{2\pi}{5} \right]}$$
5. $$\mathrm{\frac{5kq}{r^{2}}cos\left[ \frac{2\pi}{5} \right]}$$

Correct Option: ()

# A charge Q is placed at the center of the line joining two equal charges Q. The system of three charges will be in equilibrium if q is equal to

1. -Q/2
2. -Q/4
3. Q/4
4. Q/2

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# A particle moves with a constant speed of v in a magnetic field B. The work done is

1. Zero
2. Proportional to the velocity
3. Proportional to the magnetic field
4. Proportional to the charge q of the particle

Correct Option: ()

A particle moves with a constant speed of v in a magnetic field B. The work done is zero.

# Two charges are placed on the x-axis. The positive charge is +8q at the origin and the negative charge is -2q at x = L. At which point on the x-axis is the net electric field due to these two charges zero?

1. x = 0
2. x = L
3. x = -L
4. x = 2L
5. x = -L/2

Correct Option: ()

# If the electric flux through a closed surface S is equal to zero, then

1. The volume charge density is zero everywhere inside the surface S
2. The electric field at every point on S is zero
3. The electric field is zero at every point inside S
4. The net charge enclosed by S is zero

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# A charge Q is placed upon a capacitor C at a potential difference V. The potential energy stored in the capacitor may be determined from which one of the following expressions?

1. PE = QV2/2
2. PE = CV/2
3. PE = VC2/2
4. PE = Q2/2C

Correct Option: ()

# In an electric dipole, the electric field intensity is directly proportional to

1. $$\mathrm{\frac{1}{r}}$$
2. $$\mathrm{\frac{1}{r^2}}$$
3. $$\mathrm{\frac{1}{r^3}}$$
4. $$\mathrm{\frac{1}{r^4}}$$

Correct Option: ()

The relationship between the electric field intensity and the distance from the dipole is given by

$\mathrm{E \propto \frac{1}{r^{3}}}$

This means that the electric field intensity is directly proportional to the inverse cube of the distance from the dipole.

# The ends of a 5 m long uniform conducting wire are connected to 10 volts battery. The strength of the electric field at every point within the wire is

1. Zero
2. Varying
3. 2 V/m
4. From -ve to the +ve terminal

Correct Option: ()

# If two adjacent parallel conductors free to move are placed within 2 cm of each other, and a 25 A direct current is sent through each in the same direction, the tendency of the conductors will be to

1. Move apart
2. Come together
3. Remain stationary
4. Move at a right angle to each other

Correct Option: ()

The direction of the force can be determined using the right-hand rule. If the current in both conductors is flowing in the same direction then the force will be attractive and the conductors will tend to come together.

1. $\boldsymbol{\overrightarrow{\mathrm{S}}&space;=&space;\frac{\overrightarrow{\mathrm{E}}}{\overrightarrow{\mathrm{H}}}}$
2. $\boldsymbol{\overrightarrow{\mathrm{S}}&space;=&space;\frac{\overrightarrow{\mathrm{E}}}{\overrightarrow{\mathrm{B}}}}$
3. $\boldsymbol{\overrightarrow{\mathrm{S}}&space;=&space;\overrightarrow{\mathrm{E}}&space;\times&space;\overrightarrow{\mathrm{B}}}$
4. $\boldsymbol{\overrightarrow{\mathrm{S}}&space;=&space;\overrightarrow{\mathrm{E}}&space;\times&space;\overrightarrow{\mathrm{H}}}$