81.

In the uniform electric field of E = 1 x 10⁴ NC^-1, an electron is accelerated from rest. The velocity of the electron when it has travelled a distance of 2 × 10^-2 m is nearly $\left(\frac{\mathrm{e}}{\mathrm{m}} \mathrm{of} \mathrm{electron} = 1.8 \times {10}^{-11} \mathrm{C} {\mathrm{kg}}^{-1}\right)$

• 8.5 × 10⁶ ms^-1

• 1.6 × 10⁶ ms^-1 

• 0.85 × 10⁶ ms^-1

• 0.425 × 10⁶ ms^-1

Acceleration of a charged particle of charge q and mass m moving in a uniform electric field of strength E is

• $\frac{\mathrm{q}}{\mathrm{mE}}$

• $\frac{\mathrm{qE}}{\mathrm{m}}$

• $\frac{\mathrm{m}}{\mathrm{qE}}$

• mqE

A small oil drop ofmass 10^-6 kg is hanging in at rest between two plates separated by 1 mm having a potential difference of 500 V. The charge on the drop is (g = 10 ms^-2)

• 2 × 10^-9 C

• 2 × 10^-11 C

• 2 × 10^-6 C

• 2 × 10^-9 C

A uniform electric field in the plane of the paper as shown. Here A, B, C and D are the ponits on the circle. V₁, V₂, V₃ and V₄ are the potentials at those points respectively. Then

• V_A = V_C, V_B = V_D

• V_A = V_C, V_B > V_D

• V_A > V_C, V_B > V_D

• V_A = V_B, V_C > V_D

Two metal spheres of radii 0.01 m and 0.02 m are given a charge of 15 mC and 45 mC respectively. They are then connected by a wire. The final charge on the first sphere is

• 40 × 10^-3 C

• 30 × 10^-3 C

• 20 × 10^-3 C

• 10 × 10^-3 C

If a charge on the body is 1 nC, then how many electrons are present on the body ?

• 1.6 × 10¹⁹

• 6.25 × 10⁹

• 6.25 × 10²⁷

• 6.25 × 10²⁸

Two equal and opposite charges of masses m₁ and m₂ are accelerated in an uniform electric field through the same distance. What is the ratio of their accelerations if their ratio of masses is $\frac{{\mathrm{m}}_1}{{\mathrm{m}}_2}$ = 0.5 ?

• $\frac{{\mathrm{a}}_1}{{\mathrm{a}}_2} = 0.5$

• $\frac{{\mathrm{a}}_1}{{\mathrm{a}}_2} = 1$

• $\frac{{\mathrm{a}}_1}{{\mathrm{a}}_2} = 2$

• $\frac{{\mathrm{a}}_1}{{\mathrm{a}}_2} = 3$

What is the nature of Gaussian surface involved in Gauss's law of electrostatic ?

• Scalar

• Electrical

• Magnetic

• Vector

A spherical conductor of radius 2 cm is uniformly charged with 3 nC. What is the electric field at a distance of 3 cm from the centre of the sphere ?

• 3 × 10⁶ Vm^-1

• 3 Vm^-1

• 3 × 10⁴ Vm^-1

• 3 × 10^-4 Vm^-1

The angle between the dipole moment and electric field at any point on the equatorial plane is

• 180°

• 0°

• 45°

• 90°