21.

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

What is the electric potential at a distance of 9 cm from 3 nC ?

• 270 V

• 3 V

• 300 V

• 30 V

A voltmeter reads 4 V when connected to a parallel plate capacitor with air as a dielectric. When a dielectric slab is introduced between plates for the same configuration, voltmeter reads 2 V. What is the dielectric constant of the material ?

• 0.5

• 2

• 8

• 10

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

A carbon film resistor has colour code Green, Black, Violet, Gold. The value of the resistor is

• 50 MΩ

• 500 MΩ

• 500 ± 5% MΩ

• 500 ± 10% MΩ

Two resistors of resistances 2 Ω and 6 Ω are connected in parallel. This combination is then connected to a battery of emf 2 V and internal resistance 0.5 Ω. What is the current flowing through the battery ?

• 4 A

• $\frac{4}{3} \mathrm{A}$

• $\frac{4}{17} \mathrm{A}$

• 1 A

The equivalent resistance of two resistors connected in series is 6 Ω and their parallel equivalent resistance is  $\frac{4}{3} \mathrm{\Omega }$. What are the values of resistances ?

• 4 Ω, 6 Ω

• 8 Ω, 1 Ω

• 4 Ω, 2 Ω

• 6 Ω, 2 Ω

In a potentiometer experiment of a cell of emf 1.25 V gives balancing length of 30 cm. If the cell is replaced by another cell, balancing length of 30 cm. If the cell is replaced by another cell, balancing length is found to be 40 cm. What is the emf of second cell ?

• ≈ 1.57 V

• ≈ 1.67 V

• ≈ 1.47 V

• ≈ 1.37 V