When a given coil is connected to a 200V, 50 Hz AC source, 1 A current flows in the circuit. The inductive reactance of the coil used is

• $50\sqrt{3} \mathrm{\Omega }$

• $200\sqrt{3} \mathrm{\Omega }$

• $150\sqrt{3} \mathrm{\Omega }$

• $100 \sqrt{3} \mathrm{\Omega }$

When a given coil of ohmic resistance 100 Ω and inductive reactance 100$\sqrt{3}$ Ω is connected to a 200 V DC source, the current flows in the circuit is

• 1 A

• 1.5 A

• 2 A

• $100\sqrt{3}$ Ω

Two point charges + q and + 4q are located at x = O and x = L respectively. The location of a point on the x-axis at which the net electric field due to these two points charges is zero, is

• L / 3

• 2 L

• 4 L

• 8 L

If electric flux entering and leaving an enclosed surface is ${\mathrm{\varphi }}_1$ and ${\mathrm{\varphi }}_2$ respectively, the electric charge inside the enclosed surface will be

• $\left({\mathrm{\varphi }}_1 + {\mathrm{\varphi }}_2\right) {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_2 - {\mathrm{\varphi }}_1\right) {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_1 + {\mathrm{\varphi }}_2\right) / {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_2 - {\mathrm{\varphi }}_1\right) / {\mathrm{\epsilon }}_0$

In a potentiometer experiment, the balancing with a cell is at 240 cm. On shunting the cell with a resistance of 2 Ω the balancing length becomes 120 cm. The internal resistance of the cell is

• 0.5 Ω 

• 1 Ω 

• 2 Ω 

• 4 Ω 

The total current supplied to the circuit by the battery is

• 1 A

• 2 A

• 4 A

• 5 A

A place where the vertical component of the earth's magnetic field is zero has angle of dip is

• 45°

• 90°

• 0°

• 60°

A tank is filled with water to a height of 12.4 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.3 cm. If water is replaced by a liquid of refractive index 1.6 upto the same height, by what distance would the microscope have to be moved to focus on the needle again

• 4 cm

• 3 cm

• 2.18 cm

• 1.55 cm

A ray of light falls on a transparent right-angled isosceles prism made from a glass of refractive index $\sqrt{2}$. The incident ray falls normally on one of the equal sides of this prism. The ray will suffer

• total internal reflection

• Interference

• refraction with angle of refraction 90°

• None of the above

50.

The magnifying power of a telescope in its normal adjustment is 20. If the length of the telescope is 105 cm in this adjustment, the focal length of the objective lens is

• 100 cm

• 5 cm

• 80 cm

• 95 cm