A choke is preferred to resistance for limiting current in AC circuit because

• choke is cheap

• there is no wastage of power

• choke is compact in size

• choke is a good absorber of heat

A current of 6 A enters one comer P of an equilateral triangle PQR having 3 wires of resistances 2Q each and leaves by the corner R. Then the current I₁ and I₂ are

• 2 A, 4 A

• 4 A, 2 A

• 1 A, 2 A

• 2 A, 3 A

All components of the electromagnetic spectrum in vacuum have the same

• energy

• velocity

• wavelength

• frequency

In the Wheatstone's network given, P = 10Ω, Q = 20Ω, R =15Ω, S = 30Ω, the current passing through the battery (of negligible internal resistance) is

• 0.36 A

• zero

• 0.18 A

• 0.72 A

A proton and a deuteron with the same initial kinetic energy enters a magnetic field in a direction perpendicular to the direction of the field. The ratio of the radii of the circular trajectories described by them is

• 1 : 4

• 1 : √2

• 1 : 1

• 1 : 2

Two identical capacitors each of capacitance 5 µF are charged to potentials 2 kV and 1 kV respectively. Their -ve ends are connected together. When the +ve ends are also connected together, the loss of energy of the system is

• 160 J

• Zero

• 5 J

• 1.25 J

An inductance of $\left(\frac{200}{\mathrm{\pi }}\right)\mathrm{mH}$, a capacitance of $\left(\frac{{10}^{-3}}{\mathrm{\pi }}\right)\mathrm{F}$ and a resistance of 10Ω are connected in series with an AC source 220 V, 50 Hz. The phase angle of the circuit is

• $\frac{\mathrm{\pi }}{6}$

• $\frac{\mathrm{\pi }}{4}$

• $\frac{\mathrm{\pi }}{2}$

• $\frac{\mathrm{\pi }}{3}$

A step-down transformer reduces the voltage of a transmission line from 2200 V to 220 V. The power delivered by it is 880 W and its efficiency is 88%. The input current is

• 4.65 mA

• 0.045 A

• 0.45 A

• 4.65 A

39.

A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is

• 1.2 cm

• 1.2 mm

• 2.4 cm

• 2.4 mm

When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is sufficient for liberating photoelectrons. The ratio of the work function of the two emitters is

• 1 : 2

• 2 : 1

• 4: 1

• 1: 4