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JEE Physics Solved Question Paper 2014

Multiple Choice Questions

41.
A step down transformer has 50 turns on secondary and 1000 turns on primary winding. If a transformer is connected to 220 V, 1 A AC source, what is output current of the transformer ?

$\frac{1}{20} A$

20 A

100 A

2 A

20 A

We know that,

Power in the secondary coil = Power in the pnmary coil

$V_{S} \times N_{P} = V_{P} \times N_{S} or \frac{N_{S}}{N_{P}} = \frac{V_{S}}{V_{P}}$

(voltage aacross secondary coil = VS)

(voltage across primary coil = VP)

(NP = Number of turns in primary coil)]

(NS = Number of turns in secondary coil)

where NS = 50 turn, NP = 1000 turn

VP = 220 V, VS = ?

^{$\frac{50}{100} = \frac{V_{S}}{220} V_{S} = \frac{50 \times 220}{1000} V_{S} = 11 V But, V_{S} I_{S} = V_{P} I_{P} 11 \times V_{S} = 220 \times 1 I_{S} = \frac{220}{11} I_{S} = 20 A$}

42.

The average power dissipated in AC circuit is 2 W. If a current flowing through a circuit is 2 A impedance is 1 Ω, what is the power factor of the AC circuit ?

0.5
1
Zero
$\frac{1}{\sqrt{2}}$

43.

A plane electromagnetic wave of frequency 20 MHz travels through a space along x-direction. If the electric field vector at a certain point in space is 6 Vm^-1, what is the magnetic field vector at that point ?

2 × 10^-3 T
2 × 10^-8 T
2 T
$\frac{1}{2} T$

44.

Two capacitors of 10 pF and 20 pF are connected to 200 V and 100 V sources respectively. If they are connected by the wire, what is the common potential of the capacitors ?

133.3 V
150 V
300 V
400 V

45.

An object is placed at 20 cm in front of a concave mirror produces three times magnified real image. What is the focal length of the concave mirror ?

15 cm
6.6 cm
10 cm
7.5 cm

46.

A focal length of a lens is 10 cm. What is power of a lens in dioptre ?

0.1 D
10 D
15 D
1 D

47.

A microscope is having objective of focal length 1 cm and eyepiece of focal length 6 cm. If tube length is 30 cm and image is formed at the least distance of distinct vision, what is the magnification produced by the microscope. Take D = 25cm.

48.

A fringe width of a certain interference pattern is β = 0.002 cm. What is the distance of 5th dark fringe from centre ?

1 × 10^-2 cm
11 × 10^-2 cm
9 × 10^-3 cm
3.28 × 10⁶ cm

49.

Diameter of the objective of a telescope is 200 cm. What is the resolving power of a telescope ? Take wavelength of light = $5000 \overset{\circ}{A}$ .

6.56 × 10⁶
3.28 × 10⁵
1 × 10⁶
3.28 × 10⁶

50.

A polarized light of intensity I₀ is passed through another polarizer whose pass axis makes an angle of 60° with the pass axis of the former. What is the intensity of emergent polarized light from second polarizer ?