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Model 1 Mark Book Back Questions (New Syllabus) 2020

12th Standard EM

Reg.No. :
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Physics

Time : 00:20:00 Hrs
Total Marks : 20

Part A

20 x 1 = 20
1. A parallel plate capacitor stores a charge Q at a voltage V. Suppose the area of the parallel plate capacitor and the distance between the plates are each doubled then which is the quantity that will change?

(a)

Capacitance

(b)

Charge

(c)

Voltage

(d)

Energy density

2. The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is

(a)

0.2 Ω

(b)

0.5 Ω

(c)

0.8 Ω

(d)

1.0 Ω

3. Th ree wires of equal lengths are bent in the form of loops. One of the loops is circle, another is a semi-circle and the third one is a square. Th ey are placed in a uniform magnetic fi eld and same electric current is passed through them. Which of the following loop confi guration will experience greater torque ?

(a)

circle

(b)

semi-circle

(c)

square

(d)

all of them

4. A simple pendulum with charged bob is oscillating with time period T and let θ be the angular displacement. If the uniform magnetic field i switched ON in a direction perpendicular to the plane of oscillation then

(a)

time period will decrease but θ will remain constant

(b)

time period remain constant but θ will decrease

(c)

both T and θ will remain the same

(d)

both T and θ will decrease

5. In a transformer, the number of turns in the primary and the secondary are 410 and 1230 respectively. If the current in primary is 6A, then that in the secondary coil is

(a)

2 A

(b)

18 A

(c)

12 A

(d)

1 A

6. Which of the following electromagnetic radiation is used for viewing objects through fog

(a)

microwave

(b)

gamma rays

(c)

X- rays

(d)

infrared

7. Which of the following is NOT true for electromagnetic waves?

(a)

it transport energy

(b)

it transport momentum

(c)

it transport angular momentum

(d)

in vacuum, it travels with different speeds which depend on their frequency

8. An air bubble in glass slab of refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness of the slab is,

(a)

8 cm

(b)

10 cm

(c)

15 cm

(d)

20 cm

9. A ray of light strikes a glass plate at an angle 60o. If the reflected and refracted rays are perpendicular to each other, the refractive index of the glass is,

(a)

$\sqrt3$

(b)

$\frac{3}{2}$

(c)

$\sqrt{\frac{3}{2}}$

(d)

2

10. In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would

(a)

increase by 2 times

(b)

decrease by 2 times

(c)

decrease by 4 times

(d)

increase by 4 times

11. Two radiations with photon energies 0.9 eV and 3.3 eV respectively are falling on a metallic surface successively. If the work function of the metal is 0.6 eV, then the ratio of maximum speeds of emitted electrons will be

(a)

1:4

(b)

1:3

(c)

1:1

(d)

1:9

12. The ratio between the first three orbits of hydrogen atom is

(a)

1:2:3

(b)

2:4:6

(c)

1:4:9

(d)

1:3:5

13. In J.J Thomson e/m experiment, a beam of electron is replaced by that of muons (particle with same charge as that of electrons but mass 208 times that of electrons). No deflection condition is achieved only if

(a)

B is increased by 208 times

(b)

B is decreased by 208 times

(c)

B is increased by 14.4 times

(d)

B is decreased by 14.4 times

14. The nucleus is approximately spherical in shape. Then the surface area of nucleus having mass number A varies as

(a)

A2/3

(b)

A4/3

(c)

A1/3

(d)

A5/3

15. If a half –wave rectifi ed voltage is fed to a load resistor, which part of a cycle the load current will flow?

(a)

00–900

(b)

900–1800

(c)

00–1800

(d)

00–3600

16. Th e principle in which a solar cell operates

(a)

Diffusion

(b)

Recombination

(c)

Photovoltaic action

(d)

Carrier flow

17. If the input to the NOT gate is A = 1011, its output is

(a)

0100

(b)

1000

(c)

1100

(d)

0011

18. The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called _______.

(a)

Amplitude modulation

(b)

Frequency modulation

(c)

Phase modulation

(d)

Pulse width modulation

19. Which one of the following is the natural nanomaterial

(a)

Peacock feather

(b)

Peacock beak

(c)

Grain of sand

(d)

Skin of the Whale

20. The alloys used for muscle wires in Robots are

(a)

Shape memory alloys

(b)

Gold copper alloys

(c)

Gold silver alloys

(d)

Two dimensional alloys