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#### 12th All Chapter 1 mark Impatant Question

12th Standard EM

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 44
44 x 1 = 44
1. The total electric fl ux for the following closed surface which is kept inside water

(a)

$\frac { 80q }{ { \varepsilon }_{ 0 } }$

(b)

$\frac { q }{ { 40\varepsilon }_{ 0 } }$

(c)

$\frac { q }{ { 80\varepsilon }_{ 0 } }$

(d)

$\frac { q }{ { 160\varepsilon }_{ 0 } }$

2. If voltage applied on a capacitor is increased from V to 2V, choose the correct conclusion

(a)

Q remains the same, C is doubled

(b)

Q is doubled, C doubled

(c)

C remains same, Q doubled

(d)

Both Q and C remain same

3. At Infinity (i.e r = ∞), the electrostatic potential (V) is

(a)

(b)

maximum

(c)

minimum

(d)

Zero

4. Electrostatics deals with the _________

(a)

charges in motion

(b)

static electric charges

(c)

charges through conductors

(d)

accelerated charges

5. Th e following graph shows current versus voltage values of some unknown conductor. What is the resistance of this conductor?

(a)

2 ohm

(b)

4 ohm

(c)

8 ohm

(d)

1 ohm

6. The temperature coefficient of resistance of a wire is 0.00125 per °C. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at

(a)

1154 K

(b)

1100 K

(c)

1400 K

(d)

1127 K

7. The resistance of the wire varies inversely as

(a)

area of cross section

(b)

resistivity

(c)

length

(d)

temperature

8. The transition temperature of mercury is________

(a)

4.2°C

(b)

4.2 K

(c)

2.4°C

(d)

2.4K

9. 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

10. A non-conducting charged ring of charge q, mass m and radius r is rotated with constant angular speed ω. Find the ratio of its magnetic moment with angular momentum is

(a)

$\\ \frac { q }{ m }$

(b)

$\\ \frac { 2q }{ m }$

(c)

$\\ \frac { q }{ 2m }$

(d)

$\\ \frac { q }{ 4m }$

11. Two parallel conductors of length 10m carrying same current separated by 20cm in air experiences a force of 0.9N. then the current in each conductor is

(a)

30A

(b)

300nA

(c)

300$\sqrt { 2 }$A

(d)

300A

12. The heating element that does not oxidize readily in an alloy of metals made of ______

(a)

Nickel and Iron

(b)

Nickel and Chromium

(c)

Copper and Magnanin

(d)

Nickel and Copper

13. In an electrical circuit, R, L, C and AC voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and current in the circuit is $\frac{\pi}{3}$. Instead, if C is removed from the circuit, the phase difference is again  $\frac{\pi}{3}$.  The power factor of the circuit is

(a)

1/2

(b)

1/$\sqrt2$

(c)

1

(d)

$\sqrt3$/2

14. In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is

(a)

$\frac{Q}{2}$

(b)

$\frac{Q}{\sqrt3}$

(c)

$\frac{Q}{\sqrt2}$

(d)

Q

15. Transformer works on

(a)

AC only

(b)

DC only

(c)

both AC and DC

(d)

AC more effectively than DC

16. In a LCR series a.c, circuit, the phase difference between current and voltage is 60°. If the net reactance of the circuit is 17.32Ω, the value of the resistance is

(a)

30Ω

(b)

17.32 Ω

(c)

10 Ω

(d)

1.732 Ω

17. A radiation of energy E falls normally on a perfectly refl ecting surface. Th e momentum transferred to the surface

(a)

$\frac{E}{c}$

(b)

2$\frac{E}{c}$

(c)

Ec

(d)

$\frac { E }{ { c }^{ 2 } }$

18. The electric and magnetic fields of an electromagnetic wave are

(a)

in phase and perpendicular to each other

(b)

out of phase and not perpendicular to each other

(c)

in phase and not perpendicular to each other

(d)

out of phase and perpendicular to each other

19. The wavelength of electromagnetic wave produced by Hertz experiment was

(a)

6mm

(b)

60m

(c)

6000 mm

(d)

60 cm

20. ______ radiations are used in destroying bacteria.

(a)

UV

(b)

IR

(c)

X-ray

(d)

Gamma rays

21. For light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is,

(a)

30o

(b)

45o

(c)

60o

(d)

90o

22. Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are

(a)

5I and I

(b)

5I and 3I

(c)

9I and I

(d)

9I and 3I

23. For the largest distance of the image from a concave mirror of focal length 10 cm, the object should be kept at

(a)

10 cm

(b)

Infinite

(c)

40 cm

(d)

60 cm

24. A short liner object of length I lies along the axis of a concave mirror of focal length f at a distance μ1from the pole of the mirror. The size of the image is approximately equal to

(a)

$1\left| \cfrac { u-f }{ f } \right| ^{ \frac { 1 }{ 2 } }$

(b)

$1\left| \cfrac { \mu -f }{ f } \right| ^{ 2 }$

(c)

$1\left| \cfrac { f }{ \mu -f } \right| ^{ \frac { 1 }{ 2 } }$

(d)

$1\left| \cfrac { f }{ \mu -f } \right| ^{ 2 }$

25. The wavelength λe of an electron and λp of a photon of same energy E are related by

(a)

λp $\alpha$ λe

(b)

${ \lambda }_{ p }\alpha \sqrt { { \lambda }_{ e } }$

(c)

${ \lambda }_{ p }\alpha \frac { 1 }{ \sqrt { { \lambda }_{ e } } }$

(d)

${ \lambda }_{ p }\alpha { \lambda }_{ e }^{ 2 }$

26. The mean wavelength of light from sun is taken to be 550 nm and its mean power is 3.8 × 1026W. The number of photons received by the human eye per second on the average from sunlight is of the order of

(a)

1045

(b)

1042

(c)

1054

(d)

1051

27. In an electron microscope, the doughnut shaped electromagnet is called as _______

(a)

accelerator

(b)

electron gun

(c)

projector

(d)

condenser magnetic lens

28. For a given photo sensitive surface the ratio of stopping potential for three different incident frequencies

(a)

1: 2 : 3

(b)

1: 4: 9

(c)

1: 1 : 1

(d)

$\sqrt { 1 } :\sqrt { 2 } :\sqrt { 3 }$

29. 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

30. the nuclear radius of 27 al is 3.6 fermi, the approximate nuclear radius of 64Cu is

(a)

24

(b)

1.2

(c)

4.8

(d)

3.6

31. If R is Rydberg's constant, the muumum wavelength of hydrogen spectrum is

(a)

1/R

(b)

R/4

(c)

4/R

(d)

R

32. A good _____ slows down neutrons by elastic collisions and it does not remove them by absorption.

(a)

fuel

(b)

moderator

(c)

coolant

(d)

control rod

33. The barrier potential of a silicon diode is approximately

(a)

0.7 V

(b)

0.3V

(c)

2.0 V

(d)

2.2V

34. 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

35. Zener diode is used as _______

(a)

full wave rectifier

(b)

Amplifier

(c)

A.C. voltage regulator

(d)

D.C. voltage regulator

36. In PNP transistors, the direction of conventional current, when emitter-base junction is forward-biased is from __________

(a)

base to emitter

(b)

emitter to base

(c)

collector to base

(d)

base to collector

37. The output transducer of the communication system converts the radio signal into ________.

(a)

Sound

(b)

Mechanical energy

(c)

Kinetic energy

(d)

None of the above

38. The frequency range of 3 MHz to 30 MHz is used for

(a)

Ground wave propagation

(b)

Space wave propagation

(c)

Sky wave propagation

(d)

Satellite communication

39. The component of the modulated wave, which has a greater frequency than that of the carrier is called __________.

(a)

upper side band

(b)

middle side band

(c)

lower side band

(d)

stoke's band

40. The electron gun assembly contains a _________.

(a)

CRO

(b)

cathode and a control grid

(c)

multimeter

(d)

power supply

41. “Sky wax” is an application of nano product in the field of

(a)

Medicine

(b)

Textile

(c)

Sports

(d)

Automotive industry

42. The technology used for stopping the brain from processing pain is

(a)

Precision medicine

(b)

Wireless brain sensor

(c)

Virtual reality

(d)

43. Best example for applications. of nano technology

(a)

Chemical industry

(b)

Engineering

(c)

medicine

(d)

all of these

44. Plasma etching and chemical vapour deposition are synthesized by ____________

(a)

Bottom - up approach

(b)

Top - down approach

(c)

Bottom - down approach

(d)

Top - up approach