SS3: Physics - 2nd Term Examination

1. Question

What causes the Earth’s magnetic field?

The movement of liquid iron in the Earth’s outer core
The gravitational field of the Earth
The permanent magnet in the Earth’s core
All of the above

2. Question

The maximum angle of inclination of a layer of a rock with the horizontal is _________

Dip
Heave angle
Strike
Depth

3. Question

Which of the following is used to determine the direction of magnetic field in a current carrying conductor?

Left-hand thumb rule
Right-hand thumb rule
Right-hand palm rule
Left-hand palm rule

4. Question

According to Flemming’s left-hand rule, the index finger denotes?

Direction of magnetic field
Direction of current
Direction of force
Direction of force as well as current

5. Question

According to Flemming’s left-hand rule, the middle finger denotes?

Direction of magnetic field
Direction of current
Direction of force
Direction of force as well as current

6. Question

The relation between the direction of force and the direction of magnetic field is _________

Same direction
Opposite direction
Perpendicular
Unrelated

7. Question

Magnetic field is strong when____________

magnetic field lines are closer
magnetic field lines are farther
magnetic field lines are longer
magnetic field lines are thicker

8. Question

The force existing between two infinite parallel conductors is inversely proportional to ________

Radius of the conductors
Current in one of the conductors
The product of the current in the two conductors
The distance between the two conductors

9. Question

The angle of dip at equator is

0°
45°
60°
90°

10. Question

The force per unit length existing between two infinite parallel conductors is given by ___________

\( \frac{\mu_0i_1i_2}{2 \pi d} \)
\( \frac{\mu_0i_1i_2}{2 d} \)
\( \frac{\mu_0i_1}{2 \pi di_2} \)
\( \frac{\mu_0i_1i_2}{d} \)

11. Question

Which among the following, is the correct expression for force in a current carrying conductor if magnetic field is perpendicular to it?

F = Bi
F = B²il
F = Bil
F = Bl²

12. Question

When the current in a current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?

Increases
Decreases
Remains the same
Becomes zero

13. Question

If the intensity of the magnetic field is 100T, the length of the conductor is 10m and the magnitude of force perpendicular to the magnetic field is 10kN,calculate the current in the conductor.

100 A
100 mA
10 A
10 Ma

14. Question

If the intensity of the magnetic field perpendicular to current carrying conductor is 100T, the length of the conductor is 3m and the current in the conductor is 10A, calculate the magnitude of force perpendicular to the electric field.

300N
30N
30KN
3KN

15. Question

An E.M.F. can be induced by _________

Change in the magnetic field only
Change in the area of cross section only
Change in angle between magnetic field and area only
Change in the magnetic field, area or angle between them

16. Question

What happens to the current in a coil while accelerating a magnet inside it?

Increases
Decreases
Remains constant
Reverses

17. Question

The total number of magnetic field lines passing through an area is termed as

Voltage
EMF
Magnetic flux
Magnetic flux density

18. Question

What is emf?

Force
Voltage
Current
Flux

19. Question

According to Faraday’s laws of electromagnetic induction, an emf is induced in a conductor whenever ______________.

The conductor is perpendicular to the magnetic field
Lies in the magnetic field
Cuts magnetic lines of flux
Moves parallel to the magnetic field

20. Question

Direction of induced emf is determined by __________

Fleming’s left hand rule
Fleming’s right hand rule
Faraday’s law
Lenz’s law

21. Question

“The direction of an induced e.m.f. is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that e.m.f.”, this is the statement for?

Fleming’s left-hand rule
Fleming’s right-hand rule
Faraday’s law
Lenz’s law

22. Question

Which, among the following, is the formula for induced emf?

e = \( \frac{d \Phi }{dt} \)
e = \( \frac{dt}{d \Phi } \)
e =\( \scriptsize t \: \times \: \phi \)
e = \( \scriptsize t^2 \: \times \: \phi \)

23. Question

North pole induces __________

Clockwise current
Anti-clockwise current
Zero current
Infinite current

24. Question

What is the principle of the transformer?

Gauss law
Coulomb’s law
Electromagnetic induction
Ampere’s law

25. Question

Voltage induced in secondary coil of transformer is given by

\( \frac{N_p \: \times \: V_p}{N_s} \)
\( \frac{N_s \: \times \: V_p}{N_p} \)
\( \frac{N_p }{V_p} \scriptsize \: \times \: N_s \)
\( \frac{N_p}{V_p \: \times \: N_s} \)

26. Question

Function of a transformer is to __________

Convert AC to DC
Convert DC to AC
Step down or up the DC voltages and currents
Step down or up the AC voltages and currents

27. Question

A transformer cannot work on the DC supply because __________________

There is no need to change the DC voltage
A DC circuit has more losses
Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero
Cannot be determined

28. Question

Turns ratio of the transformer is directly proportional to ____________

Resistance ratio
Currents ratio
Voltage ratio
Not proportional to any terms

29. Question

It is possible to attain maximum efficiency in a transformer when the ______

core losses are equal to rated full load copper losses
core losses are more than rated full load copper losses
core losses and full load copper losses are constant
copper loss also becomes constant

30. Question

The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The total losses at this condition is?

408W
4.08kW
4.08kW
2.04kW

31. Question

If Im is the maximum value of a sinusoidal voltage, what is the instantaneous value?

i = \( \frac{lm}{2} \)
i = Imsinθ
i = Imcosθ
i = Imsinθ or i = Imcosθ

32. Question

What is the correct expression for the rms value of current?

I_rms = \( \frac{lm}{2}\)
I_rms = \( \frac{lm}{\sqrt{2}}\)
I_rms = \( \frac{lm}{4}\)
I_rms = Im

33. Question

If maximum value of current is 5√2 A, what will be the value of RMS current?

10 A
5 A
15 A
25 A

34. Question

If the maximum value of the current is 5√2 A, what will be the value of the average current?

10/π A
5/π A
15/π A
25/π A

35. Question

What is the correct expression of ω?

ω = 2π
ω = 2πf
ω = πf
ω = 2f²

36. Question

Find the value of ω if the frequency is 5Hz?

3.14 rad/s
31.4 rad/s
34 rad/s
341 rad/s

37. Question

When one sine wave passes through the zero following the other, it is _________

Leading
Lagging
Neither leading nor lagging
Either leading or lagging

38. Question

Find the value of the instantaneous voltage if the resistance is 2 ohm and the instantaneous current in the circuit is 5A.

5V
2V
10V
2.5V

39. Question

If the impedance of a LC circuit is 8.54 Ohms and the r.m.s. voltage of the source V_rms = 110V, what is the r.m.s. current?

11.2A
12.9A
13A
14.9A

40. Question

A resistance of 7 ohm is connected in series with an inductance of 31.8mH. The circuit is connected to a 100V 50Hz sinusoidal supply. Calculate the current in the circuit.

2.2A
4.2A
6.2A
8.2A

41. Question

Which, among the following, is the correct expression for φ.

\( \scriptsize \phi = tan^{-1} \left( \normalsize \frac{X_L}{R} \right)\)
\( \scriptsize \phi = tan^{-1} \left( \normalsize \frac{R} {X_L}\right)\)
\( \scriptsize \phi = tan^{-1} X_L \: \times \: R\)
\( \scriptsize \phi = cos^{-1} \left( \normalsize \frac{X_L}{R} \right)\)

42. Question

For an RL circuit, the phase angle is always ________

Positive
Negative
0
90

43. Question

What is the resonant frequency of ac circuit?

\( \frac{1}{\sqrt{LC}} \)
\( \sqrt{\left( \frac{L}{C}\right)} \)
\(\scriptsize \sqrt{LC}\)
\( \scriptsize LC \)

44. Question

What is impedance at resonance?

maximum
minimum
zero
cannot be determined

45. Question

What is the resonance condition?

When X_L > X_C
When X_L < X_C
When X_L = X_C
When X_C = Infinity

46. Question

If in an alternating current circuit, resistance is 5 ohm, capacitive reactance is 12 ohm, what is the impedance?

5 ohm
10 ohm
12 ohm
13 ohm

47. Question

If in an alternating current circuit, capacitance of 30 µF is connected to a supply of 200V, 50Hz. Find the current in the circuit.

1.38 A
1.89 A
1.74 A
0.89 A

48. Question

Find the total voltage applied in a series RLC circuit when i = 3mA, V_L = 30V, V_C = 18V and R = 1000 ohms.

3.95V
51V
32.67V
6.67V

49. Question

In an AC circuit, resistance 50 Ω, inductance 0.3 H and capacitance 15 μF is connected to an AC voltage source 25 V, 50 Hz. Determine the inductive reactance in the circuit.

36 ohm
94 ohm
125 ohm
140 ohm

50. Question

Around 1911, Rutherford suggested a planetary model of atomic structure. Which of the following was not a proposition of this model?

Electrons revolve in circular orbits around the nucleus
Nucleus consists of protons and neutrons
Mass of atom is concentrated in the nucleus
Most of the volume in an atom is void

51. Question

Which of the Bohr’s postulates was incorrect?

Energy of electrons is quantized
Momentum of electrons is quantized
Electrons release energy when shifting from excited state to ground state
Electrons revolve around the nucleus in fixed circular orbits

52. Question

Number of atomic orbitals in nth shell is:

n²
2n²
2n + 1
n – 1

53. Question

_________ have the same mass number, but different nuclear charge.

Isotones
Isobars
Isotopes
Isoemtropic

54. Question

The half-life period of a radioactive substance is best determined by counting the number of alpha particles emitted per second in a Geiger Muller counter from its known quantity. If the half-life period of a radioactive substance is one month, then?

it will completely disintegrate in two months
l/8th of it will remain intact at the end of four months
3/4th of it will disintegrate in two months
it will completely disintegrate in four months

55. Question

A radioactive isotope undergoes decay with respect to time following __________ law.

logarithmic
exponential
inverse square
linear

56. Question

The half-life period of a radioactive element is 100 days. After 400 days, one gm of the element will be reduced to __________ gm.

\( \frac{1}{2} \)
\( \frac{1}{4} \)
\( \frac{1}{8} \)
\( \frac{1}{16} \)

57. Question

The uncertainty in the location of a particle moving with velocity 7.28 X 10⁷m /s is two times its de-Broglie wavelength. What is the uncertainty in measuring the velocity?

5.79 x 10⁶ m/s
6.12 x 10⁶ m/s
7.63 x 10⁶ m/s
8.45 x 10⁶ m/s

58. Question

The ratio of neutrons to protons of an element having a mass number and atomic number of 80 and 40 respectively is

4
3
2
1

59. Question

The immediate products of fission are called

fission splits
fission fragments
fission products
fission scatters

60. Question

During Einstein’s Photoelectric Experiment, what changes are observed when the frequency of the incident radiation is increased?

The value of saturation current increases
No effect
The value of stopping potential increases
The value of stopping potential decreases

61. Question

How does the intensity affect the photoelectric current?

As intensity increases, the photoelectric effect increases
As the intensity increases, the photoelectric effect decreases
As the intensity decreases, the photoelectric effect becomes twice
No effect

62. Question

Photoelectric emission could be explained by the ____________

Wave nature of light
Particle nature of light
Dual nature of light
Quantum nature

63. Question

The work function of lithium is 2.5 eV. The maximum wavelength of light that can cause the photoelectric effect in lithium is? Take Plank constant, h = 6.626 x 10^-34 J/s, c = 3 x 10⁸ m/s and Å = 10^-10m.

3980 Å
4980 Å
5980 Å
6980 Å

64. Question

Light of wavelength 3500 Å is incident on two metals A and B. Which metal will yield more photoelectrons if their work functions are 5 eV and 2 eV respectively?

A
B
A & B
C

65. Question

The Kinetic energy of a photoelectron emitted on shining a light of wavelength 6.2 x 10^-6m on a metal surface of work function 0.1 eV is

0.01 eV
0.02 eV
0.1 eV
1 eV

66. Question

What is the effect of intensity on the stopping potential?

As intensity increases, stopping potential increases linearly
As intensity increases, stopping potential decreases linearly
As intensity decreases, stopping potential increases exponentially
No effect

67. Question

A radio station broadcasts its programme at 219.3 metre wavelength. Determine the frequency of radio waves if velocity of radio waves is 3×10⁸m/s.

7.31 × 10^-7 Hz
1.954 × 10^-6 Hz
1.368 × 10⁶ Hz
6.579 × 10^-10 Hz

68. Question

The binding energy of an electron to a proton (i.e., hydrogen atom) is 13.6 eV. The loss of mass in the formation of one atom of hydrogen is _____________

2.42 x 10^-35 Kg
3.34 x 10^-35 Kg
4.58 x 10^-35 Kg
5.19 x 10^-35 Kg

69. Question

Calculate the de-Broglie wavelength of an electron which has been accelerated from rest on application of potential of 400volts.

0.1653 Å
0.5125 Å
0.6135 Å
0.2514 Å

70. Question

Calculate the minimum uncertainty in the momentum of a 4He atom confined to 0.40 nm.

2.02 x 10^-25 kg m/s
2.53 x 10^-25 kg m/s
2.64 x 10^-25 kg m/s
2.89 x 10^-25 kg m/s