31. An electron of mass 9.1 x 10−31kg moves with a speed of 2.0 x 106ms−1 round the nucleus of an atom in a Circular path of radius 6.1 x 1011 Calculate the centripetal force acting on the electron.
- A. 7.7 x 1047 N
- B. 6.0 x 10−8N
- C. 3.0 x 10−14N
- D. 1.3 x 10−26N
Correct Option: Answer is C
Centripetal force (Fr) = MV2/r
32. A device consumes 100 W of power when connected to a 120 V source. Calculate its resistance.
- A. 1.2Ω
- B. 12,000 Ω
- C. 20.0Ω
- D. 144Ω
Correct Option: Answer is A
R = v/I
= 120/100= 1.2Ω
33. Which property of a wave remains constant when the wave travels from one medium into another?
- A. Amplitude
- B. Wavelength
- C. Velocity
- D. Frequency
Correct Option: Answer is A
34. The anomalous expansion of water occurs in the range
- A. 0 °C to 100 °C
- B. 0 °C to 4 °C
- C. 4 °C to 100 C
- D. -4 °C to 0 °C
Correct Option: Answer is B
35. A ray of light travelling from a rectangular glass block of refractive index 1.5 into air strikes the block at an angle of incidence of 30. Calculate its angle of refraction.
- A. 48.6°
- B. 19.5°
- C. 20.0
- D. 45.0
Correct Option: Answer is A
n = sinI/sinr=sin30o/sinr
1.5 = sin30o/sinr
1.5 sin r = sin30o/1.5 = 0.5/1.5
sin r = 0.3333
= 48.6o
36. A rectangular piece of iron measuring 4 cm by 3 cm at 20oC is heated until its temperature increases by 100 C. Calculate the new area of the metal. [Linear expansivity of iron is 1.2x 10−5K−1]
- A. 12.0144 cm3
- B. 12.0346 cm3
- C. 12.0288 cm3
- D. 12.0173 cm3
Correct Option: Answer is B
Linear expansivity (α)
= A2−A1/A1θ
Original Area(A1) = 4 x 3 = 12
New Are (A2) = ?
Temp. rise (θ) = 100oC
A2 – 12 = 1200 x 1.2 x 10−5
A2 – 12 = 1440 x 10oC
A2 – 12 = 0.0144
A2 = 12.0144 cm2
37. Which of the following graphs gives the correct relationship between energy and mass when mass is converted to energy?
- A. A
- B. B
- C. C
- D. D
Correct Option: Answer is A
38. The diagram above illustrates an object moving in a circular path at a constant speed. Which of the arrows indicates the direction of linear velocity?
- A. z
- B. X
- C. Y
- D. W
Correct Option: Answer is A
39. Which of the following thermometers is used to measure the temperature of the human body?
- A. Thermocouple
- B. Alcohol-in-glass thermometer
- C. Gas thermometer
- D. Platinum resistance thermometer
Correct Option: Answer is A
40. In the diagram above, the time taken to trace a wave between P and Q is
- A. 2 periods
- B. 1 period
- C. 1 1/2 periods
- D. 1 1/4 periods
Correct Option: Answer is B
41. Which of the following materials does not serve as a safety device in electrical circuits?
- A. Connecting wires
- B. Earth wire
- C. Fuse
- D. Switch
Correct Option: Answer is A
42. Which of the following liquids has the highest surface tension?
- A. Soapy water
- B. Cold water
- C. Hot water
- D. oily water
Correct Option: Answer is D
43. The nucleon and proton numbers of a neutral atom of an element are 238 and 92 respectively. Determine the number of neutrons in the atom.
- A. 119
- B. 330
- C. 165
- D. 146
Correct Option: Answer is D
Neutron No (N) = 238 – 92
= 146
44. An instrument used to measure relative humidity is the
- A. hygrometer
- B. hydrometer
- C. pyrometer
- D. manometer
Correct Option: Answer is A
Hygrometer, instrument used in meteorological science to measure the humidity, or amount of water vapour in the air. Several major types of hygrometers are used to measure humidity.
45. The area under a velocity-time graph represents
- A. speed
- B. acceleration
- C. moment
- D. distance
Correct Option: Answer is D
The area under the velocity-time graph represents the distance travelled. Velocity-time graph for a car moving with uniform acceleration is a straight line and the area of the graph gives the distance travelled during a time interval.