Which of the following is not a component of a d.c. electric motor?
- A. Commutator
- B. Field magnets
- C. Slip rings
- D. Armature
- E. Carbon brushes
The main function of the mouth of a telephone is to convert sound energy into
- A. heat energy
- B. light energy
- C. chemical energy
- D. electrical energy
- E. mechanical energy
CalcuIate the power delivered by a 3-phase line if its voltage and current at 132KV and 60A respectively.
- A. 2.38 x 107W
- B. 7.92 x 106W
- C. 3.96 x 106W
- D. 2.64 x 106W
- E. 7.92 x 104W
The diagram above represents a stationary wave set up in a string which is fixed at both ends. lf the frequency of the wave is 256Hz and the distance N1 N2 equals 1.5m, calculate the speed of the wave.
- A. 128ms-1
- B. 192ms-1
- C. 384ms-1
- D. 768ms-1
- E. 1536ms-1
The diagram above illustrates a variation of the displacement y of a wave particle with time t. lf the velocity of wave is 250ms-1, calculate the distance between two successive particles which are in phase
- A. 20m
- B. 2.5m
- C. 3.0m
- D. 5.0m
- E. 50.0m
The speed of sound in air is 330ms-1. How far from the centre of a storm is an observer who hears a thunder clap 2s after the lightning flash? (Neglect the time taken by light to travel to the observer)
- A. 1320m
- B. 660m
- C. 600m
- D. 330m
- E. 165m
A sound wave of velocity 350 ms-1 is directed towards the surface of water. lf the ratio of the wavelength of sound in water to that in air is 425:100, calculate the velocity on the wave in water
- A. 82.4ms-1
- B. 148.8ms-1
- C. 350.0ms-1
- D. 1487.5ms-1
- E. 3500.5ms-1.
The distance between two successive crests of a water is 1m. lf a particle on the surface of the water makes two complete vertical oscillations in 1 second, calculate the speed of the wave
- A. 0.5 ms-1
- B. 1.0 ms-1
- C. 2.0ms-1
- D. 3.0ms-1
- E. 4.0ms-1
A string of length 1.0 m vibrates in 10 loops. If the total mass of the string is 1.0 x 10-3 kg and the tension in it is 10N, calculate the frequency of the vibration.
- A. 50Hz
- B. 100Hz
- C. 250Hz
- D. 400Hz
- E. 500Hz
The walls and ceilings of many standard auditoria are covered with perforated pads to
- A. increase the intensity of sound waves
- B. increase the loudness of sound waves
- C. reduce the effect of reverberations of sound waves
- D. increase the interference effect of sound waves
- E. decrease the frequency of sound waves.
Which of the following instruments produces sound by the vibration of air column?
- A. Piano
- B. Guitar
- C. Flute
- D. Hand bell
- E. Talking drum
A converging lens of focal length 5cm forms a virtual image which is 10cm from the lens. How far from the lens is the object?
- A. 2.0cm
- B. 3.3cm
- C. 5.0cm
- D. 10.0cm
- E. 15.0cm
The refractive index of a medium relative to air is 1.8. Calculate the critical angle for the medium to the nearest degree.
- A. 18o
- B. 34o
- C. 45o
- D. 68o
- E. 90o.
When a ray of light is incident normally on an air- glass interface, its angle of refraction is
- A. 0o
- B. 42o
- C. 45o
- D. 60o
- E. 90o
A ray of light is incident on a glass block as shown in the diagram above. If the reflected and the retracted rays are perpendicular to each other, what is the refractive index of the glass relative to air.?
- A. 1.65
- B. 1.58
- C. 1.52
- D. 1.50
- E. 1.48
When a ray of light is incident normally on an air- glass interface, its angle of refraction is
- A. 0o
- B. 42o
- C. 45o
- D. 60o
- E. 90o.
The graph above shows the relationship between sin i and sin r for a ray of light in air incident on a liquid surface. If i and r are respectively angles of incidence and refraction, deduce the refractive index of the liquid from the graph
- A. 1.63
- B. 1.50
- C. 1.33
- D. 1.25
- E. 0.08
A boy walks away from a plane mirror at a speed of 3 ms-1 in a direction normal to the surface of the mirror. At what speed is his image approaching him?
- A. 8 9.0ms-1
- B. 6.0ms-1
- C. 4.5ms-1
- D. 1.5ms-1
- E. 0.0ms-1
A ray of light strikes a plane mirror at a glancing angle of 50o. Calculate the angle between the incident and reflected rays
- A. 20o
- B. 40o
- C. 50o
- D. 80o
- E. 100o.
In which of the following media would sound waves travel fastest?
- A. Kerosine
- B. Alcohol
- C. Water
- D. lron
- E. Air
The main reason why rice cooks faster in a pressure cooker than in cooking pot is that
- A. less heat escapes from the cooker
- B. the vapour pressure in the cooker is constant
- C. the rice is not affected by the draught over the cooker
- D. the vapour pressure in the cooker decreases
- E. the boiling point of water in the cooker is raised.