I. Small size.
II. Low power requirement
III. Not easily damaged by high temperature
IV. Highly durable.
Which of the above are the advantages of semiconductors?
- A. I,II and lll only
- B. ll,lll and lV only
- C. l, II and lV only
- D. l, ll, lll and lV
If a reverse-biased voltage is applied across a p-n junction, the depletion layer width is
- A. increased
- B. decreased
- C. constant
- D. halved
The p-n junction diodes can act as rectifiers because they
- A. conduct current when forward-biased
- B. conduct current when reverse-biased
- C. block current when forward-biased
- D. conduct current in both directions
A piece of radioactive material contains 1000 atmos. If its half -life is 20seconds, the time taken for 125 atoms to remain is
- A. 20 seconds
- B. 40 seconds
- C. 80 seconds
- D. 60 seconds
Which of the following CANNOT be deflected by both electric and magnetic fields?
- A. Gamma rays
- B. Alpha particles
- C. Wave particles
- D. Beta particles
The process of detecting a pin mistakenly swallowed by a child is X-ray
- A. Diagnosis
- B. Therapy
- C. Crystallography
- D. Mammography
A conductor of length 1m moves with a velocity of 50ms-1 at an angle of 30o to the direction of a uniform magnetic field of flux density 1.5Wbm-2. What is the e.m.f induced in the conductor?
- A. 37.5V
- B. 50.5V
- C. 75.0V
- D. 80.5V
The current output from of an a.c. source is given as I = 10 sin to t. The d.c equivalent of the current is
- A. 5.0A
- B. 7.1A
- C. 10.0A
- D. 14.1A
A particle carrying a charge of 1. 0 x 10-8C enters a magnetic field at 3.0x 10-2 ms -1 at right angles to the field. If the force on this particle is 1.8 x 10-8N, what is the magnitude of the field?
- A. 6.0x10-1T
- B. 6.0x10T
- C. 6.0x10-3T
- D. 6.0x10-4T
The fuse in an electric device is always connected to the
- A. neutral side of an electric supply
- B. earth side of an electric supply
- C. live side of an electric supply
- D. terminal side of an electric supply
A newly charged 12V accumulator can easily start a car whereas eight new dry cells in series with a effective e.m.f. of 12V cannot start the same car because
- A. The current capacity is high
- B. The current capacity is low
- C. it cannot be re-charged
- D. it cannot easily be connected to a car
Disperson of white light is the ability of white light to
- A. penetrate air, water and glass
- B. move in a straight line
- C. move around corners
- D. separate to its component colours
The use of lenses is Not applicable in the
- A. projector
- B. human eye
- C. periscope
- D. telescope
I. Rays of light travel from a less dense medium to a denser medium. II. The Angle of incidence is greater than critical angle. III. Rays of light travel from a denser medium to a less dense medium. Which of the statements above are conditions for total internal reflection to occur?
- A. I & II only
- B. I & III only
- C. II & III only
- D. II only
A glass block of thickness 10cm is placed on an object. If an observer views the object vertically, the displacement of the object is
- A. 3.33cm
- B. 5.00cm
- C. 6.67cm
- D. 8.50cm
After reflection from the concave mirror, rays of light from the sun converges
- A. at the radius of curvature
- B. at the focus
- C. beyond the radius of curvature
- D. between the focus and radius of curvature
The magnification of an object 2cm tall when placed 10cm in front of a plane mirror is
- A. 6.0
- B. 1.0
- C. 0.7
- D. 0.6
A pinhole camera is placed 300m in front of a building so that the image is formed on a screen 5cm from the the pinhole. If the image is 2.5cm high, the height of the building will be
- A. 25m
- B. 50m
- C. 100m
- D. 150m
Where can a man place his face to get an enlarged image when using a concave mirror to shave?
- A. Between the centre of curvature and the principal focus
- B. At the principal focus
- C. Between the principal focus and the pole
- D. At the centre of curvature
The characteristic of a vibration that determines its intensity is the
- A. Frequency
- B. Overtone
- C. Wavelength
- D. Amplitude
Which of the following factors will affect the velocity of sound?
- A. An increase in the pitch of the sound
- B. An increase in the loudness of the sound
- C. Wind travelling in the same direction of the sound
- D. A change in the atmospheric pressure at constant temperature