The bond that forms a semiconductor is?
- A. covalent
- B. electrovalent
- C. ionic
- D. metallic
The energy E of a photon and it’s wavelength are related by Eλ = X. the numerical value of X is?
[h = 6.63 x 10-34js, c = 3 x 108 ms-1]
- A. 6.6 X 10-28
- B. 1.99 X 10-27
- C. 6.60 x 10-26
- D. 1.99 x 10-25
A radioactive substance has a half-life of 20 days what fraction the original radiation nuclei will remain after 80 days?
- A. (1)/32
- B. (1)/16
- C. (1)/ 8
- D. (1)/4
A 120 V, 60 W lamp is to be operated on 220 V a.c. the supply mains. calculate the values of non-inductive resistance that would be required to ensure that the lamp is run on current value.
- A. 100 Ω
- B. 200 Ω
- C. 300 Ω
- D. 500 Ω
The instrument that measures both a.c and d.c is?
- A. a current balance
- B. a moving current ammeter
- C. a moving iron ammeter
- D. an inverter
A 40 kW electric cable is used to transmit electricity through a resistor of resistance 2.0Ω at 800 V. The power loss as internal energy is?
- A. 4.0 x 102W
- B. 5.0 x 102W
- C. 4.0 x 103W
- D. 5.0 x 103W
A conductor has a diameter of 1.00 mm and length 2.00m. if the resistance of the material is 0.1Ω, its resistivity is?
- A. 2.55 x 105 Ωm
- B. 2.55 x 102 Ωm
- C. 3.93 x 10-6 Ωm
- D. 3.93 x 10-8 Ωm
If two charged plates are maintained at a potential difference of 3 kv, the work done in taking a charge of 600 µC across the field is?
- A. 0.8 J
- B. 1.8 J
- C. 9.0 J
- D. 18.0 J
A charge 50 µc has electric field strength of 360 NC-1 at a certain point. The electric field strength due to another charge 120 µc kept at the same distance apart and in the same medium is?
- A. 864 NC-1
- B. 150 NC-1
- C. 144 NC-1
- D. 18 NC-1
The production of pure spectrum could easily be achieved using a?
- A. glass prism with a pin
- B. triangular prism with two convex lens
- C. traingular prism only
- D. triangular prism with two concave lenses
When an object is placed between the principal focus and the optical center of a convex lens, it could be used as a?
- A. Simple microscope
- B. refecting lens
- C. compound microscope
- D. projector
A glass plate 0.9cm thick has a reflective index of 1.50. how long does it take for a pulse of light to pass through the plate?
[c = 3.0 x 10\(^8\) ms-1]
- A. 4.5 x 10-11s
- B. 4.5 x 10-10s
- C. 4 .5 x 10-12 s
- D. 3.0 x 10-10s
The instrument used by designers to obtain different color pattern is called?
- A. periscope
- B. sextant
- C. episcope
- D. kaleidoscope
The phenomenon of light bending round an obstacle is?
- A. diffraction
- B. refraction
- C. reflection
- D. polarization
In a large telecommunications auditorium, perforated absorbent materials are used to line the ceiling so as to
- A. Increase the reverberation of sound in the hall
- B. increase the amount of echo in the hall
- C. reduce the hight of the ceiling from the floor
- D. reduce the reverberation of sound in the hall
I. They should be identical
II. They should originate from the same source.
III. They should be coherent.
IV. They should be monochromatic.
from the statements above, the conditions for two waves to interfere are?
- A. I,II and III only
- B. I, III and IV only
- C. II, III and IV only
- D. I, II, III and IV
The blade of a hoe feel colder to touch in the morning than the wooden handle because the
- A. handle is a better conductor of heat than blade
- B. handle contains stored energy in form of heat
- C. blade is a better conductor of heat than the handle
- D. blade is placed at a lower temperature than the heat
I. Mass
II. Density
III. Temperature
IV. Nature of substance
which of the above affect diffusion?
- A. I and II only
- B. I,II and IV only
- C. II, III and IV only
- D. I, II, III and IV
I. Increase the melting point of the liquid.
II. Increase the boiling point of the liquid.
III. Decrease the melting point of the liquid.
IV. Decrease the boiling point of the liquid.
which of the statement above about the effect on increase in pressure in a liquid are correct?
- A. I and II only
- B. I and III only
- C. II and III only
- D. III and IV only
2 kg of water is heated with a heating coil which draws 3.5 A from a 200 V mains for 2 minutes. what is the increase in temperature of the water?
[specific heat capacity of water = 4200 jkg -1k-1]
- A. 30°
- B. 25°
- C. 15°
- D. 10°
I. Use a liquid with a high melting point.
II. use a liquid of high volume expansivity.
III. use a capillary tube of large diameter.
which of the above best describes how the sensitivity of a liquid-in-glass thermometer can be enhanced?
- A. I only
- B. II. only
- C. I and II only
- D. II and III only