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15. A working electric motor takes a current of 1.5A when the p.d across it is 250V. if its efficiency is 80%, the power output is
32. The electromagnetic wave that can produce a heating effect on the environment is
48. The force on a charge moving with velocity V in a magnetic field B is half of the maximum force when the angle between V and B is
16. A bread toaster uses a current of 4A when plugged in a 240 volts line. It takes one minute to toast slices of bread. What is the energy consumed by the toaster?
33. Calculate the refractive index of the material for the glass prism in the diagram below
49. The count rate of radioactive material is 800 count/min. If the half-life of the material is 4 days, what would the count rate be 16days later?
1. A transistor functions mainly as a
17. The cost of running five 60W lamps and four 100W lamps for 20hours if electrical energy costs ₦10.00 per kWh
25.
A resistance R is connected across the terminal of an electric cell of internal resistance 2Ω and the voltage was reduced to of its nominal value. This value of R is
50. In a semiconductor junction diode, as the depletion or barrier layer is forward-biased, the layer
2. The process of energy production in the sun is
18. The diagram below shows three capacitors C_{1}, C_{2}, C_{3} of capacitance 2F, 6F, and 3F respectively. The potential differences across C_{1}, C_{2 }and C_{3} respectively are;
34. At what frequency would a capacitor of 2.5μF used in a radio circuit have a reactance of 250Ω?
44.
Which of the following graphs shows the correct vector diagram for the circuit above?
3. Which of the following metals will provide the greatest shield ionizing radiation?
19. When a piece of rectangular glass block is inserted between two parallel plate capacitors, at constant plate area and distance of separation, the capacitances of the capacitor will
35.
What particles is X in the reaction above?
4. The particle emitted when 3919K decay to 3919K is
20. Zener diode is used for
36. The particle that is responsible for nuclear fission in a nuclear reactor is
I. pressure II. High pressure III. High P.D IV. Low P.D
Which combination of the above is true of the conduction of electricity through gases?
21
Given three inductor of inductance 5mH 10mH and 20mH connected in series, the effective inductance is
37. The carbon-granule microphone works on the principle of change in
6.
Which of the following graphs correctly represents the variation of mass of a given material deposited with time for constant current in faraday’s law of electrolysis?
22. If electrons are accelerated from rest through a potential difference of 90KV, what is the wavelength of the associated electron? [Me = 9.1×10-34Kg, e = 1.6×10-19C , h = 6.6×10-34Js]
38. The eyes control the amount of light reaching the retina by adjusting the
7. The current through a resistor in an a.c. circuit is given as 2sinwt. Determine the d.c. equivalent of the current.
23.
In the diagram below, the current I is
39.
The electric field between two-point charges is shown in the diagram above.
What types of charges are at X and Y?
8. At resonance, the phase angle in an a.c. circuit is
24.
In the circuit diagram below, the ammeter reads a current of 3A when R is 5Ω and 6A when R is 2Ω. Determine the value of x
40. A current of 0.5A flowing for 3hours deposits 2g of metal during electrolysis. The quantity of the same metal that would be deposited by a current of 1.5A flowing in hours is
9. Energy losses through eddy currents are reduced by using:
26. What is the angle of dip at the magnetic equator?
41. The energy associated with the photon of radio transmission at 3x105Hz is [h = 6.63×10-34Js]
10. A capacitor of 20x1012F and an inductor are joined in series. The value of the inductance that will give the circuit a resonant frequency of 200KHz is ?
[π^2 = 10]
27. The terrestrial telescope has one extra lens more than the astronomical telescope. The extra lens is for:
42. The percentage of the original nuclei of a sample of a radioactive substance left after 5 half-lives is
11. In the diagram below, determine the r.m.s current
28. The colours seen in soap bubbles are due to
43. From the generating station to each substation power is transmitted at a very high voltage so as to reduce
12. The primary coil of a transformer has N-turns and is connected to a 120V a.c. power line. If the secondary coil has 1000 turns and a terminal voltage of 1200 volts. What is the value of N?
29. To produce an enlarged and erect image with a concave mirror, the object must be positioned
45. Pure silicon can be converted to a p-type material by adding a controlled amount of
13. The force on a current-carrying conductor in a magnetic field is greatest when the
30. A concave mirror of radius of curvature 40cm forms a real image twice as large as the object. The object distance is
46. When alternating current given by I = 10sin(120πt) passes through a 12Ω resistor, the power dissipated in the resistor is
14. The magnetic force on a charged particle moving with velocity V is
31. The energy stored in a capacitor of capacitance 10μF carrying a charge of 100μC is
47. The maximum kinetic energy of the photoelectrons emitted from a metal surface is 0.34eV. if the work function of the metal surface is 1.83eV, find the stopping potential