Waec 1990 Physics Past Questions And Answers
A charge of 1.0 x 10-5 Coulombs experience force of 40N at a certain point in space. What is the electric field intensity?
- A. 8.00 x 106NC-1
- B. 4.00 x 106NC-1
- C. 4.00 x 10-4NC-1
- D. 2.00 x 10-4NC-1
Which of the following statements about the atom is/are correct? I. Energy is needed to remove electrons from an atom II. Particles in the nucleus of an atom are bound together by strong forces. III. A large amount of energy is required to separate the particles in the nucleus of an atom. IV. When the nucleus of a uranium atom is split, the energy released accounts for the difference in the masses of the products and the parent nucleus
- A. I only
- B. I and II only
- C. I and III only
- D. II and IV only
Calculate the resistance of the filament of a lamp rates 240 V, 40 W
- A. 240Ω
- B. 360Ω
- C. 720Ω
- D. 1440Ω
Which of the following reduce(s) the effect of the back e.m.f. generated in the primary coil of an induction coil? The capacitor in the circuit II. The make and break contact in the circuit III. The ratio of turns in the secondary to that in the primary
- A. l only
- B. II only
- C. I and II only
- D. II and III only
Which of the following are contact forces? I. Force of tension II. Force of fiction, III. Magnetic force III Force of reaction.
- A. I,II and III only
- B. I, II and IV only
- C. I, III and IV only
- D. II, III and IV only
Birds can perch safely on overhead electric power cables without being electrocuted because
- A. birds can withstand high p.d. of the electric power cables
- B. any accumulated charge on the birds is quickly dissipated
- C. the feet of the birds are well insulated
- D. the current is a.c. and has particular direction
(a) Define the boiling point of a liquid.
(b) Describe an experiment to determine the boiling point of small quantity of a liquid.
(c) A piece of copper of mass 300 g at a temperature of 950°C is quickly transferred to a vessel of negligible thermal capacity containing 250 g of water at 25°C. If the final steady temperature of the mixture is 100°C, calculate the mass of the water that will boil away.
[Specific heat capacity of copper = \(4.0 \times 10^{2} Jkg^{-1} K^{-1}\); Specific heat capacity of water = \(4.2 \times 10^{3} Jkg^{-1} K^{-1}\); Specific latent heat of vaporization of steam = \(2.26 \times 10^{6} Jkg^{-1}\)
(d) State four other effects of heat on a substance other than expansion.
A rectangular coil of wire can rotate in a magnetic field. The ends of the coil are soldered to the two halves of a split ring. Two carbon brushes are made to press lightly against the split ring and when these are connected in circuit with a battery and rheostat, the coil rotates. This is a description of
- A. a suspended- coil vanometer
- B. a moving-cell ammeter
- C. a d.c generator
- D. an electric motor
A parallel beam of light is to be obtained from the headlamp ofa car. At which of the following positions should the source of light be placed from the pole of its spherical minor?
- A. At the focal point
- B. At the centre of curvature
- C. Beyond the centre of curvature
- D. Between the focal point and the pole
Water does not drip through an open umbrella of silk material unless the inside of the umbrella is touched. Which of the following phenomena is responsible for this?
- A. Surface tension
- B. Hydrostatic upthrust
- C. Viscosity
- D. Diffusion