Waec Physics Past Questions For Year 1992
Question 41
Calculate the time in which 4.8 kJ of energy would be expended when an electric heater of resistance 1.8 x 103Ω is used on a 240 V mains supply. (Neglect heat losses to the surrounding).
- A. 150.0s
- B. 90.0s
- C. 36.0s
- D. 20.0s
- E. 2.7s.
Question 42
In a domestic circuit, electrical appliances and lamps are arranged in parallel across the mains so as to enable the
- A. same current to flow through the electrical appliances and the lamps
- B. maximum energy to be consumed at least cost
- C. same fuse to be used for the electrical appliances and the lamps
- D. voltage across the appliances not to be affected when the lamps are switched on and off
- E. heat losses to be minimized
Question 43
Calculate the length of a constantan wire of cross- sectional area 4 π x 10-8m2 and resistivity 1.1 x 10-6 Ω m required to construct a standard resistor of resistance 21 Ω. [Take π = 22/7]
- A. 0.42m
- B. 2.40 m
- C. 6.25 m
- D. 183.75 m
- E. 590.00 m
Question 44
Which of the following is not a consequence of hydrogen bubbles covering the copper plate of a primary cell?
- A. Polarization
- B. Local action
- C. Formation of hydrogen electrode
- D. Increase in the resistance of the cell
- E. Generation of less current by the cell
Question 45
Calculate the rate at which energy is used up in the circuit illustrated by the diagram
- A. 0 W
- B. 2 W
- C. 4 W
- D. 8 W
- E. 16 W
