he inside portion of part of a hollow metal sphere of diameter 20cm is polished. The portion will therefore form a?

• A. concave mirror of focal length 5cm
• B. concave mirror of focal length 10cm
• C. convex mirror of focal length 5cm
• D. convex mirror of focal length 10cm

A metal ball of weight W falls through a column of glycerine of viscosity V. If the ball experiences an upthrust U and terminal velocity is attained, then

• A. W > U + V
• B. W = U + V
• C. W = U - V
• D. W < U + V

Which of the following is not self-luminous?

• A. Incandescent electric bulb
• B. Incandescent fluorescent tube
• C. Lighted candle
• D. The moon

In the circuit diagram below, calculate the current in the 12Ω resistor if the cell has an emf of 12V and an internal resistance of 1?

• A. 0.8A
• B. 1.0A
• C. 1.6A
• D. 2.4A

(a)(i) Describe, with the aid of a circuit diagram, an experiment to measure the resistance of a wire given an ammeter of low resistance, a battery, a key, a rheostat, va high-resistance voltmeter and some connecting wires.

(ii) State two precautions necessary to obtain an accurate result.

(b) Using the experimental result and any necessary measurements, explain how the resistivity of the wire may be determined.

(c) Two cells, each of e.m.f. 2V and internal resistance 0.552, are connected in series. They are made to supply current to a combination of three resistors, one of resistance 20 connected in series to a parallel combination of two other resistors each of resistance 3Q. Draw the circuit diagram and calculate the:

(i) current in the circuit

(ii) potential difference across the parallel combination of the resistors

(iii) lost volts of the battery.

A machine requires 1000J of work to raise a load of 500N through a vertical distance of 1.5m. Calculate the efficiency of the

• A. 80%
• B. 75%
• C. 50%
• D. 33%

Find the standard deviation of the following data -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5

• A. 2
• B. 3
• C. ?10
• D. ?11

Two resistors 5Ω and 10Ω are arranged first in series and later in parallel to a 24V source, the ratio of total power dissipated in the series and parallel arrangements respectively is

• A) 5:3
• B) 1:50
• C) 50:1
• D) 3:5

A vapour is said to be saturated when

• A. more molecules return to the liquid than the amount that left it
• B. a dynamic equilibrium exists between the molecules of the liquid and the vapour molecules at a given temperature
• C. the vapour pressure is equal to the atmospheric pressure
• D. all molecules are moving with the same speed in all directions at a given temperature

An object is placed between two mirrors which are inclined at an angle of 120° and facing each other. Determine the number of images observed in the two mirrors

• A. 1
• B. 2
• C. 3
• D. 4