How long will it take to heat 3 kg of water from 28°C to 88°C in an electric taking a current of 6 A from an e.m.f. source of 220V?

• A. 96s
• B. 1.20s
• C. 570s
• D. 600s

Which of the following is most suitable for protecting the circuit of 2000W electric iron connected to a 250V mains?

• A. 13A
• B. 8A
• C. 5A
• D. 3A

The pressure of a gas when cooled at constant volume will decrease because the molecules

• A. collide less frequently with the walls of the container
• B. have the same average kinetic energy
• C. break up into smaller molecules
• D. decrease in number

(a) Sketch the magnetic flux pattern around a long; straight, current-carrying wire

(b) State two methods by which the sensitivity of a moving-coil galvanometer can be increased.

(c) A series RLC circuit comprises a 100-\(\Omega\) resistor, a 3-H inductor and a 4-\(\mu\)f capacitor. The a.c source of tile circuit has an e.m.f of 100V and a frequency of 160 Hz.

(i) Draw the circuit diagram of the arrangement. Calculate the:

(ii) capacitive reactance;

(iii) inductive reactance:

(iv) impedance of the circuit;

(v) current in the circuit;

(vi) average power dissipated in the circuit.

A body is projected with an initial velocity U at an angle O to the horizontal. The time taken by it to reach its maximum height is given by the expression

• A. \(\frac{2u \text{sin}\theta}{g}\)
• B. \(\frac{u^2 \text{sin}^2\theta}{2g}\)
• C. \(\frac{u \text{sin}\theta}{g}\)
• D. \(\frac{u \text{sin}\theta}{2g}\)

(a)(1) State the energy transformations which take place during the operation of a modern x-ray tube.

(ii) Distinguish between hard and soft x-rays.

(iii) State three uses of x-rays.

(iv) Mention one hazard of over-exposure to x-rays in a radiological laboratory, and indicate any two safety precautions.

(b) A possible fusion reaction is \(^2_1 H + ^2_1 H \to ^3_1H + ^1_1H + Q\)

where Q is the energy released as a result of the reaction. If Q = 4.03 MeV, calculate the atomic mass of \(^3_1H\) in atomic mass units. (\(^2_1 H = 2.01410 U; ^1_1H = 1.00783 U; 1U = 931 MeV\))

The effective capacitance between points X and Y in the diagram below is 1.0μF, What is the value of the capacitance C, measured in micro-farad?

• A. 5.0μF
• B. 4.0μF
• C. 3.0μF
• D. 1.0μF

A block of volume 3 x 10⁵m³ and density 2.5 x 10³ kg m^-3 is suspended from a spring balance with \(\frac{2}{3}\) of its volume immersed in a liquid of density 900 kg m^-3. Determine the reading of the spring balance [g = 10ms^-2]

• A. 0.18N
• B. 0.57N
• C. 0.75n
• D. 0.93N

a body moving at a constant speed accelerates when it is in

• A. rectilinear motion
• B. translational motion
• C. circular motion
• D. vibrational motion

Water boils at a lower temperature when heated at the top of a mountain than at sea-level because at the top of the mountain the

• A. saturation vapour pressure of water is higher than at sea-level
• B. sun adds more heat to the water
• C. temperature is lower than at sea- level
• D. pressure of the atmosphere is lower