Which of the following operations can be used to convert an alternative current dynamo into a direct current dynamo

• A. number of turns in the coil is increased
• B. strength of the field magnet is increased
• C. slip rings are replaced with split ring commutator
• D. coil is wound on a soft iron armature

(a) Explain briefly the purpose of earthing electrical appliance.

(b) Why does the light frorr bulb connected to a simple cell dim and eventually goes off after a while?

(c) A coil of incidence 0.007 H, a resistor of resistance 8 \(\Omega\) and a capacitor capacitance 0.001 F are connected in series an a.c. source of frequency \(\frac{500}{\pi}\)Hz. If the r.m.s voltages across the coil, the resistor and capacitor are 30v, 20v and 70v respectively;

(i) draw a vector diagram to illustrate the voltage across the components in the circuit.

(ii) Calculate the: (\(\alpha\)) r.m.s voltage of the source

(\(\beta\)) r.m.s current in the circuit;

(\(\gamma\)) power dissipated in the circuit.

iii) write down the sinusoidal equation for the r.m.s voltage, V, in terms of the time, t.

A galvanometer has a resistance of 5Ω. By using a shunt wire of resistance 0.05Ω, the galvanometer could be converted to an ammeter capable of reading 2Amp. What is the current through the galvanometer?

• A. 2mA
• B. 10mA
• C. 20mA
• D. 25mA

Temperature is the measure of the

• A. quantity of heat transferred into the molecules of an object
• B. mean kinetic energy of the molecules of the object
• C. kinetic energy of any individual molecule of the substance
• D. amount of work done by the molecules of the object

A uniform light rod is kept in horizontal equilibrium under the influence of fore forces as shown below, which of the following equations correctly represents the condition of equilibrium for the rod

• A. F1 + F2 = F3 + F4
• B. F1 + F2 - F3 + F = 0
• C. (F1 + F2)ab = (F3 + F4)cd
• D. F1a + F2b - F3c - F4d = 0

The temperature at which the water vapour present in the air is just sufficient to saturate air is

• A. Boiling point
• B. Ice point
• C. Saturation point
• D. Dew point

A piece of copper of mass 20g at a temperature of 110°C was dropped into a mixture of ice and water at 0°C. If the final steady temperature of the mixture is 0°C . Calculate the amount of ice that melted [Specific heat capacity of copper = 0.4 Jg\(^{-1}\)K\(^{-1}\), specific latent heat of fusion of ice = 330Jg\(^{-1}\)]

• A. 0.37g
• B. 0.60g
• C. 2.40g
• D. 2.70g

Which of the following statements about wave motion is correct?

• A. Electromagnetic waves are transverse
• B. Transverse waves do not require a medium for propagation
• C. Longitudinal waves vibrate perpendicular to the direction of travel
• D. All mechanical waves are longitudinal

Which of the following statements explain why hot soapy water is more effective in cleaning oil-stained dishes?

• A. The oil on the dishes repels the soap
• B. soap and heat decrease the surface tension of oil
• C. soap increases the surface tension of oil and water
• D. Hot water increases the surface tension of oil

What is the name given to the force of attraction between the nucleons in the nucleus of an atom?

• A. Gravitational force.
• B. Electrostatic force.
• C. Magnetic force.
• D. Nuclear force.