Question Library

(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) Define ionization potential. (b)(i) State the three types of emission spectra. (ii) Name one source each which produces each of the spectra stated in (b)(i). (c) In an x-ray tube, electrons are accelerated the target by a potential difference of 80 A Calculate the: (i) speed of the electron; ii) threshold wavelength of the electron. [h=6.6 x 10\(^{-34}\) Js; e = 1.6 x 10\(^{-19}\) C; Me = 9.1 x 10\(^{-31}\) d) An x-ray photon of frequency 4.5 x 10\(^{-18}\) strikes an. electron, assumed to be at rest. If t electron absorbs all the photon energy, calculate the speed acquired by the electron. [ h = 6.6 x 10\(^{-34}\) Js; Me = 9.1 x 10\(^{-31}\) kg ]

(a) Define boiling point of a liquid. (b) Describe how water in a round bottom flask could be made to boil without heating it. [diagram not necessary] (c) State three applications of expansion of metals. (d) A room with floor measurements 7m x 10 m contains air of mass 250 kg at a temperature of 34^\circC. The air is cooled until the temperature falls to 24^\circC. Calculate the: (i) height of the room; (ii) quantity of energy extracted to cool the room; (iii) which is higher: the calculated value or the actual energy needed to cool the room? Give a reason for your answer. [ Specific heat capacity of air = 1010 Jkg\(^{-1}\)K\(^{-1}\); density of air = 1.25 kg m\(^{-3}]

You are provided with a uniform metre rule of mass, M indicated on its reverse side, a knife-edge, a graduated measuring cylinder of known mass, \(M_1\) marked on it and other necessary apparatus. Read and record with values of M and \(m_1\). Balance the metre rule horizontally on the knife edge. Read and record the balance point as G. Tie a loop of thread around the neck of the measuring cylinder. Fill the cylinder with the sand provided to the 2cm\(^{3}\) mark. Record the volume, V, of the sand. Hang the cylinder at the 2 cm mark of the metre rule and adjust the position of the knife edge until the rule balances horizontally. Read and record the new balance position K. Determine the value of e and f. Determine the mass, \(m_2\), of the sand in the measuring cylinder. Hint: \(m_2\) = (\(\frac{\text {M x f}}{e}\)) - \(m_1\). Repeat the procedure by filling the measuring cylinder to the mark V = 4,6,8 and 10 cm\(^{3}\). In each case, ensure that the measuring cylinder is kept constant at the 2 cm mark on the metre rule. Tabulate your readings. Plot a graph with \(m_2\) on the vertical axis and V on the horizontal axis. Determine the slope, s, of the graph. State two precautions taken to ensure accurate results. (b)i. Determine the mass of 7.5 cm\(^{3}\) of the sand using your graph. ii. A gold coin of mass 102.0 g has a uniform cross-sectional area of 10.0 cm\(^{2}\). Calculate its thickness. [Density of gold=19.3 g cm\(^{-3}\)]

You are provided with a constantan wire, a2 \(\Omega\)standard resistor, an accumulator E, an ammeter A, a key K, and other necessary apparatus. Measure and record the emf of the accumulator provided Connect a circuit as shown in the diagram above. Close the key, read and record the ammeter reading \(l_o\) when the crocodile clip is not in contact with the Constantan wire. Open the key with the clip making contact with the wire, when d=90cm, close the key. Read and record the ammeter reading l. Evaluate d\(^{_1}\) Repeat the procedure for four other values of d=80, 70, 60, and 50 cm In each case, read and record the ammeter reading and evaluatre d\(^{_1}\). Tabulate your readings. Plot a graph with I on the vertical axis and d\(^{_1}\) on the horizontal aXIS. Determine the slope, S of the graph and its intercept, c, on the vertical axis. Evaluate k = \(\frac{c}{s}\) Using your graph, determine the current I when d=55cm. State two precautions taken to obtain accurate results. (b)i. Explain what is meant by the potential difference between two points in an electric circuit. ii. State two factors on which the resistance of a wire depends.

A load is pulled at a uniform speed along a horizontal floor by a rope at 45o to floor. If the force in the rope is 1500N, what is the frictional force on the load ?

A car starts from rest and moves with a uniform acceleration of 30ms-2 for 20s. Calculate the distance covered at the end of the motion

I. Small size. II. Low power requirement III. Not easily damaged by high temperature IV. Highly durable. Which of the above are the advantages of semiconductors?

A rocket is fired from the earth's surface to a distant planet. By Newton's law of universal gravitation, the force F will

An object moves in a circular path of radius 0.5m with a speed of 1ms-1 What is its angular velocity?

A block and tackle is used to raise a load of 250N through a vertical distance of 30m. What is the efficiency of the system if the work done against friction is 1500J?

If a load of 1 kg stretches a cord by 1.2cm, what is the force constant of the cord? {g=10ms-2}

An object of volume 1 m 3 and mass 2kg is totally immersed in a liquid of density 1 kgm-3 . Calculate its apparent weight.

The pressure at any point in a liquid at rest depends only on the

A balloon whose volume is 300m3 is filled with hydrogen. If the density of air is 1.3 kgm-3, find the upthrust on the balloon. [g = 10ms-2]