SECONDARY EDUCATION CERTIFICATEEXAMINA TION

11hours

1. You MUST use this answer booklet when responding to the questions. For each question, writeyour answer in the space provided and return the answer booklet at the end of the examination.

2. ALL WORKING MUST BE SHOWN in this booklet, since marks will be awarded for correctsteps in calculations.

Copyright © 2005 Caribbean Examinations Council®.All rights reserved.

1. A student was asked to investigate the variation in temperature of 2 kg of water initially at 30oe,when heat energy was supplied to it by an electric heater rated at 1400 W. The followingmeasurements were taken and recorded in Table 1.

Temperature of water, ate 30.0 40.0 51.0 62.5 72.0 80.0 89.0

Heating time, tis 0 60 120 180 240 300 360

Temperature change, ~a = (a - 30)tC 0

Energy supplied, Q = 1400t/J 0

(b) Plot on the graph page opposite a graph of energy supplied against temperature change.(11 marks)

(d) Assuming that the energy loss to the container and the surroundings is negligible, whatphysical quantity does this gradient represent?

(e) Determine the value of this quantity if 1 kg of water were used and state the physicalquantity this represents.

( 2 marks)

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(f) Water boils at 1OO°e. Calculate the heat energy which must be supplied in order tocompletely convert the 2 kg of water to steam.

[Specific latent heat of vaporization of water = 2.3 x 106 Jkg-1]

(b) The circuit shown in Figure 1 shows the interconnection between electrical devices, Band C, and voltage source A.

A fluorescent lamp is rated at l5W, l20V. Calculate the current which the lampdraws from the main supply.

(iii) When the lamp is lit, 4 W of the energy supplied is lost as heat. Calculate theefficiency of the lamp.

Figure 2 shows successive stages in the generation of a transverse wave on a stretchedslinky spring.

Hump.-formmg

Hump movestowards wall

the position of a crestthe position of a trough.

a) the direction of the waveh) the direction of hand movement needed to produce this wave.

( 3 marks)

(iii) Indicate on Figure 2A the direction of hand movement needed to produce alongitudinal wave. ( 1 mark)

(b) In a classroom demonstration a student uses a slinky spring to generate waves offrequency 5 Hz with 0.65 metres separation between successive crests. Determine thespeed of these waves.

Deduce whether the velocity of a sound wave will increase, decrease or remainconstant when the wave travels from a denser to a less dense medium, given thatthe frequency remains constant and the wavelength decreases.

(ii) Compare the waves produced on the slinky spring in part (b) with a typical soundwave in terms of the motion of the particles.

In Figure 3 below, a ship sends out pulses of high-frequency sound (ultrasound) whichare reflected from the sea bed and received at the ship every 1.2 x 10-2 seconds.

Cross sectionof ship

(c) A cyclist hangs his bicycle with the rear wheel in contact wi th the ground and the handleattached to a light string as shown in Figure 4. The entire assembly is in equilibrium.

tE- O.8m-71

I( 1.75m ---

(i) Indicate by drawing arrows on Figure 4 the forces acting on the bicycle.( 3 marks)

(iii) The bicycle has a mass of 20 kg. Use the result you obtained in Part (c) (ii) todetermine the tension in the string.

Code Live Wire Neutral Wire Earth Wire

InternationalInsulation Colour

(b) Fuses are sometimes used to protect electrical equipment from excess current. Explainhow a fuse works.

(c) A household has the following appliances

Heating iron rated at 1200 W, 110 VTelevision set rated at 70 W, 110 VElectrical fan 52 W, 110 V

(ii) These devices are in use for 4 hours per day. Calculate the energy consumed inkilowatt-hours in a 30-day month.

(iv) Assuming that these devices are connected in parallel across the mains supply,and are switch~d ON, calculate the TOTAL current drawn from the mains.

(v) Fuses are available with the following current ratings: 5A, lOA, 15A, 25A.Select a suitable fuse for protecting these devices.