SECTION AMultiple Choice: This section comprises FIFTY questions. Choose the corresponding letter of the correct response to each question below. Each question is worth 1 mark

1. Doubling both the voltage and resistance in a parallel or series circuit will cause the current flow to (A) double(B) halve(C) remain unchanged(D) quadruple

2. Which of the following materials has a negative temperature coefficient?

(A) Brass (B) Silicon (C) Iron (D) Copper

3. The r.m.s value of a sinusoidal alternating voltage is

(A) 0.318 peak value(B) 1.414 peak value (C) 0.707 peak value(D) 0.77 peak value

4.

In the above diagram Lamps R and S are identical.A volt meter connected across Lamp S

should read

(A) one quarter of the applied voltage(B) one third of the applied voltage(C) one half of the applied voltage(D) the total applied voltage

5. From which of the following is electricity chemically produced?(A) photo cell(B) Carbon(C) Batteries(D) Generators

6. In order to connect Battery X and Battery Y in parallel, their terminals should be connected

(A) +X with +Y and –X with –Y(B) +X with –Y and –X with +Y(C) –X with +Y(D)–Y with +X

7. It is advisable, not to use Water for extinguishing electrical fires because water

(A) may cause corrosion(B) may transmit shock to the user(C) may damage wire insulation(D) will not extinguish the fire

8. Which of the following is true for TWO resistors connected in parallel?

(A) The current flow through each resistor is the same.

(B) The voltage across each resistor is the same.

(C) The combined value of the resistors is equal to the sum of the individual values.

(D) Each resistor has the same resistance value.

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9. Four 24V batteries are first connected in series and then in parallel. The total voltage is (A) Four times greater in parallel than in

series (B) Four times smaller in series than in

parallel(C) The same in both connection(D) Four times smaller in parallel than in

series

10. What is the expected current drawn by an electric cooker rated at 12KW/230 volts?

(A) 19 Amps(B) 48.5 Amps(C) 52.17Amps(D) 95 Amps

11. An open circuit has the effect of

(A) Infinitely high resistance and zero current

(B) Zero resistance and excessive current

(C) Excessive current and excessive heat

(D) Zero resistance and excessive voltage drop

12. A secondary cell is one which(A)has an internal resistance of 0.5

ohms(B) cannot be recharged(C) when in use will not deteriorate(D)Can be recharged

13. Silver is a very good conductor of electricity. It has (A) low permittivity(B) high conductivity(C) high resistivity(D) low permeability

14.

Which of the following would be true for any value of current flowing in the above circuit?(A) V1 = V2

(B) V1 < V2

(C) V1 > V2

(D) V1 ~ V2

15. The rate at which work is done is referred to as

(A) Energy (B) Torque (C) Power (D) Current

16. An electric stove rated at IKW, 200V, is accidentally connected to a 100V supply. What power would it now develop?

(A) 250W(B) 500W(C) 800W(D) 1000W

17.

The circuit above represents a(A) bell circuit(B) battery driven machine(C) lamp dimmer(D) potentiometer circuit

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18.

The ratio of the current in circuit ‘A’ to that of circuit ‘B’ is

(A) 1:5(B) 2:1(C) 5:1(D) 5:2

19. The voltage at the end of a supply line was only 90% of the supply voltage. This could be due to the

(A) cable being too large(B) cable overheating(C) Supply voltage being too low(D) resistance of the cable being too high

20. The formula for quantity of electricity in an electrical circuit is Q = It. The correct expression for ‘t’ is

(A) Q/I(B) Q + t(C) QI(D) Qi

21. Primary cells are those which (A) consist of two negative electrodes(B) Can be recharged(C) Carry an open circuit voltage of 1.5V(D) Cannot be recharged

22. The power dissipated by a 50Ω resistor which is connected to a 24V d.c. supply is(A) 10.00w(B) 11.52w(C) 54.00w(D) 360.00w

23. A variable resistor can be connected as a potentiometer and as a (A) varactor(B) rheostat(C) fuse(D) switch

24. External energy such as heat, light or electricity can cause electrons in the valence shell to become (A) charged (B) stationary(C) trapped(D) free

25. The internal resistance of a cell having an e.m.f. of 2V and a terminal voltage of 1.8V when supplying a current of 20A is(A) 0.01Ω(B) 0.05Ω(C) 0.10Ω(D) 0.15Ω

26. How many amperes of electric current are equivalent to 600 milliamperes?(A) 0.06A(B) 0.6A(C) 6A(D) 60A

27. The alloy known as constantan is used in standard resistors because in case of a moderate rise in temperature it’s resistance(A) increases appreciably(B) Decreases appreciably(C) Is hardly affected(D) Fluctuates

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28.

The two suspended electrical charges illustrated above would

(A) attract each other(B) repel each other(C) rotate (D) Vibrate

29. The total resistance of two resistors having the same value and connected in parallel in a circuit would be

(A) three times the ohmic value of one

(B) two times the ohmic value of one(C) the same ohmic value of one(D) half the ohmic value of one

30. Which of the following colour codes shows the correct value for a resistor of 1000 ohms?

(A) Brown, black, red(B) Brown Brown, red(C) Brown, brown, orange(D) Brown, orange, brown

31. Which of the following conditions would present a low resistance path in an electrical circuit?

(A) An open circuit(B) A short circuit(C) A series circuit(D) A blown fuse

32. A person who gets an electrical burn should immediately (A) Apply mercurochrome ointment

to the area(B) Apply gentian violet to the area (C) Rub the area with petroleum

jelly(D) Run cold water over the area33. The resistance of a conductor is 0.05 ohms. What current is required to pass through it to give a 6 Volt drop?

(A) 30A(B) 40A(C) 60A(D) 120A

34. Electrical generating utilities in the Caribbean distribute power at frequencies of

(A) 30 or 40Hz(B) 50 or 60Hz(C) 70 or 80Hz(D) 90 or 100Hz

35. An ‘electrical shock’ is a physical sensation caused by the

(A) amount of current that can result in serious damage to the muscles of a persons body

(B) changes in temperature of a person’s body

(C) Current passing through the chest region of the body

(D) Reaction of the nerves to electric current

36. Which of the following are units of energy?I. LumenII. JoulesIII. Kilowatt Hours

(A) I and II only(B) I and III only(C) II and III only(D) I, II and III

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37. The colour bands on a resistor are red, orange, red. The coded value is

(A) 0.23kΩ(B) 2.30kΩ(C) 23.00kΩ(D) 232kΩ

38. The frequency of an alternating current source is the

(A) radian(B) voltage variations in one

revolution(C) number of cycles in one second(D) Completion of a set of specific

changes

39. Which of the following solutions is used as the electrolyte in a simple cell?(A) Copper sulphate (B) Zinc sulphate(C) Sulphuric acid(D) Ammonium chloride

39. The collection of hydrogen bubbles around the carbon electrode in a carbon-zinc cell is called(A) amalgamation(B) local action(C) ionization(D) polarization

40. What is the peak value of a 240V a.c. supply?

(A) 152.8V(B) 169.6V(C) 339.4V(D) 376.7V

41. To measure the voltage across a load, one would connect a/an

(A) Voltmeter in series with the load

(B) Ammeter in series with the load (C) Voltmeter across the load(D) Ammeter across the load

42. Which of the following colour codes shows the correct value for a resistor of 1000 ohms?

(A)Brown, black, red(B) Brown Brown, red(C) Brown, brown, orange(D)Brown, orange, brown

43. The power dissipated by a 50Ω resistor which is connected to a 24V d.c. supply is(A) 10.00w(B) 11.52w(C) 54.00w(D) 360.00w

44. Which of the following should be carried out last when treating an unconscious person who has had an electric shock?(A)Keeping airways to the lungs clear(B) Loosening tight clothing(C) Administering artificial respiration(D)Treating burns

45. In which of the following graphs is ohm’s law verified?

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46.

47. Which of the following precautions should be observed when checking the resistance of an electrical circuit with an ohmmeter?(A) Adjust the meter of f.s.d. before using(B) Adjust the meter to its lowest scale(C) Connect the meter to an a.c. source.(D) Ensure that no voltage is applied to the circuit while resistance is being measured.

48.

49. Which of the following circuits will dissipate the most power?

50. What effect does an ambient temperature greater than 30oC have on the current rating of a conductor?

(A) The current rating is decreased.(B) The current rating is increased.(C) The current rating remains

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unchanged.(D) The current rating is multiplied by the voltage drop

SECTION 2Candidates MUST answer ALL SIX questions in this section.

1. The figure above indicates three resistance readings taken by an ohmmeter. write the letters (X) , (Y) and (Z) . Next to EACH letter, write the value of reading indicated. (6 marks – 2 marks each)

X - ______________ Y - _________________ Z – ______________

2. The figure below shows the dials of a five dial watt-hour meter for a JPS customer. Calculate how much it would cost the customer for the one month period if he previous reading was 1141 and the rate is $9.25/KWH. (3 marks)

________________________________________________________________________________________________________________________________________________

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________________________________________________________________________________________________________________________________________________

3. (a) State Ohm’s Law and write the formula that represents Ohms Law. (2 marks) (b) Figure 1 shows a series parallel resistive circuit.

Figure 1Calculate the

(i) Total resistance when the switch S is closed (1 mark)

(ii) Total resistance when the switch S is open (1 mark)

(iii) Total current I when the switch S is closed (1 mark)

(iv) Maximum power developed in the 9Ω resistor. (3 marks)

Total 8 marks

4. (a) State TWO (2) reasons why cells are connected in parallel. (2 marks)

(b) State TWO advantages of an alkaline cell over a lead-acid cell. (2 marks)

(c) A commercial battery, with an open circuit voltage of 14.4V, has a

terminal voltage of 12.2V when supplying a current of 20A to a load.

Calculate the internal resistance of the battery. (4 marks)

Total 8 marks

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5. (a) Name THREE factors which affect the resistance of a metallic conductor. (4 marks)

(b) A copper cable 1500 m long, has a cross-sectional area of 25 x 10-6. The resistivity of copper is 1.7 x 10-6 Ω m.

Calculate the resistance of the cable (4 marks)

(c) Describe the difference between positive and negative temperature

coefficients of materials. (2 marks

6. (A) Make a neat sketch of an a.c. sine wave. (4 Marks)

(B) Indicate the following values on the sketch in part (A) above:

(i) One cycle

(ii) Positive Peak Voltage

(iii) Peak to peak voltage

(iv) R.m.s. voltage (4

Marks)

(C) Name TWO electrical characteristics of an a.c. sine wave. (2 Marks)

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