How can the range of the voltmeter be extended?

(a) Outline two necessary conditions to be considered when selecting a cable for a particular circuit. (b) How is the resistance of the following materials affected by the increase in temperature? (i) Conductor (ii) Insulator

1. Outline two necessary conditions to be considered when selecting a cable for a particular circuit. (2 alama)
2. Outline two necessary conditions to be considered when selecting a cable for a particular circuit. (2 alama)
3. How is the resistance of the following materials affected by the increase in temperature? (i) Conductor (1 alama)
4. How is the resistance of an insulator affected by the increase in temperature? (1 alama)
5. How is the resistance of the following materials affected by the increase in temperature? (ii) Insulator (2 alama)

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Determine the value of resistance required to be connected in series with a 600 W kettle to cause voltage falling from 240 V to 220 V.

1. Determine the value of resistance required to be connected in series with a 600 W kettle to cause voltage falling from 240 V to 220 V. (5 alama)

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Give five reasons for electrical engineers to concentrate much on improving power factor of A.C circuit.

1. Give five reasons for electrical engineers to concentrate much on improving power factor of A.C circuit. (5 alama)

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A flux of 25 mWb links with a 1500 turns coil when a current of 3A passes through the coil. Calculate: (a) The inductance of the coil (b) The energy stored in the magnetic field (c) The average induced e.m.f if the current falls to zero in 150 ms

1. The inductance of the coil (2 alama)
2. The inductance of the coil (0 alama)
3. The energy stored in the magnetic field (2 alama)
4. The energy stored in the magnetic field (0 alama)
5. The average induced e.m.f if the current falls to zero in 150 ms (0 alama)
6. The average induced e.m.f if the current falls to zero in 150 ms (2 alama)

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(a) What does it imply when a material is said to have positive temperature coefficient? (b) A coil has a resistance of 10 Ω when its mean temperature is 20ºC and it is 20 Ω when its mean temperature is 50ºC. Find the temperature coefficient of the coil at 0ºC

1. What does it imply when a material is said to have positive temperature coefficient? (1 alama)
2. What does it imply when a material is said to have positive temperature coefficient? (0 alama)
3. A coil has a resistance of 10 Ω when its mean temperature is 20ºC and it is 20 Ω when its mean temperature is 50ºC. Find the temperature coefficient of the coil at 0ºC (4 alama)
4. A coil has a resistance of 10 Ω when its mean temperature is 20ºC and it is 20 Ω when its mean temperature is 50ºC. Find the temperature coefficient of the coil at 0ºC (0 alama)

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(a) Give the meaning of the term “armature reaction” as applied in D.C machines. (b) Why ammeter reaction is not suitable on d.c machine? Give two reasons. (c) Why is it not recommended for the d.c series motor to be switched ON at no load?

1. Give the meaning of the term “armature reaction” as applied in D.C machines. (0 alama)
2. Give the meaning of the term “armature reaction” as applied in D.C machines. (1 alama)
3. Why ammeter reaction is not suitable on d.c machine? Give two reasons. (2 alama)
4. Why ammeter reaction is not suitable on d.c machine? Give two reasons. (0 alama)
5. Why is it not recommended for the d.c series motor to be switched ON at no load? (2 alama)
6. Why is it not recommended for the d.c series motor to be switched ON at no load? (0 alama)

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A load of 30 KVA at unity power factor is used to supply primary voltage of 3300 V. if the step down transformer ratio is 15:1; Calculate: (a) Secondary voltage. (b) Primary current. (c) Secondary current.

1. Secondary voltage. (2 alama)
2. Secondary voltage. (0 alama)
3. Primary current. (2 alama)
4. Primary current. (0 alama)
5. Secondary current. (0 alama)
6. Secondary current. (2 alama)

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(a) A lamp rated 230 V gives an illumination of 6000 lux and takes 1.5 A from the mains. Calculate the efficiency of the lamp. (b) A school electrical technician wants to fix fluorescent lamps in a new classroom. He decided to use startles method in starting the lamps. Why does the technician decided to use startles method? Give two reasons.

1. A lamp rated 230 V gives an illumination of 6000 lux and takes 1.5 A from the mains. Calculate the efficiency of the lamp. (0 alama)
2. A lamp rated 230 V gives an illumination of 6000 lux and takes 1.5 A from the mains. Calculate the efficiency of the lamp. (3 alama)
3. A school electrical technician wants to fix fluorescent lamps in a new classroom. He decided to use startles method in starting the lamps. Why does (2 alama)
4. A school electrical technician wants to fix fluorescent lamps in a new classroom. He decided to use startles method in starting the lamps. Why does the technician decided to use startles method? Give two reasons. (0 alama)

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a) Identify two types of tests which must be carried out in transformer and for each type give reason for carrying such a test. b) When tested, a 20 kVA transformer was found to have 600 watts iron losses, and 700 watts copper losses when supplying full load at unity power factor. Calculate; (i) The efficiency of a transformer at unity p.f on full load. (ii) Output power on half load. (iii) Copper loss at half load.

1. Identify two types of tests which must be carried out in transformer and for each type give reason for carrying such a test. (6 alama)
2. The efficiency of a transformer at unity p.f on full load. (0 alama)
3. When tested, a 20 kVA transformer was found to have 600 watts iron losses, and 700 watts copper losses when supplying full load at unity power factor. Calculate; (i) The efficiency of a transformer at unity p.f on full load. (ii) Output power on half load. (iii) Copper loss at half load. (9 alama)
4. Copper loss at half load. (0 alama)

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Three coils, each having a resistance of 15 Ω and an inductance of 10 Ω, connected in star at a 400V, 3 phase 50Hz supply. a) Sketch a circuit for 3 phase star connected coils showing the position of phase and line voltages. b) Calculate: (i) The line current. (ii) Power factor. (iii) Power supplied.

1. Sketch a circuit for 3 phase star connected coils showing the position of phase and line voltages. (4 alama)
2. Calculate: (i) The line current. (ii) Power factor. (iii) Power supplied. (11 alama)
3. The line current. (0 alama)
4. Power supplied. (0 alama)

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a) Briefly describe three types of torques required for operation of indicating measuring instruments. b) A voltage coil of a dynamometer type wattmeter is connected across the load side and reads 200 W. If the load voltage is 245 V and the resistance of the voltage being 3612 Ω. Calculate the following: (i) True power across the load. (ii) Percentage error due to wattmeter connection.

1. Briefly describe three types of torques required for operation of indicating measuring instruments. (6 alama)
2. A voltage coil of a dynamometer type wattmeter is connected across the load side and reads 200 W. If the load voltage is 245 V and the resistance of the voltage being 3612 Ω. Calculate the following: (i) True power across the load. (ii) Percentage error due to wattmeter connection. (9 alama)
3. True power across the load. (0 alama)
4. Percentage error due to wattmeter connection. (0 alama)

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Calculate the flux density in the iron, absolute permeability of iron, relative permeability of iron and resistance of the magnetic circuit consisting of an iron ring of mean circumference of 80 cm with a cross sectional area of 12 cm2 throughout, if a current of 1 ampere in the magnetizing coil of 200 turns produced a total flux of 1.2 mWb in the core.

1. Calculate the flux density in the iron, absolute permeability of iron, relative permeability of iron and resistance of the magnetic circuit consisting of an iron ring of mean circumference of 80 cm with a cross sectional area of 12 cm2 throughout, if a current of 1 ampere in the magnetizing coil of 200 turns produced a total flux of 1.2 mWb in the core. (15 alama)

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