Question 1
Question
Electric current is described as a flow of
Answer
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protons
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neutrons
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electrons
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nucleus
Question 2
Question
Which one of the following identifies the sources of an electromotive force?
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Atomic, magnetic, thermal
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Chemical, atomic, thermal
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Chemical, magnetic, thermal
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Chemical, magnetic, atomic
Question 3
Question
When the current passing through a conductor is increased, the conductor’s temperature will:
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decrease
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stabilise
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fragment
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increase
Question 4
Question
The SI unit Henry is used for
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capacitance
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inductance
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frequency
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flux density
Question 5
Question
Ohm is the SI unit of measurement for:
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resistance
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voltage
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current
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charge
Question 6
Question
The SI unit for frequency is the
Question 7
Question
Resistance, potential difference and electrical current are expressed in the same order as units of:
Answer
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Ohms, Volts, Amperes
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Ohms, Watts, Amperes
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Ohms, Volts, Watts
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Watts, Volts, Ohms
Question 8
Question
Transpose the formula Z² = R² + X² to make R² the subject.
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R² = X² – Z²
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R² = Z² – X²
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R² = Z² + X²
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R² = X² x Z²
Question 9
Question
If the resistivity of aluminium is 2.65 x 10 -8 /metre, the resistance of a 65 metre length of 16mm2 aluminium conductor is:
Answer
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10.77Ω
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1.108Ω
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0.0108Ω
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0.108Ω
Question 10
Question
For the circuit shown, the total resistance is:
Question 11
Question
For the circuit shown, the power dissipated by the 15Ω resistor is:
Question 12
Question
The power dissipated in the circuit shown on the right would be:
Question 13
Question
When measuring current flow in a d.c. circuit, an ammeter must be connected:
Question 14
Question
Instrument B in the figure on the right measures the:
Question 15
Question
The strength of the magnetic flux produced when current flows in a conductor can be increased by:
Question 16
Question
Which one of the following shows the correct poles of the electromagnet when current flows in the direction shown?
Question 17
Question
What would be the effect on magnetic flux for the two equal, current-carrying conductors shown?
Answer
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The magnetic field would halve in strength, flowing in opposite directions
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The magnetic fields around each of the conductors would rotate independently
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The magnetic fields around the conductors would cancel each other out
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The magnetic field around the conductors would double in strength and flow in the same direction
Question 18
Question
A conductor of a simple alternator is 0.4m long and cuts a magnetic field with a magnetic flux density of 1.5 tesla at a velocity of 30m/s. The EMF induced in the conductor will be:
Question 19
Question
Which one of the following is the supply frequency if a sine wave has a periodic time of 20 milliseconds?
Question 20
Question
Refer to the figure shown. What does value A indicate?
Answer
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Average value of the waveform
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Periodic time of the waveform
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RMS value of the waveform
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Peak amplitude of the waveform
Question 21
Question
Which one of the following quantities can be described as a force?
Answer
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Gravity
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Current
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Resistance
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Energy
Question 22
Question
The formula shown is used to determine the force required given mass and acceleration. Which one of the following would be the acceleration for a mass of 20kg having a force of 10N applied? F = m x a
Answer
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200 m/s²
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0.5 m/s²
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5 m/s²
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50 m/s²
Question 23
Question
The power required to raise a mass of 8kg across a distance of 10m in 40 seconds is approximately:
Question 24
Question
A motor produces an output of 1.2kW when the input is 1.4kW; its efficiency is:
Question 25
Question
When used to ‘inch’ heavy equipment across the floor, a crowbar is being:
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a pulley
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a lift
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a machine
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a lever
Question 26
Question
Which one of the following instruments would be used to measure the line voltage for the star connected load?
Question 27
Question
In a four-wire, three phase system the phase voltage is 220v. The line voltage will be:
Question 28
Question
Which one of the following is the phase voltage for a star connected load if the line voltage is 400V?
Question 29
Question
Which one of the following instruments would be used to measure the line current for the delta connected load?
Question 30
Question
The line current feeding a delta load is 52A. The delta phase current will be:
Question 31
Question
The phase current in a delta load is 10A. The line current will be:
Question 32
Question
A balanced three phase star connected load draws a line current of 24A per phase. Which of the following is the approximate value of neutral current?
Question 33
Question
A d.c. motor in which the current remains constant in the field winding but varies in the armature winding is called:
Answer
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a compound machine
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an armature machine
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a shunt machine
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a series machine
Question 34
Question
If a single loop of wire connected to a commutator is rotated in a permanent magnetic field, the voltage measured at the commutator will be:
Answer
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d.c.
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a.c.
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intermittent
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unidirectional
Question 35
Question
The diagram shows a simple motor, indicating the field poles and direction of current flow. In which one of the following directions would the conductor move?
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Direction A
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Direction B
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Direction C
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Direction D
Question 36
Question
In a 400v to 4,000v step-up transformer the ratio of primary to secondary turns ratio will be:
Question 37
Question
Which one of the following components would cause current and voltage to behave as indicated in the sine wave shown?
Answer
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Rectifier
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Capacitor
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Inductor
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Resistor
Question 38
Question
The power triangle shown gives the relationship between powers in an a.c. circuit. Which one of the following is the unit used to measure Apparent power?
Question 39
Question
A circuit dissipates 3kW at a power factor of 0.7 when connected to a 230V a.c. supply. The current flowing in the circuit will be:
Question 40
Question
Power factor correction in circuits having lagging power factors can be achieved by connecting:
Answer
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inductors across the load
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resistors across the load
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resistors in series with the load
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capacitors across the load