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WorksheetsMEC-Mock CBT 2
Total questions: 70
Worksheet time: 49mins
For household wiring and small units, the following should be used to protect people against electric shock.
RCD
ACB
OCB
MCCB
Water is used to extinguish
Class-A fires
Class-B fires
Class-C fires
Class-D fires
What is an important measure to avoid tripping?
Do not clean the work floor too often.
Protect humans against hazardous substances.
The workplace must be orderly and tidy.
Always wear suitable clothes.
What is a risk associated with the use of a forklift truck?
The load may become dirty.
Collision with persons when carrying loads that blocks the vision.
Hearing loss for nearby persons.
Fall from a height.
Static electricity can result in a spark which can cause an explosion or fire when it is exposed in the presence of _______________.
plastic
glass
water
fuel
Standards define a confined space as:
Is a space with limited entry and egress and enclosed in nature
A space that has limited or restricted access for entry and exit
A space that is not designed for continuous human occupancy
All the answers are correct
Which of these would NOT be defined as a confined space?
HVAC Ducts
Grain storage bins
Concrete cable Ducts
Electrical room
When should ladders be inspected?
Each day before use
At least once a week
At least once a month
At least once a year
When you discover a fire, you should…
Pull the fire alarm and call the fire department
Use a fire extinguisher to put out the fire, even if you’ve never used a fire extinguisher before
Stay in the building until you figure out a way to extinguish the fire
Run out of the building without warning others of the fire
Where should you aim a fire extinguisher nozzle when putting out a fire?
At the top of the fire
At the base of the fire
At the center of the fire
Away from the fire
Which of the following words signals the most severe hazards?
Warning
Danger
Caution
Notice
What is the first control measure to be considered when minimizing risk?
Stop the activity
Redesign the equipment
Wear personal protective equipment
Barrier of a safe area
What is the prime function of a residual current device (RCD)?
It ensures that sufficient electric current is available
It controls the electric voltage
It protects people against electric shock
It reduces electricity costs
What is the correct procedure for lifting an object?
Walk quickly to reduce carrying time.
Assess the weight before lifting.
Carry with one hand using a handle.
Keep feet close together on firm ground during lifting.
Consider the likelihood of someone being harmed and the type of resulting injury is the best action that describes how to assess the ______________________.
level of risk
number of task
intensity of sound
performance of machine
Full body harness is a body support device that distributes ___________ forces across the shoulders, thighs and pelvis.
foot injury
fall arrest
head bump
eye sight
Manual handling can result in fatigue, and lead to injuries of the:
eyes and ears
back, neck, shoulders and arms
heart
kidney and liver
Under what fault conditions does a RCD operate?
Phase to earth fault
Open circuit in an earth conductor
Open circuit fault in a phase conductor
Phase to neutral fault
The plot of a periodic waveform shows a regularly repeating pattern of values, each of which is called a --------------------:
peak value
peak-to-peak value
cycle
root-mean-square value
The time required for the values to rise and fall through one complete cycle is called the ------------ of the waveform.
period
frequency
maximum value
wavelength
The distance the waveform covers during the period is referred to as:
frequency
wavelength
period
maximum value
The ----------------------- of an ac waveform is the number of cycles that occur in one second.
wavelength
period
frequency
peak value
The relationship between frequency and period is as follows:
f = T
f = 1 ÷ T2
f = 1 ÷ T
f = 1 ÷ T3
If a waveform's period increases, its frequency -----------------------.
stays the same
decreases
increases
may increase or decrease
Suppose that 16 cycles of a waveform occur in 0.75 s. What is the waveform's period?
46.9 ms
21.3 s
21.3 ms
46.9 s
The ------------------------ value of an ac waveform is its value at a specific instant of time.
average
maximum
mean
instantaneous
The maximum value reached by an ac waveform is called its ---------------------.
peak value
peak-to-peak value
average value
effective value
The peak value of a waveform is sometimes also called its:
frequency
amplitude
wavelength
period
The -------------------------------------- is the difference between a waveform's positive peak value and its negative peak value.
effective value
average value
peak value
peak-to-peak value
The -------------------------------------------------- of an ac waveform is a measure of how effective the waveform is in producing heat in a resistance.
root-mean-square (rms) value or effective value
instantaneous value
peak value
peak-to-peak value
Using calculus, it can be shown that a sine wave's average value over a half cycle is equal to --------- times its peak value.
0.343
0.434
0.535
0.636
Where: Ν is the speed of rotation in r.p.m. P is the number of “pairs of poles”, the frequency output from an AC generator is:
Where, Vmax is the maximum voltage induced in the coil and θ = ωt, is the rotational angle of the coil with respect to time, The instantaneous values of a sinusoidal waveform Vi is given as
Vi = Vmax / sinθ
Vi = sinθ / Vmax
Vi = Vmax × sinθ
Vi = Vmax × sin2θ
Which one of the following statements is true?
In a resistor, current lags voltage by 90°.
In a resistor, voltage and current are in phase with each other.
In a resistor, voltage lags current by 90°.
In a resistor, current lags voltage by 180°.
Of the following pairs of equations, only one pair might be correct for a resistor's voltage and current. Which pair is it?
v = 5 V sin(200t + 30°) and i = 10 mA sin(200t − 60°)
v = 5 V sin(200t − 30°) and i = 10 mA sin(200t + 60°)
v = 5 V sin(200t − 30°) and i = 10 mA sin(200t − 30°)
v = 5 V sin(200t − 30°) and i = 10 mA sin(200t + 30°)
The angular frequency has the relationship:
ω = πf
ω = 2πf
ω = πT
ω = 2πT
Capacitive reactance is given by the equation:
XC = 1 ÷ (πfC)
XC = 1 ÷ (2fC)
XC = 1 ÷ (2πfC)
XC = 1 ÷ (2πC)
Inductive reactance is given by the equation:
XL = 2πfL
XL = πfL
XL = 2fL
XL = 2πL
What is the capacitive reactance of a 150-pF capacitor when the voltage across it has a frequency of 102 MHz?
65.4 Ω
10.4 Ω
96.1 Ω
32.7 Ω
What is the inductive reactance of a 6.8 mH inductor when the current through it has a frequency of 96.2 kHz?
1.31 kΩ
243 µΩ
654 Ω
4.11 kΩ
A peak current of 16.2 mAp flows through a 560-Ω resistor. What is the resistor's effective (rms) voltage drop?
12.8 Vrms
9.07 Vrms
6.41 Vrms
20.6 Vrms
Which one of the following statements is true?
In a capacitor, current lags voltage by 90°
In a resistor, voltage lags current by 90°
In a resistor, current lags voltage by 90°
In a capacitor, voltage lags current by 90°
What effect does an open circuit condition have on the current in a dc circuit?
A. Current increases
B. Current reduces
C. Current falls to zero
D. Current is unchanged
How is the armature in a dc generator connected to an external circuit?
A. Through slip rings.
B. Through a resistor
C. Through a commutator.
D. Through a fixed contact.
What effect produces a force of attraction when current is passed through a relay coil?
A. Heating.
B. Magnetic
C. Radiation.
D. Chemical.
What is the function of a potentiometer?
A. To produce a magnetic field.
B. To provide variable voltages.
C. To provide a heating element.
D. To add fixed resistance into a circuit.
RCD are designed to quickly and automatically disconnect a circuit when the electric current is not balanced between:
A. Line & Neutral
B. Line & Ground
C. Line & Earthing
D. Neutral & Ground.
What will be the terminal voltage of a fully charged nickel cadmium cell?
A. 2.1 V
B. 1.7 V
C. 1.5 V
D. 1.2 V
Calculate the Power in a circuit having a resistance value of 10 ohms and current flowing through the circuit is 5 Amps.
20 watts
500 watts
250 watts
2.5 watts
Cells are connected in parallel in order to increase the:
Life of the cells
Efficiency
Current Capacity
Voltage rating
Electrical energy will be converted into heat, this happens in _______________ circuit.
reactive
inductive
capacitive
resistive circuit
What material is used in the construction of low-power resistors used in many electronic circuits?
Carbon
silicon
germanium
aluminium
What is the insulating layer in a capacitor called?
electrolytic
Cathode
insulator
dielectric
What effect does an short circuit condition have on the current in a dc circuit?
Current increases
Current becomes excessive
Current fall to zero
Current is unchanged
When a single length of conductor at right angles moving through a magnetic field produces an EMF. This process is called _________________.
seebeck effect
chemical reaction
photoelectric
electromagnetism
Hydrometer is use to measure the ________________ of the battery.
voltage
current
state of charge
power
Ampere- hours is used to express the capacity rating of a _____________________.
generator
battery
transformer
capacitor
What is the most important thing to consider when climbing a ladder?
maintain the point contact
clean the ladder
paint the ladder
do not use ladder
The frequency of an ac waveform is the number of cycles that occur in one __________.
minute
hour
second
day
ω = 2πf, This formula refers to ___________.
impedance
angular frequency
reactance
wavelength
The average value of is equal to 0.636 of its _______________.
RMS
minimum value
flat value
peak value
Period is the time it takes for the wave to complete ____________.
1 cycle
2 cycles
3 cycles
4 cycles
From the formula XC = 1 ÷ (2πfC) , Xc refers to ___________.
impedance
inductive reactance
capactive reactance
conductance
In sine wave, the effective value is also called ______________.
RMS value
average
maximum
minimum
From the formula XL = 2πfL, ... XL refers to _______________________.
inductive reactance
capacitive reactance
impedance
conductance
Phase to earth fault is a requirement for ____________ to operate.
RCD
motor
panel
cable
Danger warning always mean which type of hazard?
minimal hazard
most severe hazard
not serious hazard
no hazard at all
___________________ causes fatigue that results to the injuries of back, neck, shoulders and arms .
walking
manual handling
climbing ladder
sitting in a computer
