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WorksheetsUnit 202 Revision #2
Total questions: 20
Worksheet time: 20mins
The relationship between the mass of a body (m), the applied force to the body (F) and the acceleration of the body (a) is given by the formula
Force = mass x acceleration, F = m x a
mass = Force x acceleration, m = F x a
acceleration = mass x Force, a = m x F
acceleration = mass / Force, a = m / F.
The SI unit of time is the second. Express 0.00001 seconds in a suitable sub multiple
10 milliseconds, 10 ms
100 milliseconds, 100 ms
100 microseconds, 100 μs
10 microseconds, 10 μs
In a magnetic circuit the magnetic field strength H is expressed in ampere turns/metre. H is calculated using the formula
H=nlI
H=lnI
H=nIl
H=Inl
The formula used to calculate the resistance (R) of a conductor, given its length (l), cross sectional area (a) and the constant of resistivity (r)
R=aρl
R=ρla
R=lρa
R=ρal
A simple alternator consists of a coil which is rotated in a permanent magnetic field.
The emf generated in the rotating coil is connected to a load via the-
commutator and brushes
flexible cables
slide rails and contacts
slip rings and brushes
If the input energy and output energy of a machine are known, the percentage efficiency of the machine is calculated using the formula
Efficiency = inputoutputX 100
Efficiency = outputinputX 100
Efficiency = outputinput x 100
Efficiency =
inputoutput x 100
The most common material used to manufacture brushes used in a.c. and d.c. rotating machines is
Copper
Carbon
Aluminium
Verulamium
The material used as an insulator on which overhead lines are suspended from pylons is
Glass
Mica
PVC
Rubber
Electric current is the flow of negatively charged particles called
protons
electrons
neutrons
atoms
In a domestic battery system linked to a PV installation the emf is produced by
heating effect
magnetic effect
chemical effect
movement effect
Insulating materials are materials which have atomic structures with
few free electrons
many free electrons
few free protons
many bound protons
The meters M1 and M2 connected in the circuit shown will measure
M1 = voltage
M2 = current
M1 = voltage
M2 = voltage
M1 = current
M2 = voltage
M1 = current
M2 = current
It is beneficial to use transformers to produce high voltages for energy transmission in order to
increase the speed of energy transmission
reduce the size of transmission line conductors
allow the use of less expensive insulating materials
increase the power generated
A body is accelerated at 2 m/s2 when a force of 10 newtons is applied to is, the mass of the body will be?
20 kg
10 kg
5 kg
2kg
A circuit has a resistance of 1.5Ω and runs at 90 Vdc, what is the power?
5.4 kW
1.2Kw
60w
135w
A d.c. machine has a power output of 1200 watts. The input current is 4A and the applied voltage is 375V. The efficiency of the machine will be
50%
80%
85%
90%
Two resistors of 20 ohms and 40 ohms are connected in series across a 120v d.c. supply, the current flowing in the circuit will be
20A
0.5A
5A
2A
The following are all parts of an electrical circuit
circuit breaker, load, switch
conduit, cable, cable clip
fuse, motor casing, cable insulation
trunking, switch, switch box
A charge of 4.7kC develops in 3.5 hours, what current is used?
377.7mA
1.34A
37.33A
37.3mA
what is 3.578 X 10-7 Ω in engineering notation?
35.78 μΩ
357.8 X 10-5 Ω
35.78 X 10-6 Ω
0.0000003578 Ω
