Question 1

The primary reason for generating, transmitting, and distributing alternating current is because

Accepted Answer

A)  there are more applications for a.c. than for d.c. 
B)  its voltage levels may be changed easily using transformers 
C)  a.c. has lower losses than d.c. 
D)  a.c. is generally safer than d.c. 
A)  there are more applications for a.c. than for d.c. 
B)  its voltage levels may be changed easily using transformers 
C)  a.c. has lower losses than d.c. 
D)  a.c. is generally safer than d.c. B

Question 2

In the UK, voltages of 132 kV and 33 kV are used in the __________ system

Accepted Answer

A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution 
A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution B

Question 3

In the UK, voltages of 400 kV and 275 kV are used in the __________ system

Accepted Answer

A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution 
A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution A

Question 4

The instantaneous current, at a displacement angle of 30 degrees, of a sinusoidal current having an r.ms. value of 5 A, is

Accepted Answer

A)  2.5 A 
B)  3.54 A 
C)  4.33 A 
D)  6.12 A 
A)  2.5 A 
B)  3.54 A 
C)  4.33 A 
D)  6.12 A

Question 5

In the UK, voltages of 11 kV are used in the __________ system

Accepted Answer

A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution 
A)  transmission 
B)  primary distribution 
C)  secondary distribution 
D)  tertiary distribution

Question 6

A sinusoidal voltage, having a root-mean-square value of 400 V, has an average value of

Accepted Answer

A)  0 V 
B)  400 V 
C)  566 V 
D)  1132 V 
A)  0 V 
B)  400 V 
C)  566 V 
D)  1132 V

Question 7

A nominal supply voltage of 230 V (a.c.) represents the __________ of the supply

Accepted Answer

A)  average voltage 
B)  root-mean-square voltage 
C)  peak voltage 
D)  peak-to-peak voltage 
A)  average voltage 
B)  root-mean-square voltage 
C)  peak voltage 
D)  peak-to-peak voltage

Question 8

Transmission voltages are as high as possible to reduce the resulting

Accepted Answer

A)  load current 
B)  voltage drop along the transmission line 
C)  line losses 
D)  each of the above 
A)  load current 
B)  voltage drop along the transmission line 
C)  line losses 
D)  each of the above

Question 9

The highest practical speed of a 50-Hz alternator is

Accepted Answer

A)  1500 rev/min 
B)  3000 rev/min 
C)  6000 rev/min 
D)  12000 rev/min 
A)  1500 rev/min 
B)  3000 rev/min 
C)  6000 rev/min 
D)  12000 rev/min

Question 10

The value of voltage or current, at any specified displacement angle, during a complete cycle is called its

Accepted Answer

A)  instantaneous value 
B)  average value 
C)  amplitude 
D)  r.m.s value 
A)  instantaneous value 
B)  average value 
C)  amplitude 
D)  r.m.s value

Question 11

The length of a phasor usually represents the __________ of an a.c. voltage or current

Accepted Answer

A)  amplitude 
B)  average value 
C)  root-mean-square value 
A)  amplitude 
B)  average value 
C)  root-mean-square value

Question 12

A sinusoidal voltage, having a root-mean-square value of 400 V, has a peak-to-peak value of

Accepted Answer

A)  0 V 
B)  400 V 
C)  566 V 
D)  1132 V 
A)  0 V 
B)  400 V 
C)  566 V 
D)  1132 V

Question 13

A right-angled triangle has a hypotenuse of 10 m and an opposite of 6 m. What is the length of its adjacent side?

Accepted Answer

A)  4 m 
B)  8 m 
C)  11.7 m 
A)  4 m 
B)  8 m 
C)  11.7 m

Question 14

The angle of a phasor, measured counterclockwise from the normal, positive, axis represents a voltage's or current's

Accepted Answer

A)  displacement angle 
B)  phase angle 
C)  periodic time 
D)  frequency 
A)  displacement angle 
B)  phase angle 
C)  periodic time 
D)  frequency

Question 15

A four-pole alternator must rotate at what speed in order to generate a voltage at 50 Hz?

Accepted Answer

A)  12.5 rev/min 
B)  25 rev/min 
C)  750 Rev/min 
D)  1500 rev/min 
A)  12.5 rev/min 
B)  25 rev/min 
C)  750 Rev/min 
D)  1500 rev/min

Question 16

The maximum value of an a.c. waveform, in either the positive or negative sense, is called its

Accepted Answer

A)  instantaneous value 
B)  peak-to-peak value 
C)  amplitude 
D)  r.m.s value 
A)  instantaneous value 
B)  peak-to-peak value 
C)  amplitude 
D)  r.m.s value

Question 17

A current, having a root-mean-square of 13 A will do the same amount of work as a d.c. current of

Accepted Answer

A)  9.2 A 
B)  13 A 
C)  18.4 A 
A)  9.2 A 
B)  13 A 
C)  18.4 A

Question 18

Ammeters and voltmeters are calibrated to measure

Accepted Answer

A)  average values 
B)  root-mean-square values 
C)  peak values 
D)  peak-to-peak values 
A)  average values 
B)  root-mean-square values 
C)  peak values 
D)  peak-to-peak values

Question 19

What is the angle between the adjacent and hypotenuse of the above right-angled triangle?

Accepted Answer

A)  36.87 degrees 
B)  38.66 degrees 
C)  53.13 degrees 
A)  36.87 degrees 
B)  38.66 degrees 
C)  53.13 degrees

Question 20

Alternators driven by water turbines have __________ poles than those driven by steam, because water turbines rotate at a __________ speed.

Accepted Answer

A)  more, lower 
B)  more, higher 
C)  less, lower 
D)  less, higher 
A)  more, lower 
B)  more, higher 
C)  less, lower 
D)  less, higher

Exam 17: Introduction to Alternating Current

The primary reason for generating, transmitting, and distributing alternating current is because

In the UK, voltages of 132 kV and 33 kV are used in the __________ system

In the UK, voltages of 400 kV and 275 kV are used in the __________ system

The instantaneous current, at a displacement angle of 30 degrees, of a sinusoidal current having an r.ms. value of 5 A, is

In the UK, voltages of 11 kV are used in the __________ system

A sinusoidal voltage, having a root-mean-square value of 400 V, has an average value of

A nominal supply voltage of 230 V (a.c.) represents the __________ of the supply

Transmission voltages are as high as possible to reduce the resulting

The highest practical speed of a 50-Hz alternator is

The value of voltage or current, at any specified displacement angle, during a complete cycle is called its

The length of a phasor usually represents the __________ of an a.c. voltage or current

A sinusoidal voltage, having a root-mean-square value of 400 V, has a peak-to-peak value of

A right-angled triangle has a hypotenuse of 10 m and an opposite of 6 m. What is the length of its adjacent side?

The angle of a phasor, measured counterclockwise from the normal, positive, axis represents a voltage's or current's

A four-pole alternator must rotate at what speed in order to generate a voltage at 50 Hz?

The maximum value of an a.c. waveform, in either the positive or negative sense, is called its

A current, having a root-mean-square of 13 A will do the same amount of work as a d.c. current of

Ammeters and voltmeters are calibrated to measure

What is the angle between the adjacent and hypotenuse of the above right-angled triangle?

Alternators driven by water turbines have __________ poles than those driven by steam, because water turbines rotate at a __________ speed.

The Electron Theory of Electricity

Electric Current

Potential and Potential Difference

Resistance

Practical Conductors and Insulators

Effect of Temperature Change Upon Resistance

Ohms Law of Constant Proportionality

Series, Parallel and Series-Parallel Circuits

Cells and Batteries

Internal Resistance of Voltage Sources

Energy, Work, Heat and Power

Magnetism

Electromagnetism

Magnetic Circuits

Electromagnetic Induction

Capacitors and Capacitance

Series Alternating-Current Circuits

Power in Alternating-Current Circuits

Parallel Alternating-Current Circuits

Power Factor Improvement

Balanced Three-Phase Ac Systems

Filters

Alternators driven by water turbines have poles than those driven by steam, because water turbines rotate at a speed.