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Worksheets141 S3 Transformers
Total questions: 30
Worksheet time: 3600secs
Name
Class
Date
1.
What are transformers rated in?
a)
A) Watts (W)
b)
B) Volts (V)
c)
C) Volt-Amperes (VA) or kiloVolt-Amperes (kVA)
d)
D) Amperes (A)
2.
How are transformers specified and rated?
a)
A) In kilowatts (kW)
b)
B) In megavolts (MV)
c)
C) In kiloohms (kO)
d)
D) In VA or kVA
3.
Which formula is used to find the rating of a single-phase transformer in kVA?
a)
A) kVA = V x I
b)
B) kVA = (V x I) / 1000
c)
C) kVA = v3 x (V x I)
d)
D) kVA = (v3 x (V x I)) / 1000
4.
What is the formula for finding the rating of a three-phase transformer in VA?
a)
A) VA = V x I
b)
B) VA = (V x I) / 1000
c)
C) VA = v3 x (V x I)
d)
D) VA = (v3 x (V x I)) / 1000
5.
If a transformer has a nameplate rating of 100 kVA, what does this represent?
a)
A) Primary voltage
b)
B) Primary current
c)
C) Transformer efficiency
d)
D) Transformer rating
6.
What is the primary voltage (High Voltage) of the transformer mentioned in the text?
a)
A) 11000 V
b)
B) 11 kV
c)
C) 415 V
d)
D) 139.1 A
7.
What is the secondary voltage (Low Voltage) of the transformer mentioned in the text?
a)
A) 11000 V
b)
B) 11 kV
c)
C) 415 V
d)
D) 139.1 A
8.
How is the primary current on the High Voltage (H.V.) side of the transformer measured?
a)
A) In kVA
b)
B) In amperes (A)
c)
C) In kilowatts (kW)
d)
D) In megavolts (MV)
9.
Which formula is used to calculate the transformer rating in kVA using primary voltage and primary current?
a)
A) kVA = V x I
b)
B) kVA = (V x I) / 1000
c)
C) kVA = v3 x (V x I)
d)
D) kVA = (v3 x (V x I)) / 1000
10.
Why might the calculated transformer rating using the three-phase formula differ slightly from the nameplate rating?
a)
A) Due to variations in voltage
b)
B) Due to variations in current
c)
C) Due to losses in the transformer
d)
D) Due to variations in frequency
11.
What is the primary function of a transformer?
a)
A) To convert DC electrical supply to AC
b)
B) To change the voltage and current of an AC electrical supply
c)
C) To generate electricity
d)
D) To store electrical energy
12.
What is the term for a transformer that increases the voltage?
a)
A) Step-up transformer
b)
B) Step-down transformer
c)
C) Voltage converter
d)
D) Current regulator
13.
What type of electrical supply do transformers work with?
a)
A) DC
b)
B) AC
c)
C) Both DC and AC
d)
D) None of the above
14.
What are the two coils wound around opposite sides of a transformer's iron core called?
a)
A) Primary and Secondary
b)
B) Input and Output
c)
C) Voltage and Current
d)
D) High-voltage and Low-voltage
15.
What does the turns ratio of a transformer refer to?
a)
A) The ratio of voltage and current
b)
B) The ratio of primary and secondary coil turns
c)
C) The ratio of power input to output
d)
D) The ratio of frequency and wavelength
16.
Which type of transformer has more turns on the secondary coil than on the primary coil?
a)
A) Step-up transformer
b)
B) Step-down transformer
c)
C) Voltage transformer
d)
D) Current transformer
17.
What is the typical efficiency range of transformers?
a)
A) 50-60%
b)
B) 70-80%
c)
C) 85-90%
d)
D) 95-98.5%
18.
What are the two main types of losses in transformers?
a)
A) Voltage losses and current losses
b)
B) Copper losses and iron losses
c)
C) Step-up losses and step-down losses
d)
D) AC losses and DC losses
19.
Which type of loss in transformers is proportional to the load current?
a)
A) Copper losses
b)
B) Iron losses
c)
C) Eddy current losses
d)
D) Hysteresis losses
20.
What causes eddy current losses in transformers?
a)
A) Resistance in the windings
b)
B) Magnetic induction in the core
c)
C) Voltage fluctuations
d)
D) High-frequency AC
21.
How are eddy current losses minimized in transformer cores?
a)
A) By increasing the load current
b)
B) By using solid metal cores
c)
C) By laminating the core
d)
D) By decreasing the number of turns in the coils
22.
What shape of transformer core lamination is the most common type?
a)
A) A shape
b)
B) B shape
c)
C) E shape
d)
D) I shape
23.
What purpose does oxidizing the laminations serve in transformer cores?
a)
A) Increases eddy current losses
b)
B) Reduces insulation
c)
C) Isolates the layers and reduces eddy currents
d)
D) Enhances magnetic induction
24.
What are the losses that occur in transformers that are classified under two types?
a)
A) Voltage losses and current losses
b)
B) Copper losses and iron losses
c)
C) Step-up losses and step-down losses
d)
D) AC losses and DC losses
25.
Which of the following is not a type of iron loss in transformers?
a)
A) Eddy currents
b)
B) Hysteresis
c)
C) Core saturation
d)
D) Magnetic losses
26.
Which video clip is mentioned in the text for further information on eddy currents?
a)
A) Exercise 141-S4-A1
b)
B) Transformer Losses
c)
C) Copper losses
d)
D) Eddy Currents
27.
What is the primary function of a step-down transformer?
a)
A) To increase the voltage
b)
B) To decrease the voltage
c)
C) To convert DC to AC
d)
D) To store electrical energy
28.
What are the two coils wound around opposite sides of a transformer's iron core called?
a)
A) Voltage and Current
b)
B) Input and Output
c)
C) Primary and Secondary
d)
D) High-voltage and Low-voltage
29.
What is the ratio between the magnitude of the voltages in the coils of a transformer?
a)
A) Turns ratio
b)
B) Voltage ratio
c)
C) Current ratio
d)
D) Resistance ratio
30.
What is the typical efficiency range of transformers?
a)
A) 50-60%
b)
B) 70-80%
c)
C) 85-90%
d)
D) 95-98.5%
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