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WorksheetsReview unit 4 part 3
Total questions: 53
Worksheet time: 13hrs 15mins
How much value of secondary current of a transformer with 3 Ampere passing in the primary winding and 200 volts if there is 100 volts in the secondary winding?
Is = 3 A
Is = 5A
Is = 0.166A
Is = 6A
Refer to the figure below, if the step-down transformer has a 3:1 ratio, what is the value of secondary voltage and current?
110V , 2A
80 V, 1.5A
120V, 1A
220V, 1A
What is the voltage applied on the load?
1000 Volts
500 Volts
250 Volts
65.5 Volts
Refer to figure below. What is the load current of transformer?
3 A
2 A
6 A
1 A
Refer to figure below. What is the primary voltage of this circuit and load power?
200 V
50 V
500 V
300 V
Power factor is defined as______________________
The property of a device or component to store an electrostatic charge
The ratio of true power to apparent power
The electrical property of a circuit that oppose any change in the current flowing in it
The force that moves free electrons along the conductor
What is called the states how much reactive load the circuit contains?
True power
Reactive power
Apparent power
Power factor
When there is an inductive load, some of the power supplied is not used to do work. This wasted power is called?
True power
Reactive power
Apparent power
Power factor
When there is a resistive load, the power supplied is used to do work. This type of power is called?
True power
Reactive power
Apparent power
Power factor
The power factor of the Capacitive load is__________________
11
0.0
0.1
1.0
The power factor is Large when reactive power is_________________
Zero
Low
High
1.0
The power factor is Small when reactive power is_________________
Zero
Low
High
1.0
The power factor of the resistive load is__________________
11
0
0.1
1.0 (100%)
The power factor is calculated by the following formula
PF = True Power / Reactive Power
PF = True Power x Reactive Power
PF = True Power / Apparent Power
PF = True Power x Apparent Power
What is unit of apparent power measured?
Watt
VAR
Volte amperes (VA)
All of above
What is unit of True power measured?
Watt
VAR
Volte amperes (VA)
All of above
What is unit of Reactive power measured?
Watt
VAR
Volte amperes (VA)
All of above
The apparent power is the sum of ________________
Active and reactive power
Active and apparent power
Reactive and apparent power
Active and true power
The formula used to calculate the active/true power in single phase transformer is_________________
Active Power = V x I x tan θ
Active Power = V x I x PF
Active Power = V x I x sin θ
Active Power = V / I x cos θ
What is the power factor value of a transformer with apparent power 100 VA and true power 90 watt?
1.11
0.11
0.9
90
How much is the active power of a transformer with apparent power 100 VA and power factor 0.9 ?
100 watts
100 vars
90 watts
90 vars
Refer to the figure below has an induction motor calculate the apparent power and line current. Given P = 49.2 W, PF = 0.7(70%) lagging
100.23 VA ,1.5 A
70.23 W ,0.59 A
70.23 VA ,0.59 A
100.23 W ,5.5 A
A welding transformer draws 100A at 200 V. a wattmeter Shows is taking 16 KW of power .Calculate the power factor
0.7
0.8
0.9
1.0
If a 240V circuit has a measured power of 86.4 W, and a power factor of 0.8 lagging, what is the circuit’s apparent power and line current?
100.23 VA ,0.5 A
108 VA ,0.45 A
108 W ,0.45 A
95 VA , 1.5 A
If a transformer supplied 120 V output to a load with a true power of 48.6 W and a power factor of 0.9 lagging, what is the circuit’s apparent power and line current?
54 VA ,0.45 A
108 VA ,0.45 A
108 W ,0.45 A
95 VA , 1.5 A
If an equipment transformer draws 50 A at 110 V and wattmeter readings show the transformer is taking 5170 W, what is the power factor?
0.8
0.7
0.94
1.0
Refer to the figure below; calculate the apparent power and line current. Given P = 49.2 W, PF = 0.9 (90%) lagging.
53.66 VA, 0.35 A
54.66 VA, 0.45 A
55.66 VA, 0.55 A
56.66 VA, 0.65 A
In a transformer, what should power out equal to?
Power rated
Rated capacity
Nameplate data
Power input
How are power transformer rated?
V
VAR
KVA
Watts
It is the amount of power the transformer can deliver without overheating
Rated capacity
Rated voltage
Rated current
Rated output
It is the ampacity of winding conductor in transformer ________________
Rated capacity
Rated voltage
Rated current
Rated output
It is the type and thickness of winding insulation in the transformer _______
Rated capacity
Rated voltage
Rated current
Rated output
It is the ability to dissipate heat in the transformer __________________
Rated capacity
Rated voltage
Rated current
Rated power
The power ratings for transformer and AC __________________ since most ac circuit have reactive load.
True power
Reactive power
Apparent power
Power factor
What is the difference between the power applied to the primary, and the output at the secondary of a transformer.
Power rated
Rated capacity
Power output
Power loss
What is the difference between the power applied to the primary, and the output at the secondary of a transformer.
Power rated
Rated capacity
Power output
Power loss
Why transformer is rated in VA?
Because most Ac circuits have resistive loads
Because most Ac circuits have Capacitive loads
Because most Ac circuits have Reactive loads
Because most Dc circuits have resistive loads
Why transformer is rated in VA?
Because most Ac circuits have resistive loads
To ensure the winding are able to carry the additional current for reactive load
Because most Ac circuits have active loads
To ensure the winding are able to carry load
The apparent power is the of ________________
Active power + Reactive power
Active power X Reactive power
Active power - Reactive power
Active X true power
Refer to figure shown transformer polarity. What is the relationship between primary and Secondary in Part (A)?
Diagonally opposite
Directly opposite
Parallel opposite
series opposite
Refer to figure shown transformer polarity. What is the relationship between primary and Secondary in Part (B)?
Diagonally opposite
Directly opposite
Parallel opposite
series opposite
The terminal leads of the transformer secondary winding are labelled as:
X1 & X2
S1 & S2
H1 & H2
P1 & P2
Refer to the figure below, how are the secondary transformer windings connected and what is the output across 1-2, 2-3, 1-3.
Parallel, V1-2 = 60V, V2-3 = 60V, V1-3 = 120V
Series, V1-2 = 60V, V2-3 = 220V, V1-3 = 220V
Parallel, V1-2 = 120V, V2-3 = 60V, V1-3 = 60V
Series, V1-2 = 60V, V2-3 = 60V, V1-3 = 120V
What is the output voltage between X1 and X4 if the primary voltage at terminal H1and H2 is 100 volts and H3and H4 is 100 volts?
25 volts
200 volts
50 volts
100 volts
What is the total voltage of a single phase transformer with two secondary winding connected in parallel, voltage rate 100V each?
50 volts
0 volt
100 volts
200 volts
What type of polarity is shown in figure below?
Parallel
Series
Additive
Subtractive
What is the total voltage of a single phase transformer with two secondary winding connected in series, voltage rate 100 volts each?
50 volts
200 volts
0 volt
100 volts
Refer to the figure. How are the secondary transformer windings connected and what is the output across 1-2, 2-3, 1-3:
Series, V1-2 = 48V, V2-3 = 96V, V1-3 = 96V
Parallel, V1-2 = 96V, V2-3 = 48V, V1-3 = 48V
Parallel, V1-2 = 48V, V2-3 = 48V, V1-3 = 96V
Series, V1-2 = 48V, V2-3 = 48V, V1-3 = 96V
Refer to figure below , what is the turn ratio if the primary winding and secondary winding are connected as shown in the figure.
1:1
2:1
1:2
4:1
If the H1 and X1 are of diagonally opposite, the transformer polarity is:
Parallel
Subtractive
Additive
Series
Refer to figure shown. What is the turn ratio if the primary winding and secondary winding are connected as shown in the figure.
4:1
1:1
1:2
2:1
Refer to figure below , what is the turn ratio if the primary and the secondary winding are connected as shown in the figure.
1:2
2:1
4:1
1:1
Which type of polarity is shown in the figure?
Parallel
Additive
Series
Subtractive
