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Worksheetsplacement online test 7
Total questions: 10
Worksheet time: 6mins
A transformer has a turns ratio of 4:1 (primary: secondary). If the primary voltage is 480 V, find the secondary voltage.
(a)
The primary winding of a transformer is connected to a 50 Hz supply. The core will have:
A) 50 cycles of flux per second
B) 100 cycles of flux per second
C) 50 cycles of flux per minute
D) 100 cycles of flux per minute
In a transformer, the magnetizing current is usually:
A) In phase with the applied voltage
B) Lagging the applied voltage by 180°
C) Leading the applied voltage by 90°
D) Lagging the applied voltage by 90°
A 200 V / 100 V, 5 kVA transformer has an efficiency of 98% at full load. Calculate the power loss at full load.
(a)
In a transformer operating under no-load condition, the no-load current:
A) Lags the voltage by 180°
B) Lags the voltage by 90°
C) Leads the voltage by 90°
D) Lags the voltage by slightly less than 90°
In a step-up transformer, which of the following remains constant?
A) Current
B) Voltage
C) Frequency
D) Power
In an ideal transformer, the power transferred from the primary to secondary is:
A) Increased by the square of turns ratio
B) Decreased by the square of turns ratio
C) Same as the primary power
D) Zero
In a transformer, the leakage flux links:
B) Only with secondary winding
C) Both primary and secondary windings
A) Only with primary winding
D) Neither primary nor secondary windings
The main purpose of providing a tap changer on the high voltage side of a transformer is:
B) To change power factor
D) To reduce core losses
C) To improve efficiency
A) To regulate voltage
If the supply frequency of a transformer is increased, keeping the voltage constant, then:
C) Core loss remains the same
B) Hysteresis loss decreases
A) Eddy current loss increases
D) Both eddy current and hysteresis loss increase
