29 Questions
How do the thin, insulated laminations in the transformer core help reduce eddy current losses?
They do not provide an easy path for current, reducing eddy currents
What is the primary reason for laminating transformer cores?
To minimize eddy current losses
If the input power to a transformer is 650 W and the output power is 610 W, what is the efficiency of the transformer?
93.8%
How can the power loss in a transformer be calculated?
By subtracting the output power from the input power
What is the primary purpose of a transformer?
To increase the voltage of an AC power source
What is the primary method for minimizing copper losses in a transformer?
Increasing the diameter of the wire used in the primary and secondary windings
Which of the following factors contribute to hysteresis losses in a transformer?
The core material and the frequency of the applied current
What is the primary reason for using laminated cores in transformers?
To minimize eddy current losses
Which type of transformer has no hysteresis losses?
Air-core transformers
What is the primary effect of eddy currents in a transformer core?
They increase the magnetizing current required
Which core material is best suited for minimizing hysteresis losses in a transformer?
Supermalloy (iron-nickel-molybdenum alloy)
What is the impedance transformation ratio of the transformer?
16:1
If the primary winding has a resistance of 25 Ω, what is the equivalent resistance of the secondary winding?
1.5625 Ω
If the primary winding is rated for a maximum voltage of 200 V, what is the maximum voltage that can be safely applied to the secondary winding?
50 V
Which of the following factors determines the maximum current that can be carried by a transformer winding?
The diameter of the wire used for the winding
If the transformer is operating at 100% efficiency, what is the power relationship between the primary and secondary windings?
The power in the primary winding is equal to the power in the secondary winding.
Which of the following statements about transformer ratings is true?
The maximum voltage that can be applied to a winding is determined by the type and thickness of the insulation used between the windings.
What is the purpose of impedance matching?
To ensure maximum power transfer to the load
In the first example given, where the source impedance is 6 Ω and the load impedance is 2 Ω, what is the power dissipated in the source?
54 W
What is the total circuit resistance in the second example, where the source impedance and load impedance are both 6 Ω?
6 Ω
If the load impedance is equal to the source impedance, what is the ratio of power dissipated in the source to power delivered to the load?
1:1
What is the circuit current in the second example, where the source voltage is 24 V and the total circuit resistance is 12 Ω?
2 A
If the load impedance is greater than the source impedance, what happens to the power transfer efficiency?
It decreases
What type of transformer configuration is described where a single coil of wire is 'tapped' to produce a primary and secondary winding?
Auto-transformer
In an auto-transformer with an adjustable tap, when the tap is at point A, how does the secondary voltage (Es) compare to the primary voltage (Ep)?
Es is less than Ep
If a voltage of 200 V is applied between points B and C in an auto-transformer, what is the secondary voltage available from points A and B?
100 V
What is the voltage available from points A and C in the auto-transformer, if a voltage of 200 V is applied between points B and C?
300 V
Which of the following is a brand name commonly used for adjustable auto-transformers?
Variac
Under what condition can a transformer be used at frequencies above its normal operating frequency?
For any frequency above its normal operating frequency
Learn about minimizing losses in electrical transformers by reducing the resistance of wires and managing copper losses. Understand the impact of diameter, weight, and dimensions on overall efficiency. Explore how reversing magnetism in a transformer's core leads to heat energy through hysteresis losses.
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