What does a transformer change in an electrical system?
A Frequency
B Voltage
C Power
D Current
A transformer is primarily used to change the voltage of alternating current (AC) in a circuit. It can step up (increase) or step down (decrease) the voltage without altering the frequency of the signal. This makes it essential in power distribution.
Which of these types of transformers are designed to operate without oil?
A Distribution transformer
B Oil-filled transformer
C Dry-type transformer
D Power transformer
A dry-type transformer operates without the use of oil for insulation or cooling. It is typically used in smaller installations, providing benefits like environmental safety and ease of maintenance since no oil is involved.
What causes eddy current loss in a transformer?
A Magnetic flux
B Core vibrations
C Heat generation
D Conduction resistance
Eddy current loss occurs due to the induced currents in the transformer core when exposed to a changing magnetic flux. These currents generate heat, leading to energy loss. Laminated cores help minimize this loss.
What type of transformer is used for electrical isolation between circuits?
A Step-down transformer
B Power transformer
C Autotransformer
D Isolation transformer
An isolation transformer is used to isolate the electrical supply and provide safety by preventing electrical shock and limiting the flow of noise between circuits. It does not change voltage levels but isolates them electrically.
Which factor affects the efficiency of a transformer?
A Insulation type
B Core material
C Voltage rating
D Magnetic flux
The efficiency of a transformer is heavily influenced by the core material. High-quality core materials, like silicon steel, reduce core losses (eddy current and hysteresis losses), thus improving the overall efficiency of the transformer.
In a transformer, what happens when the secondary is open-circuited?
A No current in primary
B Secondary voltage drops
C High inrush current
D Current flows freely
When the secondary winding is open-circuited, no current flows through it. As a result, the primary current becomes negligible, and the transformer essentially draws very little power from the supply. This condition is used for certain testing procedures.
How does a transformer reduce energy loss during transmission?
A Improves impedance
B Reduces voltage
C Increases voltage
D Increases current
A transformer increases the voltage for long-distance transmission (step-up transformer), which decreases the current and minimizes the energy loss due to resistance in the transmission lines. Higher voltage leads to lower transmission losses.
What is the function of the winding in a transformer?
A Support voltage
B Produce magnetic field
C Reduce losses
D Provide insulation
The windings of a transformer create the magnetic field necessary for induction. When current flows through the primary winding, it generates a magnetic field that induces voltage in the secondary winding. The efficiency and capacity of the transformer depend on the winding configuration.
Which transformer type is most commonly used in power plants for voltage stepping up?
A Step-down transformer
B Distribution transformer
C Isolation transformer
D Power transformer
Power transformers are typically used in power plants to step up the voltage for efficient long-distance transmission. They are designed to handle high power levels and typically operate at high voltage ratings to reduce energy loss.
What type of current causes transformer core magnetization?
A AC
B Pulsed
C DC
D Direct
AC (alternating current) is responsible for transformer core magnetization. The fluctuating magnetic field generated by AC induces the magnetic flux in the core, which is fundamental to the operation of a transformer. DC would not produce this effect.
What is the typical use of an earthing transformer?
A Current boosting
B Impedance matching
C Protection against faults
D Voltage regulation
An earthing transformer is used to provide a stable neutral point in a system, helping to safely dissipate fault currents during unbalanced conditions. It is often used in systems where the neutral is not grounded.
What does the efficiency of a transformer depend on?
A Voltage regulation
B Load condition
C Core material
D Magnetic field strength
The efficiency of a transformer is most dependent on the load condition, i.e., the load at which it is operating. Transformers operate at peak efficiency near their rated load. The efficiency reduces at very low or very high loads.
What is the purpose of a step-up transformer?
A Decrease current
B Increase current
C Decrease voltage
D Increase voltage
A step-up transformer increases the voltage from the primary to the secondary winding. It is used in power transmission systems to increase voltage levels for efficient long-distance power delivery.
Which test measures the transformer’s copper loss?
A Impedance test
B Load test
C Short-circuit test
D Open-circuit test
A short-circuit test is performed by applying a reduced voltage to the transformer primary and measuring the current. This helps determine the copper losses in the windings under load conditions. The test is essential for calculating the transformer’s efficiency under operation.
What type of transformer is used to provide electrical isolation without changing voltage?
A Isolation transformer
B Power transformer
C Step-up transformer
D Distribution transformer
An isolation transformer provides electrical isolation between the primary and secondary circuits without changing the voltage. It is used for safety purposes, especially in sensitive electronic equipment, by preventing the passage of electrical noise and shock hazards.