Transmission and Distribution Systems MCQs (Part-7)
What is the primary function of a step-up transformer?
A Increase voltage
B Control current
C Stabilize frequency
D Decrease voltage
The primary function of a step-up transformer is to increase the voltage from a lower value to a higher value, typically used for long-distance transmission. This helps reduce current and minimizes power loss due to resistance in the transmission lines.
What is a key characteristic of a step-down transformer?
A Increases voltage
B Decreases current
C Decreases voltage
D Regulates frequency
A step-down transformer reduces the voltage from high levels to lower levels, making the power suitable for residential or industrial use. It is critical in distributing electrical power efficiently and safely at usable voltage levels.
What happens when the primary voltage exceeds the secondary voltage in a step-up transformer?
A Power is lost
B Current increases
C Voltage increases
D Voltage decreases
In a step-up transformer, the primary voltage is converted into a higher secondary voltage. The ratio of the primary to secondary windings determines how much the voltage increases, making it suitable for long-distance transmission.
Why are step-down transformers commonly used in power distribution systems?
A Increase current
B Reduce voltage
C Control power flow
D Increase voltage
Step-down transformers are used in power distribution systems to reduce the high transmission voltage to a safer, usable voltage level. This is necessary to supply power to homes and businesses safely without damaging electrical equipment.
What is the main function of voltage regulation in power systems?
A Increase power
B Reduce current
C Maintain voltage levels
D Stabilize frequency
Voltage regulation is crucial to ensure that voltage remains stable despite changes in the load. Proper voltage regulation prevents voltage fluctuations, which can damage electrical equipment or cause inefficiencies in the power system.
How is voltage regulation typically achieved in power systems?
A By using transformers
B By using capacitors
C By controlling power factor
D By using resistors
Voltage regulation is often achieved by adjusting the voltage using transformers. Step-up or step-down transformers can regulate voltage to ensure that it remains within the desired range for efficient and safe power distribution.
What effect does voltage regulation have on power system efficiency?
A Reduces efficiency
B Increases losses
C Improves efficiency
D Decreases stability
Proper voltage regulation improves the efficiency of the power system by maintaining consistent voltage levels. This prevents overvoltage or undervoltage conditions that can reduce the performance of electrical devices and lead to energy wastage.
What determines the voltage increase in a step-up transformer?
A Frequency of supply
B Transformer oil
C Length of conductor
D Number of turns
The voltage increase in a step-up transformer is determined by the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. More turns on the secondary side increase the voltage.
What is the typical use of a step-up transformer in power transmission?
A To increase voltage
B To reduce power loss
C To stabilize frequency
D To step down voltage
Step-up transformers are used in power transmission to increase the voltage before the electricity travels over long distances. High voltage reduces current, which minimizes power losses due to resistance in the transmission lines.
What would happen if the primary voltage of a step-down transformer is lower than the secondary voltage?
A Current increases
B Voltage increases
C Voltage decreases
D Power loss increases
In a step-down transformer, the secondary voltage is lower than the primary voltage. If the primary voltage were lower than the secondary, it would create an inversion, causing the voltage to increase, which is not typical for step-down applications.
Which of the following is crucial for determining the efficiency of a transformer?
A Transformer type
B Frequency
C Voltage ratio
D Load size
The efficiency of a transformer is largely determined by the voltage ratio between the primary and secondary windings. A higher voltage ratio typically leads to lower losses and more efficient energy transfer between the circuits.
What is the primary cause of voltage fluctuations in power systems?
A Transformer malfunction
B Faults in conductors
C Overload protection
D Change in load
Voltage fluctuations in power systems are primarily caused by changes in load. As the demand for electricity increases or decreases, it can cause voltage instability. Proper voltage regulation helps mitigate these fluctuations.
What is the most significant factor affecting the performance of step-up transformers?
A Core material
B Temperature
C Efficiency of insulation
D Load demand
The core material of a step-up transformer significantly affects its performance. The core needs to have high magnetic permeability to efficiently transfer magnetic flux from the primary to the secondary coil, minimizing energy loss and improving efficiency.
What kind of power loss occurs in transformers during operation?
A Transmission loss
B Capacitive loss
C Core loss
D Inductive loss
Core loss, also known as iron loss, occurs in transformers when the magnetic field induces currents in the core material. These currents cause heat generation, leading to energy loss. Core loss is a key factor in transformer efficiency.
Which factor increases the efficiency of step-down transformers?
A Using high resistance conductors
B Reducing turns in secondary coil
C Maintaining high voltage
D Improving insulation
Reducing the number of turns in the secondary coil of a step-down transformer helps decrease the voltage while increasing current to match the load requirements. This improves efficiency, as fewer turns reduce energy loss due to resistance.