Transformer Basics Quiz

What is the purpose of a step-down transformer?

• To increase voltage for power transmission

• To provide extra-low voltage for small appliances

• To convert AC to DC

• To stabilize voltage fluctuations

Answer explanation

A step-down transformer reduces high voltage to a lower voltage suitable for small appliances, ensuring safe and efficient operation. This makes 'To provide extra-low voltage for small appliances' the correct choice.

What is the maximum voltage a large step-up transformer can produce for power transmission?

• 100 kV

• 200 kV

• 300 kV

• 400 kV

Answer explanation

A large step-up transformer can produce high voltages for efficient power transmission. Among the options, 400 kV is the maximum voltage typically achievable, making it the correct choice.

What is the role of a transformer in an electrical circuit?

• To generate electricity

• To change supply voltages

• To store electricity

• To convert electricity to light

Answer explanation

A transformer is used in electrical circuits to change supply voltages, allowing for efficient transmission and distribution of electricity. It does not generate, store, or convert electricity to light.

What is one reason why AC has been adopted for mains electricity supplies?

• It is less efficient than DC.

• It is more economical to transmit electricity over long distances at high voltage.

• It requires more maintenance.

• It is easier to generate.

Answer explanation

AC is preferred for mains electricity because it can be transmitted over long distances more economically at high voltages, reducing energy loss. This makes it more efficient for widespread distribution compared to DC.

What does the secondary winding in a transformer do?

• It generates electricity.

• It carries the secondary current and voltage.

• It reduces the magnetic flux.

• It increases the primary voltage.

Answer explanation

The secondary winding in a transformer carries the secondary current and voltage, allowing it to deliver power to the load. This is its primary function, distinguishing it from other options that do not accurately describe its role.

What is a benefit of having no moving parts in transformers?

• Increased complexity.

• Higher maintenance costs.

• Reduced maintenance requirements.

• Lower efficiency.

Answer explanation

Having no moving parts in transformers leads to reduced maintenance requirements, as there are fewer components that can wear out or fail, resulting in a more reliable and efficient operation.

What is the purpose of electrical transformers?

• To provide electric shock protection

• To convert electrical energy for different uses and purposes

• To increase voltage only

• To decrease voltage only

Answer explanation

The correct choice is 'To convert electrical energy for different uses and purposes' because transformers can both increase and decrease voltage, allowing for efficient energy distribution and adaptation to various applications.

What type of current transformers are required for metering?

• Class A CTs

• Class B CTs

• Class X CTs

• Class Y CTs

Answer explanation

Class X CTs are specifically designed for metering applications, providing high accuracy and stability over a wide range of currents, making them the ideal choice for accurate measurement in electrical systems.

What size meter is needed if the CT has a ratio of 1360:5 and the primary current is 800 A?

• 2.94 A

• 3.94 A

• 4.94 A

• 5.94 A

Answer explanation

To find the secondary current, use the formula: I_secondary = (I_primary * CT_ratio_secondary) / CT_ratio_primary. Here, I_secondary = (800 A * 5) / 1360 = 2.94 A. Thus, the correct meter size is 2.94 A.

Why is it important to ensure the primary and secondary circuits are efficiently coupled?

• To reduce energy consumption

• To give an accurate reading

• To increase voltage

• To decrease current

Answer explanation

Efficient coupling of primary and secondary circuits is crucial for accurate readings. If the circuits are not well-coupled, it can lead to measurement errors, affecting the reliability of the data collected.