Electrical Science - Transformers

Multiple Choice

Three Transformers are labeled in the image. which statement can be true?

•   Transformer 1 will step up the voltage and Transformers 2 and 3 will step down the voltage
  

•  Transformers 2 and 3 will step up the voltage and Transformer 1 will step down the voltage

  
  

•  Transformer 3 will step up the voltage and Transformers 1 and 2 will step down the voltage

  
  

•  Transformer 1 and 2 will step up the voltage, and Transformer 3 will step down the voltage

  
  

Multiple Choice

Which activity will produce the highest current?

• Move the magnet bar into the coil while the coil remains stationery

• Move the coil into the magnet bar while the magnet remains stationery

• Move the coil and magnet towards each other

• Move the coil and magnet away from each other

Multiple Choice

What is the formula for induced emf in a self-inductance circuit?

• Induced emf = -L(I2 - I1)/t

• Induced emf = L(I1 + I2)/t

• Induced emf = L(I1 - I2)/t

• Induced emf = L(I1 * I2)/t

Multiple Choice

If the frequency of the AC voltage across an inductor is doubled, the inductive reactance of that inductor

• increases to 4 times its original value.

• increases to twice its original value.

• decreases to one-half its original value.

• decreases to one-fourth its original value.

Multiple Choice

Which of the following gives the direction of the induced e.m.f.?

• Faraday’s law

• Lenz’s law

• Ampere

• Biot-Savart’s law.

Multiple Choice

If the current flowing through a coil of inductance of 0.7H increases from 2A to 10A in 40 mS, calculate the average value of an induced emf.

• -140V

• 5.6V

• 0.7V

• 8V

Multiple Choice

What are the main components of a standard transformer as shown in the diagram?

• Supply

• Primary Winding

• Secondary Winding

• Laminated Steel Core

Multiple Choice

What is the relationship between primary voltage, secondary voltage, primary current, and secondary current in a transformer?

• Primary voltage is greater than secondary voltage

• Primary current is equal to secondary current

• Primary voltage is equal to secondary voltage

• Primary current is greater than secondary current

Multiple Choice

A transformer connected to a 230 volt 50Hz supply has a primary winding of 1200 turns. Calculate the emf induced in a secondary winding of 300 turns.

• 57.5V

• 120V

• 230V

• 300V

Multiple Choice

A transformer connected to a 230 volt 50Hz supply has a primary winding of 1200 turns. Calculate the number of turns that would be required in the secondary winding, if it is to produce an emf of 100 volts.

• 522 turns

• 1200 turns

• 1000 turns

• 230 turns

Multiple Choice

A transformer connected to a 230 volt 50Hz supply has a primary winding of 1200 turns. Calculate the volts per turn there are on the primary and secondary windings.

• 0.19 volts

• 0.57 volts

• 1.19 volts

• 0.95 volts

Multiple Choice

What is the formula to calculate kVA in terms of volts and amps?

• kVA = Amps / Volts

• kVA = Volts × Amps

• kVA = Amps × Volts

• kVA = Volts + Amps

Multiple Choice

Which component of a transformer does not actually make contact with the electrical energy but plays a crucial role in its operation?

• Primary winding

• Secondary winding

• Magnetic core

• Cooling system

Multiple Choice

What is the principle by which transformers operate?

• Electromagnetic induction

• Thermal induction

• Piezoelectric effect

• Capacitive coupling

Multiple Choice

What is the primary voltage of the voltage transformer shown in the diagram?

• 110V

• 11kV

• 220V

• 5kV

Multiple Choice

What are the advantages of using instrument transformers?

• Simplifies insulation of measuring instruments

• Isolates instrument from main circuit

• Allows remote reading of measuring instruments

• Standardizes voltage or current

Multiple Choice

An electrical contractor wishes to monitor a 660V supply with a standard 110V voltmeter. Determine the turns ratio of the VT to perform this task.

• 6:1

• 5:1

• 4:1

• 3:1

Multiple Choice

What is the purpose of a current transformer (CT) as shown in the diagram?

• To measure voltage

• To measure current

• To convert AC to DC

• To increase voltage

Multiple Choice

An ammeter having a full scale deflection of 5A is used to measure a line current of 200A. If the primary is wound with two turns, calculate the number of secondary turns required to give full scale deflection.

• 40 turns

• 60 turns

• 80 turns

• 100 turns

Multiple Choice

What is the importance of ensuring that a Current Transformer is always connected on the secondary side?

• To prevent large voltage discharge

• To measure current accurately

• To maintain circuit integrity

• To reduce energy loss

Multiple Choice

What is the purpose of an isolating transformer?

• To connect two circuits directly

• To separate electrical circuits

• To increase voltage

• To decrease voltage

Open Ended

Any questions?

Poll

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