Physics

Electrical Machines and Circuits

754 Questions

Electrical machines and circuits involve the principles of alternating and direct current, transformers, diodes, and power consumption. These concepts are essential for engineering and technical exams. Review these practice questions to test your knowledge of circuit analysis.

Transformers and impedanceAlternating and direct currentCircuit components and diodesPower consumption calculations

Electrical Machines and Circuits Questions

Multiple choice

One should not connect a number of electric appliances to the same power sockets because

  1. this can damage the appliances

  2. this can damage the domestic wiring due to over-heating

  3. the appliances will not get full voltage

  4. the appliances will not get proper current
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Connecting multiple appliances to one socket draws excessive current through the same wiring, causing overheating due to resistance. This heat can damage insulation, cause fires, or burn out wiring. The appliances themselves aren't damaged, and voltage drop is less critical than thermal safety.

Multiple choice

Which of the following has only one path for current to follow?

  1. A parallel circuit

  2. An electric circuit

  3. A magnetic pole

  4. A series circuit

  5. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a series circuit, devices are connected so these is only one closed path for current to flow if any part of this path is broken, current will no larger flow in the circuit.

Multiple choice

Household circuits are connected in ____________ and fuse is connected in __________ with an electrical circuit.

  1. series, parallel

  2. series, series

  3. parallel, parallel

  4. parallel, series

  5. -
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the correct answer. Household circuits are connected in parallel because if there is any problem in the circuit, it will not affect the rest of the circuit. Fuses are connected in series because as soon as the current in the circuit exceeds the maximum value, the fuse wire will melt and prevent fire.

Multiple choice

Which of the following will not cause overload in a circuit?

  1. Too many appliances connected to one electrical socket

  2. Current flowing equals the capacity of components

  3. Fuse of high capacity connected with low capacity components

  4. When loose and corroded wires are connected in a circuit

  5. -
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct answer. This prevents overloading in circuit because current drawn is equal to the maximum capacity of the components.

Multiple choice

Which of the following appliances, when connected to a circuit, will melt the fuse and break the circuit?

  1. An electric oven of 0.6 kW operated at 220 V having a current rating of 5 A

  2. An electric oven of 2 kW operated at 220 V having a current rating of 6 A

  3. An electric oven of 0.8 kW operated at 200 V having a current rating of 5 A

  4. An electric oven of 1 kW operated at 200 V having a current rating of 6 A

  5. -
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct answer. Current drawn by the electric oven, I = P/V = 2000/220 = 9 A. The current exceeds the safe limit of the circuit and hence, the fuse will melt.

Multiple choice

Consider the following statements regarding AC to DC power supply: (a) An AC to DC power supply is built using a transformer and a half-wave rectifier (b) Transformer is used to step down the voltage i/p (c) Rectifier converts AC to pulsed DC Which of the above statements is/are true?

  1. Only (a) and (c)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All of the above

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement (a) is false: An AC to DC power supply is built using a transformer and a full-wave rectifier. Statement (b) is true: Transformer is used to step down the voltage i/p. Statement(c) is true: Rectifier converts AC to pulsed DC.

Multiple choice

Consider the following statements regarding 7-Segment LED Display. (a) Used for displaying numbers only (b) 8 individual LEDs are used to make up the display (c) When a voltage is applied across one of the LEDs, a portion of the 7 lights up Which of the above statements is/are false?

  1. Only (a)

  2. Only (b)

  3. Only (c)

  4. All of the above

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement (a) is false. Used for displaying numbers and other characters. Statement (b) is false. 7 individual LEDs are used to make up the display. Statement (c) is false. When a voltage is applied across one of the LEDs, a portion of the 8 lights up.

Multiple choice

Consider the following statements:

  1. Transformer is used to transform low voltage supply to medium voltage supply.
  2. Battery is used to safeguard against short circuit.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1 is incorrect. The transformer is used to transform a medium voltage supply to a low voltage supply. Statement 2 is also incorrect. A battery is used to measure the voltage potential.