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

Voltage is an electrical ____

  1. signal

  2. symbol

  3. code

  4. number
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Voltage levels in an electrical circuit are used to represent binary states, functioning as signals to convey information.

Multiple choice

The function of the choke is to

  1. increase the voltage

  2. give relatively large impedance of alternating current

  3. regulate the voltage

  4. give relatively large impedance of direct current
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Choke blocks higher-frequency alternating current in an electrical circuit while passing signals of much lower frequency and direct current by having an impedance largely determined by reactance. 

Multiple choice

When a fuse is rated 8 A, it means _____________.

  1. it will not work if current is less than 8 A

  2. it has a resistance of 8 W

  3. it will work only if current is 8 A

  4. it will melt if current exceeds 8 A
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

it will melt if current exceeds 8 A

Multiple choice

Alternating current cannot be used in a/an

  1. amplifier

  2. galvanometer

  3. transformer

  4. voltmeter
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A standard galvanometer is designed to measure direct current (DC). Using alternating current (AC) would cause the needle to oscillate rapidly around zero due to the changing direction of current, resulting in no net deflection.

Multiple choice

Directions: Read the following information and answer the given question.

Riya and Shyna are two siblings. Whenever Riya steps out of her room, she switches off the tubelights and fans whereas Shyna never cares for such things. Her mom always tells them to use electricity judiciously, but Shyna never follows her instruction. 

Why do we need to use electricity judiciously?

  1. It is a precious resource.

  2. It is present in abundance.

  3. It is an inexhaustible natural resource.

  4. It is not a matter of concern at all.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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Multiple choice

Choose a pot that has the greatest possible sensitivity and meets the non linearity requirements of 2 percent (max) from available pots having a thermal rating of 5 watts and resistance ranging from 200 ohm to 5000 ohm in steps of 50 ohm. The output of the pot is to be measured with a device of 4000 ohm input resistance. Determine maximum excitation voltage that can be employed with this pot?

  1. 57 V

  2. 300 V

  3. 100 V

  4. 50 V
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Power rating of pot (P) = 5 watts Load resistance (Rl) = input resistance of measuring device = 4000 ohm Non – linearity to be limited = 2% Maximum possible % non – linearity = 15 (Rt/Rl)2 = 15 (Rt/Rl) Total resistance of the pot = (Rt) = 2/15 Rl = 2/15 x 4000 = 533.3 ohm The pot having maximum value of total resistance, Rt will give greatest sensitivity and that possible resistance with a pot out of the available pots, which will also meet the requirements of 2% (max) non-linearity is 500 ohm Max excitation voltage that can be used with the above pot, (Vimax)2 = PRt = 5 x 500 = 50 V 

Multiple choice

What will happen if you join the two terminals of a 1.5 V pencil cell without connecting them through a switch or a bulb?

  1. The electric cell will catch fire and explode due to large flow of current.

  2. The cell gets drained very fast.

  3. The terminals of the cell get corroded due to large flow of electric current.

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If you join the two terminals of a cell without connecting them through a switch or a bulb, the chemicals in the electric cell will get used up very fast.

Multiple choice

The current across a cross-section of a wire said to be 1 A when

  1. 1 J of work is done in moving a unit charge from one position to another

  2. 1 C of charge flows across the cross-section of the wire per minute

  3. 1 C of charge flows across the cross-section of the wire having a potential difference of 1 volt across it

  4. 1 C of charge flows across the cross-section of the wire per second

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option (4) is correct.

Multiple choice

The power related threats can be avoided using

  1. surge suppressor

  2. line conditioners

  3. UPS

  4. All of the above

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

Power problems arise due to power fluctuations and power failure. Surge suppressor reduces effect of voltage spikes. Line conditioners provide safety against line noise. UPS provides battery backup.