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

Which of the following acts as a circuit breaker?

  1. Fuse

  2. Switch

  3. Resettable protective device

  4. Voltmeter

  5. Resistor
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is an electronic switch which protects a circuit from the damage caused by overload or short circuit. Option 3 is incorrect.

Multiple choice

In a DC arc welding operation, the voltage arc length characteristics was obtained as Varc = 20 + 5l where the arc length l was varied between 5 mm and 7 mm. Here, Varc denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristics, the open circuit voltage and the short circuit current for the welding operation are

  1. 45 V, 450 A

  2. 75 V, 750 A

  3. 95 V, 950 A

  4. 150 V, 1500 A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Why is electric power transmitted over long distances at high voltage?

  1. To minimize power loses due to Joule's heating

  2. To maximize power loses due to Joule's heating

  3. To balance power loses due to Joule's heating

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For constant electric power, higher the voltage, lower is the current (as $P=IV$) through the wire. As power loss due to Joule's heating is proportional to $I^2$, for a small current, power loss is also small. So, power is transmitted over long distances at high voltage to minimize power loses due to Joule's heating.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

The operating temperature of the filament of lamp is ${ 2000 }^{ 0 }C$. The temperature coefficient of the material of filament is ${ 0.005 }^{ 0 }{ C }^{ -1 }$. If the atmospheric temperature is ${ { 0 }^{ 0 }C }$, then the current in the 100W-200W lamp when it is switched on is nearest to 

  1. 2.5 A

  2. 3.5 A

  3. 4.5 A

  4. 5.5 A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The resistance of the filament varies with temperature. At operating temperature (2000°C), R_hot = V²/P = 220²/100 = 484Ω. Using the temperature coefficient formula: R_cold = R_hot/(1 + α(2000-0)) = 484/(1 + 0.005×2000) = 484/11 = 44Ω. Initial current = V/R_cold = 220/44 = 5A. However, this is an approximation - the actual surge current depends on how quickly the filament heats up. Given the options, 4.5A is the closest reasonable estimate.

Multiple choice physics current electricity and magnetism electric cells and batteries

When two batteries are connected in series the voltage in the circuit will _____________ .

  1. increase

  2. decrease

  3. remains same

  4. first decrease than increase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a series connection the positive terminal of the first battery is connected to the negative terminal of the second battery.

And the Equivalent voltage of the battery is the sum of the voltage of individual cell.So, when two batteries are connected in series the voltage in the circuit will increases.
Therefore, A is correct option.

Multiple choice

Electricity cannot flow unless there is what?

  1. amperes

  2. ohms

  3. watts

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

Voltage (potential difference) is the force or pressure that pushes electrons through a conductor. Without voltage, there is no flow of electricity.

Multiple choice

Which two currents are involved with the blend?

  1. galvanic & DC

  2. high frequency & shortwave

  3. high frequency & galvanic

  4. electrolysis & galvanic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The blend modality in electrolysis combines high frequency (thermolysis) and galvanic (direct current) to destroy the hair follicle. This synergy allows for faster and more effective treatment.

Multiple choice

Which of the following is used as a “ground”?

  1. single prong plug

  2. 2 prong plug

  3. 3 prong plug

  4. 4 prong plug
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A 3-prong plug includes a ground pin, which provides a path for electrical current to safely return to the earth in the event of a short circuit.

Multiple choice the operational amplifier (op-amp) electronics physics properties of an ideal op-amp

Which among the following are the major responsible reasons for the cause of 'Slew Rate'?

  1. Current limiting

  2. Saturation of internal stages due to application of high frequency & amplitude signal

  3. Both a & b

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Slew rate is limited by the internal current available to charge compensation capacitors and the saturation of internal stages when driven by high-frequency or high-amplitude signals.

Multiple choice physics chemical effects of electric current study about cells electric cell types of cells

Why the bulb brighter in a simple circuit that has more cells?

  1. Because the flow of electricity is more

  2. Because the flow of electricity is same

  3. Because the flow of electricity is less

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Adding more cells in series increases the total voltage of the circuit, which increases the current flowing through the bulb, making it brighter.