Physics
Electrical Machines and Circuits
720 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
C
Correct answer
Explanation
The SI unit of inductance is the Henry (H), named after Joseph Henry. Farad is the unit of capacitance, Ohm is the unit of resistance, and Watt is the unit of power.
D
Correct answer
Explanation
The SI unit of power is the Watt (W), named after James Watt. Volt is the unit of electric potential, Ohm is the unit of resistance, and Coulomb is the unit of electric charge.
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1500 V DC
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1500 V AC
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25000 V AC
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25000 V DC
A,C
Correct answer
Explanation
Indian Railways uses dual traction systems - 1500V DC for Mumbai's suburban network (Western and Central lines) and 25000V AC for mainline electrification.
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Fuse
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Main Board
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Neighbour's House
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Bulb
C
Correct answer
Explanation
When encountering a power failure, the standard troubleshooting sequence is: first check if neighbours have power (to determine if it's a grid-wide issue or isolated to your home), then check your main switch/fuse box. Checking neighbours first helps quickly diagnose whether to call the utility company or check your internal wiring. This is a practical home maintenance question.
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200-250
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300-350
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400-650
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500-550
C
Correct answer
Explanation
The Electrophorus electricus (electric eel) can generate discharge voltages ranging from 400 to 650 volts. This high-voltage shock is used for both hunting prey and self-defense. Lower ranges like 200-250 are insufficient for the maximum capacity of a mature specimen.
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100-150
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200-250
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400-650
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300-350
C
Correct answer
Explanation
Electric eels (Electrophorus electricus) are capable of generating electric shocks up to 600-860 volts, with 400-650V being the most accurate range among the options. The lower ranges (100-150V, 200-250V) severely underestimate their power, while 300-350V is still below their maximum documented capacity.
A
Correct answer
Explanation
DC (Direct Current) power supply has zero frequency because the current flows in one direction only and does not alternate periodically like AC (Alternating Current).
A
Correct answer
Explanation
DC (Direct Current) power supply has zero frequency because the current flows in one direction only and does not alternate periodically like AC (Alternating Current). This is a duplicate of entry 72364.
A
Correct answer
Explanation
DC (Direct Current) power supply has zero frequency because the current flows in one direction only, unlike AC (Alternating Current) which periodically reverses direction. Frequency is the number of cycles per second, and DC has no oscillation or cycles.
A
Correct answer
Explanation
DC (Direct Current) power supply has zero frequency because the current flows in one direction only, unlike AC (Alternating Current) which periodically reverses direction. Frequency is the number of cycles per second, and DC has no oscillation or cycles.
A
Correct answer
Explanation
DC (Direct Current) power supply has zero frequency because the current flows in one direction only, unlike AC (Alternating Current) which periodically reverses direction. Frequency is the number of cycles per second, and DC has no oscillation or cycles.
A
Correct answer
Explanation
DC power supply provides direct current which flows in one direction without changing direction or magnitude periodically. Unlike AC (alternating current) which oscillates and has frequency, DC has zero frequency.
B
Correct answer
Explanation
In India, the standard residential voltage level is 230V as per Indian standards. Option B (240V) is approximately correct and commonly used in many countries. 415V is typically used for 3-phase industrial supply.
A
Correct answer
Explanation
Residential apartments can have either single-phase (1 phase) or three-phase (3 phase) power supply depending on the building's electrical design and load requirements. Three-phase is common in larger apartments while single-phase is typical for smaller units.
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Power Capacitors
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Regulators
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Voltage stabilizers
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Current stabilizers
C
Correct answer
Explanation
Voltage stabilizers are designed to manage power fluctuations by maintaining a constant output voltage despite variations in input voltage. Regulators and capacitors serve different purposes, while 'current stabilizers' is not a standard term.