Q. Faraday's law of electromagnetic induction states that the induced EMF in a circuit is proportional to what? (2019)
A.
Rate of change of current
B.
Rate of change of magnetic flux
C.
Rate of change of resistance
D.
Rate of change of voltage
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Solution
Faraday's law states that the induced EMF is proportional to the rate of change of magnetic flux.
Correct Answer:
B
— Rate of change of magnetic flux
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Q. If the magnetic flux through a coil changes from 0.5 Wb to 0.2 Wb in 2 seconds, what is the average induced emf? (2023)
A.
150 V
B.
100 V
C.
75 V
D.
50 V
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Solution
Average induced emf = -ΔΦ/Δt = -(0.2 - 0.5)/2 = 0.15 V = 150 V.
Correct Answer:
B
— 100 V
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Q. If the magnetic flux through a coil changes, what happens to the induced EMF? (2023)
A.
It remains constant
B.
It increases
C.
It decreases
D.
It is induced
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Solution
An induced EMF is generated when there is a change in magnetic flux through a coil.
Correct Answer:
D
— It is induced
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Q. In a circuit with an inductor, what happens to the current when the voltage is suddenly increased? (2020)
A.
Increases immediately
B.
Decreases immediately
C.
Increases gradually
D.
Decreases gradually
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Solution
In a circuit with an inductor, the current increases gradually due to the inductor's opposition to changes in current.
Correct Answer:
C
— Increases gradually
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Q. In a series RLC circuit, what happens to the impedance at resonance? (2021)
A.
Minimum
B.
Maximum
C.
Zero
D.
Infinite
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Solution
At resonance in a series RLC circuit, the impedance is at a minimum.
Correct Answer:
A
— Minimum
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Q. In a transformer, if the primary coil has 100 turns and the secondary coil has 200 turns, what is the turns ratio? (2021)
A.
1:2
B.
2:1
C.
1:1
D.
3:1
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Solution
The turns ratio is 100:200, which simplifies to 1:2.
Correct Answer:
A
— 1:2
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Q. In a transformer, if the primary coil has 100 turns and the secondary coil has 50 turns, what is the turns ratio? (2023)
A.
2:1
B.
1:2
C.
1:1
D.
3:1
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Solution
The turns ratio is 2:1, as the primary has twice the number of turns compared to the secondary.
Correct Answer:
A
— 2:1
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Q. In a transformer, if the primary coil has more turns than the secondary coil, what type of transformer is it? (2021)
A.
Step-up transformer
B.
Step-down transformer
C.
Isolation transformer
D.
Auto transformer
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Solution
If the primary coil has more turns than the secondary coil, it is a step-down transformer.
Correct Answer:
B
— Step-down transformer
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Q. In an AC circuit, the current lags behind the voltage by 90 degrees in which component? (2020)
A.
Resistor
B.
Capacitor
C.
Inductor
D.
Transformer
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Solution
In an inductor, the current lags behind the voltage by 90 degrees.
Correct Answer:
C
— Inductor
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Q. In an AC circuit, the current lags behind the voltage by 90 degrees in which type of circuit? (2020)
A.
Resistive
B.
Inductive
C.
Capacitive
D.
RLC
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Solution
In an inductive circuit, the current lags behind the voltage by 90 degrees.
Correct Answer:
B
— Inductive
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Q. In an AC circuit, the current lags the voltage by 90 degrees in which of the following components? (2020)
A.
Resistor
B.
Capacitor
C.
Inductor
D.
Transformer
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Solution
In an inductor, the current lags the voltage by 90 degrees.
Correct Answer:
C
— Inductor
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Q. In an AC circuit, the current lags the voltage by 90 degrees in which type of circuit? (2020)
A.
Resistive
B.
Capacitive
C.
Inductive
D.
RLC
Show solution
Solution
In an inductive circuit, the current lags the voltage by 90 degrees.
Correct Answer:
C
— Inductive
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Q. In an AC circuit, what is the phase difference between voltage and current in a purely inductive circuit? (2021)
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
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Solution
In a purely inductive AC circuit, the current lags the voltage by 90 degrees.
Correct Answer:
B
— 90 degrees
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Q. In an RLC circuit, what does the term 'resonance' refer to? (2019)
A.
Maximum current at a specific frequency
B.
Minimum current at any frequency
C.
Constant voltage
D.
Zero inductance
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Solution
Resonance in an RLC circuit occurs when the inductive reactance equals the capacitive reactance, resulting in maximum current at a specific frequency.
Correct Answer:
A
— Maximum current at a specific frequency
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Q. In an RLC circuit, what happens to the impedance at resonance? (2023)
A.
Minimum
B.
Maximum
C.
Zero
D.
Infinite
Show solution
Solution
At resonance, the impedance in an RLC circuit is at a minimum.
Correct Answer:
A
— Minimum
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Q. In an RLC circuit, what happens to the impedance when the circuit is at resonance? (2023)
A.
Minimum
B.
Maximum
C.
Zero
D.
Infinite
Show solution
Solution
At resonance, the impedance of an RLC circuit is at its minimum.
Correct Answer:
A
— Minimum
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Q. In an RLC series circuit, what happens to the impedance at resonance? (2020)
A.
It is minimum
B.
It is maximum
C.
It is zero
D.
It is equal to resistance
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Solution
At resonance in an RLC series circuit, the impedance is equal to the resistance.
Correct Answer:
D
— It is equal to resistance
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Q. The phenomenon of electromagnetic induction was discovered by which scientist? (2022)
A.
Michael Faraday
B.
James Clerk Maxwell
C.
Nikola Tesla
D.
Albert Einstein
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Solution
Electromagnetic induction was discovered by Michael Faraday.
Correct Answer:
A
— Michael Faraday
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Q. The self-inductance of a coil depends on which of the following factors? (2021)
A.
Number of turns
B.
Area of cross-section
C.
Length of the coil
D.
All of the above
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Solution
The self-inductance of a coil depends on the number of turns, area of cross-section, and length of the coil.
Correct Answer:
D
— All of the above
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Q. What happens to the induced EMF if the speed of the magnet moving through a coil is doubled? (2022)
A.
It remains the same
B.
It doubles
C.
It halves
D.
It quadruples
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Solution
The induced EMF doubles if the speed of the magnet moving through the coil is doubled.
Correct Answer:
B
— It doubles
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Q. What happens to the induced emf when the rate of change of magnetic flux increases? (2019)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
Show solution
Solution
The induced emf increases when the rate of change of magnetic flux increases, according to Faraday's Law.
Correct Answer:
A
— Increases
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Q. What is the effect of frequency on the inductive reactance? (2023)
A.
Directly proportional
B.
Inversely proportional
C.
No effect
D.
Depends on the resistance
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Solution
Inductive reactance is directly proportional to frequency; as frequency increases, inductive reactance increases.
Correct Answer:
A
— Directly proportional
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Q. What is the effect of increasing the frequency of AC on the inductive reactance? (2021)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
Inductive reactance increases with the frequency of AC.
Correct Answer:
A
— Increases
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Q. What is the effect of increasing the frequency of an AC source on the inductive reactance? (2023)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
Increasing the frequency of an AC source increases the inductive reactance.
Correct Answer:
A
— Increases
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Q. What is the effect of increasing the frequency of the AC supply on the inductive reactance? (2020)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
Inductive reactance increases with frequency, as X_L = 2πfL.
Correct Answer:
A
— Increases
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Q. What is the effect of increasing the number of turns in a coil on its inductance? (2023)
A.
Increases inductance
B.
Decreases inductance
C.
No effect
D.
Depends on the material
Show solution
Solution
Increasing the number of turns in a coil increases its inductance.
Correct Answer:
A
— Increases inductance
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Q. What is the formula for calculating the induced EMF in a coil? (2023)
A.
E = -dΦ/dt
B.
E = R * I
C.
E = V * I
D.
E = L * di/dt
Show solution
Solution
The induced EMF in a coil is given by the formula E = -dΦ/dt, where Φ is the magnetic flux.
Correct Answer:
A
— E = -dΦ/dt
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Q. What is the formula for the inductive reactance (X_L) in an AC circuit? (2022)
A.
X_L = 2πfL
B.
X_L = R/L
C.
X_L = 1/(2πfC)
D.
X_L = V/I
Show solution
Solution
The formula for inductive reactance is X_L = 2πfL, where f is the frequency and L is the inductance.
Correct Answer:
A
— X_L = 2πfL
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Q. What is the main purpose of a choke in an AC circuit? (2022)
A.
To increase current
B.
To decrease current
C.
To store energy
D.
To convert AC to DC
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Solution
A choke is used to decrease current in an AC circuit by providing inductive reactance.
Correct Answer:
B
— To decrease current
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Q. What is the primary factor that determines the inductance of a coil? (2020)
A.
Length of the wire
B.
Number of turns
C.
Material of the core
D.
All of the above
Show solution
Solution
The inductance of a coil is determined by the length of the wire, the number of turns, and the material of the core.
Correct Answer:
D
— All of the above
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Showing 1 to 30 of 44 (2 Pages)
EMI & AC - Electromagnetic Induction MCQ & Objective Questions
Understanding "EMI & AC - Electromagnetic Induction" is crucial for students preparing for school and competitive exams in India. This topic not only forms a significant part of the physics syllabus but also features prominently in various objective questions and MCQs. Practicing these MCQs helps students enhance their conceptual clarity and boosts their confidence, leading to better exam scores.
What You Will Practise Here
Fundamentals of Electromagnetic Induction
Faraday's Law of Induction and its applications
AC Circuits: Concepts and Characteristics
Key formulas related to inductance and capacitance
Understanding Lenz's Law and its implications
Diagrams illustrating electromagnetic principles
Real-world applications of EMI in technology
Exam Relevance
The topic of "EMI & AC - Electromagnetic Induction" is frequently tested in CBSE, State Boards, NEET, and JEE exams. Students can expect questions that assess their understanding of fundamental concepts, calculations involving formulas, and application-based scenarios. Common question patterns include numerical problems, conceptual questions, and diagram-based queries that require a thorough grasp of the subject.
Common Mistakes Students Make
Confusing the direction of induced current as per Lenz's Law.
Misapplying Faraday's Law in numerical problems.
Overlooking the significance of phase difference in AC circuits.
Failing to interpret diagrams correctly, leading to incorrect answers.
FAQs
Question: What is the significance of Faraday's Law in EMI?Answer: Faraday's Law states that the induced electromotive force in a circuit is directly proportional to the rate of change of magnetic flux through the circuit, which is fundamental in understanding electromagnetic induction.
Question: How do AC circuits differ from DC circuits?Answer: AC circuits involve alternating current, which changes direction periodically, while DC circuits involve direct current that flows in one direction. This difference affects how energy is transmitted and used in various applications.
Now is the time to strengthen your understanding of "EMI & AC - Electromagnetic Induction." Dive into our practice MCQs and test your knowledge to excel in your exams!
