Electromagnetic Waves Practice Questions
Class 12 · Physics · 2877 free MCQs with instant results and detailed explanations.
2877
Total
941
Easy
1414
Medium
522
Hard
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Topics in Electromagnetic Waves
Displacement Current
914
Properties of EM Waves
1027
EM Spectrum
936
Sample Questions from Electromagnetic Waves
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
What is the physical significance of displacement current in electromagnetism?
A.
It accounts for changing electric fields.
B.
It is only relevant in static electric fields.
C.
It cancels out magnetic fields.
D.
It only exists in conductive materials.
Show Answer & Explanation
Correct Answer: A
Displacement current is crucial for explaining how a changing electric field can produce a magnetic field, especially in scenarios like capacitors.
Q2
Easy
Which of the following equations represents the displacement current?
A.
Id = ฮต0 (dฮฆE/dt)
B.
Id = ฮผ0 (dฮฆB/dt)
C.
Id = Q/t
D.
Id = I + ฮต0 (dฮฆE/dt)
Show Answer & Explanation
Correct Answer: A
The displacement current is defined as Id = ฮต0 (dฮฆE/dt), where dฮฆE is the change in electric flux.
Q3
Easy
In a parallel plate capacitor, what happens to the displacement current as the electric field increases?
A.
It decreases.
B.
It remains constant.
C.
It increases.
D.
It becomes zero.
Show Answer & Explanation
Correct Answer: C
As the electric field increases, the rate of change of electric flux increases, hence the displacement current increases.
Q4
Medium
What is the primary role of displacement current in Maxwell's equations?
A.
To account for changing electric fields
B.
To measure conduction current
C.
To generate magnetic fields
D.
To define electric potential
Show Answer & Explanation
Correct Answer: A
Displacement current is essential in explaining how changing electric fields can produce magnetic fields, completing Maxwell's equations.
Q5
Medium
In a capacitor, if the electric field between the plates increases, what happens to the displacement current?
A.
It decreases
B.
It stays constant
C.
It increases
D.
It becomes zero
Show Answer & Explanation
Correct Answer: C
The displacement current is proportional to the rate of change of the electric field. An increasing electric field means an increasing displacement current.
Q6
Medium
If the area of a capacitor plate is doubled while keeping the voltage constant, how does the displacement current change?
A.
It halves
B.
It doubles
C.
It remains the same
D.
It quadruples
Show Answer & Explanation
Correct Answer: B
Doubling the area increases the displacement current because it is directly proportional to the area of the plates.
Q7
Medium
Which of the following statements about displacement current is true?
A.
It can exist in a vacuum.
B.
It only occurs in conductors.
C.
It is dependent on temperature.
D.
It is the same as conduction current.
Show Answer & Explanation
Correct Answer: A
Displacement current can exist in regions where there is no actual conduction current, such as in a vacuum with changing electric fields.
Q8
Hard
What is the primary role of displacement current in Maxwell's equations?
A.
To account for changes in electric field in empty space
B.
To replace the need for a magnetic field
C.
To ensure that electric field lines do not cross
D.
To eliminate the concept of electric charge
Show Answer & Explanation
Correct Answer: A
Displacement current is introduced in Maxwell's equations to account for changing electric fields in regions where there is no conduction current.
Q9
Hard
If the electric field between two capacitor plates changes at a rate of 5 V/mยทs, what is the displacement current density, given the permittivity of free space is 8.85 ร 10^-12 F/m?
A.
4.425 ร 10^-11 A/mยฒ
B.
1.77 ร 10^-11 A/mยฒ
C.
2.95 ร 10^-10 A/mยฒ
D.
7.77 ร 10^-12 A/mยฒ
Show Answer & Explanation
Correct Answer: A
The displacement current density can be calculated using the formula J_d = ฮต * (dE/dt), where ฮต is the permittivity and dE/dt is the rate of change of electric field.
Q10
Hard
In a region of free space, if the electric field is increasing at a rate of 10^2 V/mยทs, what is the value of the displacement current in a 1 mยฒ area?
A.
8.85 ร 10^-10 A
B.
3.54 ร 10^-10 A
C.
1.77 ร 10^-10 A
D.
17.7 ร 10^-10 A
Show Answer & Explanation
Correct Answer: A
Displacement current can be calculated using I_d = ฮตโ * (dE/dt) * A, where dE/dt is the rate of change of electric field.
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Electromagnetic Waves โ Class 12 Physics Practice Questions Online
This page contains 2877 practice MCQs for the chapter Electromagnetic Waves in Class 12 Physics. The questions are organized by difficulty โ 941 easy, 1414 medium, 522 hard โ so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit. This chapter covers 3 topics, giving you comprehensive coverage of the entire chapter.