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Previous Year Questions

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9,374 Questions
CBSE
#1 Class 12 Physics Electromagnetic Waves 2020 Short 2M
An electromagnetic wave passing through vacuum is described by $E = E_0\sin(kx - \omega t)$ and $B = B_0\sin(kx - \omega t)$. Write the relations between $E_0$, $B_0$, $k$, $\omega$ and $c$.
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CBSE
#2 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M
Which of the following electromagnetic waves has the minimum frequency?
A. radio waves
B. ultrasonic waves
C. audible waves
D. microwaves
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CBSE
#3 Class 12 Physics Electromagnetic Waves 2021 Mcq 1M
An electromagnetic wave of frequency 3 MHz passes from vacuum into a medium with dielectric constant $k = 4$. Then
A. both wavelength and frequency remain unchanged
B. wavelength is doubled and frequency becomes half
C. wavelength is halved and frequency remains unchanged
D. wavelength is doubled and frequency remains unchanged
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CBSE
#4 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M
Which radiation in sunlight causes the heating effect?
A. ultraviolet
B. infrared
C. visible light
D. all of these
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CBSE
#5 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M
Which of the following is/are NOT electromagnetic waves?
A. $\beta$-rays
B. X-rays
C. cosmic rays
D. both (a) and (b)
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CBSE
#6 Class 12 Physics Electromagnetic Waves 2018 Mcq 1M
The waves which CANNOT travel in vacuum are
A. X-rays
B. radio waves
C. infrasonic waves
D. ultraviolet waves
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CBSE
#7 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M
According to Maxwell's displacement current law, a changing electric field is the source of
A. an emf
B. magnetic field
C. pressure gradient
D. all of these
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CBSE
#8 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M
The displacement current exists in a region where the electric field
A. increases with time
B. decreases with time
C. attains a constant value
D. both (a) and (b)
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CBSE
#9 Class 12 Physics Electromagnetic Waves 2012 Mcq 1M
The idea of displacement current was introduced by
A. Hertz
B. Ampere
C. Maxwell
D. Faraday
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CBSE
#10 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M
The unit of the ratio of magnetic field $B$ to electric field $E$ ($B/E$) is
A. m s$^{-1}$
B. s m$^{-1}$
C. m s
D. s$^{-2}$
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CBSE
#11 Class 12 Physics Electromagnetic Waves 2021 Short 1M
What is the phase difference between the electric field $\vec{E}$ and magnetic field $\vec{B}$ in an electromagnetic wave propagating in vacuum?
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CBSE
#12 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M
If $\vec{E}$ and $\vec{B}$ represent electric and magnetic field vectors of an electromagnetic wave, the direction of propagation of the wave is along
A. $\vec{E}$
B. $\vec{B}$
C. $\vec{B} \times \vec{E}$
D. $\vec{E} \times \vec{B}$
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CBSE
#13 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M
The electromagnetic waves used to purify water are
A. Infrared rays
B. Ultraviolet rays
C. X-rays
D. Gamma rays
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CBSE
#14 Class 12 Physics Alternating Current 2023 Short 3M
A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, find: (a) the voltage across the secondary coil, (b) the current in the primary coil.
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CBSE
#15 Class 12 Physics Alternating Current 2021 Short 2M
A transformer is used to light a 100 W, 110 V lamp from 220 V mains. If the primary current is 0.5 A, find the efficiency of the transformer.
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CBSE
#16 Class 12 Physics Alternating Current 2022 Short 3M
A 220 V input is supplied to a transformer. The output circuit draws a current of 2.0 A at 440 V. If the efficiency of the transformer is 80%, find the current drawn by the primary windings.
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CBSE
#17 Class 12 Physics Alternating Current 2020 Short 2M
The primary winding of a transformer has 500 turns and the secondary has 5000 turns. The primary is connected to AC supply of 20 V, 50 Hz. What will be the output of the secondary?
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CBSE
#18 Class 12 Physics Alternating Current 2021 Short 2M
A step-up transformer operates on a 220 V line and supplies a load of 2 A. The ratio of primary to secondary windings is 1:25. Find the current in the primary.
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CBSE
#19 Class 12 Physics Alternating Current 2020 Short 2M
A resistance $R$ draws power $P$ when connected to an AC source. If an inductance is placed in series with $R$ such that impedance becomes $Z$, what is the power drawn?
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CBSE
#20 Class 12 Physics Alternating Current 2022 Short 2M
The potential differences across resistance, capacitance and inductance are 80 V, 40 V and 100 V respectively in an LCR circuit. Find the power factor of this circuit.
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