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#1 Class 12 Physics Electromagnetic Waves 2018 Mcq 1M CBSE
The waves which CANNOT travel in vacuum are
A. X-rays
B. radio waves
C. infrasonic waves
D. ultraviolet waves
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#2 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
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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#3 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
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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#4 Class 12 Physics Electromagnetic Waves 2012 Mcq 1M CBSE
The idea of displacement current was introduced by
A. Hertz
B. Ampere
C. Maxwell
D. Faraday
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#5 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
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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#6 Class 12 Physics Electromagnetic Waves 2021 Short 1M CBSE
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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#7 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
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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#8 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
The electromagnetic waves used to purify water are
A. Infrared rays
B. Ultraviolet rays
C. X-rays
D. Gamma rays
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#9 Class 12 Physics Alternating Current 2023 Short 3M CBSE
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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#10 Class 12 Physics Alternating Current 2021 Short 2M CBSE
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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#11 Class 12 Physics Alternating Current 2022 Short 3M CBSE
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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#12 Class 12 Physics Alternating Current 2020 Short 2M CBSE
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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#13 Class 12 Physics Alternating Current 2021 Short 2M CBSE
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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#14 Class 12 Physics Alternating Current 2020 Short 2M CBSE
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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#15 Class 12 Physics Alternating Current 2022 Short 2M CBSE
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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#16 Class 12 Physics Alternating Current 2021 Short 2M CBSE
In a given circuit, the readings of voltmeters $V_1$ and $V_2$ are 300 V each. What are the readings of voltmeter $V_3$ and ammeter $A$? ($R = 100\ \Omega$, $X_L = X_C = 300\ \Omega$, series LCR circuit with 300 V sou...
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#17 Class 12 Physics Alternating Current 2022 Short 3M CBSE
An AC source of 200 V, 50 Hz is connected in series with a 300 $\Omega$ resistor and a capacitor of $\frac{25}{\pi}\ \mu$F. Calculate: (a) the reactance, (b) impedance, and (c) current in the circuit.
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#18 Class 12 Physics Alternating Current 2021 Short 2M CBSE
A coil has resistance 30 $\Omega$ and inductive reactance 20 $\Omega$ at 50 Hz. If an AC source of 200 V at 100 Hz is connected across the coil, find the current in the coil.
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#19 Class 12 Physics Alternating Current 2019 Short 1M CBSE
An AC voltage is applied to a resistance $R$ and an inductor $L$ in series. If $R$ and the inductive reactance are both equal to 3 $\Omega$, the phase difference between the applied voltage and the current in the circ...
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#20 Class 12 Physics Alternating Current 2020 Short 2M CBSE
A coil of inductance $\frac{4}{\pi}$ H is connected in series with a resistance of 30 $\Omega$. Calculate the current flowing when connected to AC mains of 200 V and 50 Hz.
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