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question_answer1)
A square of side L meters lies in the x-y plane in a region where the magnetic field is given by \[\operatorname{B}={{B}_{0}}\text{ (}2\hat{i}+3\hat{j}+4\hat{k})\] Testa, where \[{{B}_{0}}\] is constant. The magnitude of flux passing through the square is
A)
\[2{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\] done
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B)
\[3{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\] done
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C)
\[4{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\] done
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D)
\[\sqrt{29}{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\] done
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question_answer2)
A loop, made of straight edges has six corners at A (0, 0, 0), B (L, 0, 0) C (L, L, 0), D (0, L,0), E (0, L, L) and F (0,0, L). A magnetic field B= \[{{B}_{0}}\text{ }(\hat{i}+\hat{k})\] Testa is present in the region. The flux passing through the loop ABCDEFA (in that order) is
A)
\[{{B}_{0}}{{L}^{2}}Wb\]. done
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B)
2\[{{B}_{0}}{{L}^{2}}Wb\]. done
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C)
\[\sqrt{2}{{B}_{0}}{{L}^{2}}Wb\]. done
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D)
\[4{{B}_{0}}{{L}^{2}}Wb\] . done
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question_answer3)
A cylindrical bar magnet is rotated about its axis in the figure. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then |
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A)
a direct current flows in the ammeter A. done
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B)
no current flows through the ammeter A. done
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C)
an alternating sinusoidal current flows through the ammeter A with a time period \[2\pi /\omega \] done
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D)
a time varying non-sinusoidal current flows through the ammeter A. done
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question_answer4)
There are two coils A and B as shown in figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counter clockwise. B is kept stationary when A moves. We can infer that |
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A)
there is a constant current in the clockwise direction in A. done
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B)
there is a varying current in A. done
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C)
there is no current in A. done
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D)
there is a constant current in the counter clockwise direction in A. done
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question_answer5)
Same as problem 4 except the coil A is made to rotate about a vertical axis figure. No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counter-clockwise and the coil A is as shown at this instant, t = 0, is |
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A)
constant current clockwise. done
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B)
varying current clockwise. done
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C)
varying current counter-clockwise. done
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D)
constant current counter-clockwise. done
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question_answer6)
The polarity of induced emf is defined by
A)
Ampere's circuital law. done
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B)
Biot-Savart law. done
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C)
Lenz's law. done
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D)
Fleming's right hand rule. done
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question_answer7)
Lenz's law is consequence of the law of conservation of
A)
Charge done
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B)
mass done
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C)
energy done
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D)
momentum done
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question_answer8)
The magnetic flux linked with a coil is given by an equation \[\phi =5{{t}^{2}}+2t+3\]. The induced e.m.f. in the coil at the third second will be
A)
32 units done
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B)
54 units done
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C)
40 units done
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D)
65 units done
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question_answer9)
The self-inductance L of a solenoid of length I and area of cross-section A, with a fixed number of turns N increases as
A)
I and A increase. done
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B)
I decreases and A increases. done
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C)
I increases and A decreases. done
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D)
both I and A decrease. done
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question_answer10)
An iron-cored solenoid has self-inductance 2.8H. When the core is removed, the self-inductance becomes 2 mH. The relative permeability of the material of the core is
A)
1400 done
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B)
1200 done
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C)
2800 done
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D)
2000 done
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question_answer11)
In which of the following application, eddy current has no role to play?
A)
Electric power meters done
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B)
Induction furnace done
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C)
LED lights done
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D)
Magnetic brakes in trains done
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question_answer12)
Which one of the following statements is wrong?
A)
Eddy currents are produced in a steady magnetic field. done
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B)
Eddy current is used to produce braking force done
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C)
Eddy currents is minimized by using l aminated core. done
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D)
Induction furnace uses eddy current to produce heat done
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question_answer13)
If the back e.m.f. induced in a coil, when current changes from 1A to zero in one millisecond, is 5 volts, the self-inductance of the coil is
A)
5 H done
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B)
1 H done
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C)
5\[\times {{10}^{-3}}\operatorname{H}\] done
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D)
5\[\times {{10}^{3}}\operatorname{H}\] done
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question_answer14)
Magnetic field energy stored in a coil is
A)
\[{{\operatorname{Li}}^{2}}\] done
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B)
\[\frac{1}{2}\operatorname{Li}\] done
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C)
\[\operatorname{Li}\] done
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D)
\[\frac{1}{2}{{\operatorname{Li}}^{2}}\] done
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question_answer15)
If two coils of self inductance \[{{\operatorname{L}}_{1}}\] and \[{{\operatorname{L}}_{2}}\] are coupled together, their mutual inductance becomes
A)
\[\operatorname{M}=k\sqrt{{{\operatorname{L}}_{1}}{{L}_{2}}}\] done
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B)
\[\operatorname{M}=k\sqrt{\frac{{{L}_{1}}}{{{L}_{2}}}}\] done
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C)
\[\operatorname{M}=k\sqrt{{{\operatorname{L}}_{1}}+{{L}_{2}}}\] done
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D)
None of the above done
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question_answer16)
An inductor and a bulb are connected in series with a dc source. A soft iron core is then inserted in the inductor. What will happen to intensity of the bulb?
A)
Intensity of the bulb remains the same. done
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B)
Intensity of the bulb decreases. done
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C)
Intensity of the bulb increases done
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D)
The bulb ceases to glow. done
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