InterviewSolution
Saved Bookmarks
InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
One weber is the amount of ……………………over an area of ……………………….. Held normal to a uniform |
| Answer» Correct Answer - magnetic flux; `1 m^(2)` ; magneitc field of `1 Wb//m^(2)` | |
| 52. |
Mutual inductance of two coils can be increased byA. decreasing the number of turns on the coilsB. increasing the number of turns on the coilsC. winding the coils on the wooden coreD. none of these |
| Answer» Correct Answer - B | |
| 53. |
If the current through a solenoid changes with time electromagnetic induction takes place in the solenoid. This is known as self-induction. In general, for a current I, the induced emf in the coil is `e=-L(dI)/(dt)`. L is the self-inductance of the solenoid. On the other hand, such change in the current in a solenoid can produce electromagnetic induction in another adjacent solenoid. The induced emf in the other solenoid `e=-M(dI)/(dt)`, M is called the mutual inductance of the solenoids. If `L_(1)` and `L_(2)` are the self-inductance of the adjacent coils then their mutual inductance `M=ksqrt(L_(1)L_(2))`. If the magnetic flux produced by the current in one coil is totally linked with the other coil then k = 1. Self-inductance (in H) of the coil in question (III) isA. 0.1B. 0.08C. 0.01D. 0.008 |
| Answer» Correct Answer - D | |
| 54. |
If L and R denote inductance and resistance respectively, then the dimension of `(L)/(R )` isA. `M^(0)L^(0)T^(0)`B. `M^(0)L^(0)T^(1)`C. `M^(2)L^(0)T^(2)`D. `M^(1)L^(1)T^(2)` |
| Answer» Correct Answer - B | |
| 55. |
Dimension of magnetic flux isA. `ML^(2)T^(-2)A^(-1)`B. `MLT^(-1)A^(-2)`C. `ML^(-1)TA^(-1)`D. `ML^(-1)A` |
| Answer» Correct Answer - A | |
| 56. |
What is the relation between the unit: weber and volt? |
| Answer» Correct Answer - `1Wb=1V.1s` | |
| 57. |
The induced emf between the two ends of a straight conductor moving perpendicular to its axis in a uniform magnetic field isA. proportional to the length of the conductorB. proportional to the velocity of the conductorC. proportional to the magnetic fieldD. inversely proportional to the magnetic field |
| Answer» Correct Answer - A::C::D | |
| 58. |
Show that the units of RC and `(L)/(R )` are of time. R, L and C carry their usual significances. |
|
Answer» Unit of `RC=OmegaxxF=(V)/(A)xx(C)/(V)=(C)/(A)=(C)/((C)/(s))=s` So, the unit of RC and the unit of time are the same. Again, according to the law of electromagnetic induction, `e=-L(dI)/(dt)` So, `V=Hxx(A)/(s)or,(V)/(A)xxs=H` or, `Omegaxxs=H or,(H)/(Omega)=s` So, the unit of `(L)/(R )` and the unit of time are the same. |
|
| 59. |
Self-inductance of a coil is 1H. If 1A current passes through it, what will be the magnetic flux linked with the coil? |
| Answer» Correct Answer - `1Wb` | |
| 60. |
What is the relation between the units: tesla and weber? |
| Answer» Correct Answer - `1T=(1Wb)/(1m^(2))` | |
| 61. |
A long straight current carrying wire passes normally through the centre of circular loop. If the current through the wire increases, will there be an induced emf in the loop? Justify. |
|
Answer» We know that, induced emf, `e=-(dphi)/(dt)=-(d)/(dt)(vecB.vecA)` In this case, the magnetic lines of force due to current carrying wire are parallel to the plane of the loop. So, angle between the magnetic field and normal of the plane of the circular loop is `90^(@)`. `therefore e=0[because vecB.vecA=0]` Hence, there will no induced emf in the loop. |
|
| 62. |
In the relation `phi = BA cos theta, theta` is angleA. which normal to surface area makes with the direction of magnetic fieldB. which magnetic field makes with the surfaceC. which is never constantD. none of the above |
| Answer» Correct Answer - A | |
| 63. |
The relation `(E_(s))/(E_(P)) = (n_(s))/(n_(P))` is applicable only beA. a.c. generatorB. d.c. generatorC. induction coilD. stepup/down transformer |
| Answer» Correct Answer - D | |
| 64. |
What is the relation between the units of self-inductance and mutual inductance? |
| Answer» they have the same unit | |
| 65. |
What is the relation between the units: weber and ampere? |
| Answer» Correct Answer - `1Wb=1A.1H` | |
| 66. |
A 10m long horizontal wire, lying along the magnetic east-west direction, begins to fall with a velocity of 5.0 m. `s^(-1)`. What will be the emf induced in the wire? [Given, `H=0.3xx10^(-4)Wb.m^(-2)`] |
| Answer» Correct Answer - `1.5xx10^(-3)V` | |
| 67. |
In which of the following devices, the eddy current effect is not used ?A. Magnetic breaksB. speedometersC. Induction furnaceD. Transformers |
| Answer» Correct Answer - D | |
| 68. |
A circular coil expands radially in a region of magnetic field but no electromotive force is produced in the coil. It can be becauseA. the magnetic field is constantB. the magnetic field is in the same plane as the circular coil and it may or may not varyC. the magnetic field may have a perpendicular (to the plane of the coil) component with suitably decreasing magnitudeD. there is a constant magnetic field perpendicular (to the plane of the coil) direction |
|
Answer» Correct Answer - B::C When magnetic field is in the plane of the coil, no magnetic flux is linked with the coil. Since there is no change in magnetic flux linked with coil, induced emf is zero. When magnetic field perpendicular to the plane of the coil decreases suitably and the magnetic flux linked with the coil remains constant, e = 0. |
|
| 69. |
Out of the following choose the correct relationA. 1 henry `= (1 "volt")/(1 "ampere")`B. 1 henry `= (1 "amp")/(1 "volt")`C. 1 henry `= (1 "volt")/(1 amp//sec)`D. 1 henry `= (1 "volt")/(1 amp.sec)` |
| Answer» Correct Answer - C | |
| 70. |
Now assume that the straight wire carries a current of 50 A and the loop is moved to the right with a constant velocity `v=10m.s^(-1)`. Calculate the induced emf in the loop at the instant when x = 0.2 m. Take a = 0.1 m and assume that the loop has a large resistance. |
|
Answer» Induced emf, `e=(mu_(0))/(2pix).(Ia^(2)v)/(a+x)=(2xx10^(-7)xx50xx(0.1)^(2)xx10)/(0.2(0.1+0.2))` `=1.67xx10^(-5)~~1.7xx10^(-5)V` |
|
| 71. |
An emf is produced in a coil, which is not connected to an external voltage source. This can be due toA. the coil being in a time-varying magnetic fieldB. the coil moving in a time-varying magnetic fieldC. the coil moving in a constant magnetic fieldD. the coil is stationary in external spatially varying magnetic field, which does not change with time |
|
Answer» Correct Answer - A::B::C When a coil is not connected to an external source of voltage, then emf in the coil is produced due to changing magnetic flux with time, `e=-(dphi)/(dt)` |
|
| 72. |
Self inductance of a solenoid varies……………………as the ………………of the number of turns in the solenoid. |
| Answer» Correct Answer - directly ; square. | |
| 73. |
The number of turns of a solenoid of length l and area of cross-section A is N. The self-inductance L increases asA. l and A increaseB. l decreases and A increasesC. l increases and A decreasesD. both l and A decrease |
|
Answer» Correct Answer - B `L=(mu_(0)N^(2)A)/(l)` |
|
| 74. |
When number of turns of a solenoid is doulbed, its self inductance becomes k time, where k =A. 2B. 1C. 8D. 4 |
| Answer» Correct Answer - D | |
| 75. |
Two differenct coils have self-inductances `L_(1)=16 mH` and `L_(2)=12mH`. At a certain instant, the current in the two coils is increasing at the same rate and power supplied to the two coils is the same. Find the ratio of induced voltage |
| Answer» Correct Answer - `4:3` | |
| 76. |
Self-inductance of a coil is 2mH, current through this coil is, `I=t^(2)e^(-t)` (t = time). After how much time will the induced emf be zero? |
|
Answer» Induced emf, `E=-L(dI)/(dt)` Now, `(dI)/(dt)=(d)/(dt)(t^(2)e^-t)=2te^(-t)-t^(2)e^(-t)` `=-e^(-t).t(t-2)` Hence, `E=Le^(-t)t(t-2)` So, if E = 0, then t = 0 or 2 Therefore, after 2s from the initial moment, the induced emf will be zero. |
|
| 77. |
The self-inductance of a long straight solenoid is L. Each of the length, the diameter and the number of turns of another solenoid is double that of the first. The self-inductance of the second solenoid isA. 2LB. 4LC. 8LD. 16L |
| Answer» Correct Answer - C | |
| 78. |
The self inductances of two coils are 16 mH and 25 mH, and they have a mutual inductances of 10 mH. Their coupling constant isA. 0.025B. 0.05C. 0.25D. 0.5 |
| Answer» Correct Answer - D | |
| 79. |
A current flowing through a coil changes from +2A to -2A in 0.05 s and an emf of 8 V is induced in the coil. The value of self-inductance of the coil isA. 0.8 HB. 0.1 HC. 0.2 HD. 0.4 H |
|
Answer» Correct Answer - B We know, `e=-L(dI)/(dt)` or, `L=(-edt)/(dI)=(8xx0.05)/(-2-(+2))=(0.4)/(4)=0.1H` |
|
| 80. |
The self-inductance of a circular coil of 600 turns is 36 mH. What will be the self-inductance of another circular coil of identical shape, but of 500 turns? |
| Answer» Correct Answer - 25 mH | |
| 81. |
Self-inductance and resistance of a coil are 30mH and `20Omega` respectively. It is connected to a `30Omega` resistance and a 2V battery in series. How much energy will be stored in the coil? |
| Answer» Correct Answer - `2.4xx10^(-5)J` | |
| 82. |
A closed circular coil having a diameter of 50 cm and of 200 turns, with a total resistance of `10Omega` is placed with its plane at right angles to a magnetic field of strength `10^(-2)T`. Calculate the quantity of electric charge that flows through it when the coil is turned through `180^(@)` about its diameter. |
| Answer» Correct Answer - `0.078C` | |
| 83. |
Resistance of a coil is `10Omega` and its self inductance is 5H. Find the energy stored when it is connected with a 100V battery. |
|
Answer» Current in circuit, `I=(V)/(R)=(100)/(10)=10A` Stored energy in the inductor `=(1)/(2)LI^(2)=(1)/(2)xx5xx(10)^(2)=250J` |
|