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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.
| 251. |
the resistance and inductance of series circuit are `5Omega` and `20H` respectively. At the instant of closing the switch, the current is increasing at the rate `4A-s`. The supply voltage isA. 20 VB. 80 VC. 120 VD. 100 V |
| Answer» Correct Answer - B | |
| 252. |
A conducting ring is placed around the core of an electromagnet as shown in fig. qhen key `K` is pressed, the ring A. Remain stationaryB. Is attracted towards the electromagnetC. Jumps out of the coreD. None of the above |
| Answer» Correct Answer - C | |
| 253. |
In an `LR` circuit connected to a battery, the rate at which energy is stored in the inductor is plotted against time during the growth of current in the circuit. Which of the following best represents the resulting curve?A. B. C. D. |
| Answer» Correct Answer - A | |
| 254. |
A metalic ring is attached with the wall of a room. When the north pole of a magnet is brought near to it, the induced current in the ring will be A. ClockwiseB. AnticlockwiseC. Towards northD. Towards south 43 |
| Answer» Correct Answer - B | |
| 255. |
The figure shows certain wire segments joined together to form a coplaner loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time `I_(1) and I_(2)` are the currents in the segments ab and cd. Then, A. `I_(1) gt I_(2)`B. `I_(1) lt I_(2)`C. `I_(1)` is in the direction `ba` and `I_(2)` is in the direction `cd`D. `I_(1)` is in the direction `ab` and `I_(2)` is in the direction `dc` |
| Answer» Correct Answer - D | |
| 256. |
The dimensions of magnetic flux areA. `MLT^(-2) A^(-2)`B. `ML^(2)T^(-2)A^(-2)`C. `ML^(2)T^(-1)A^(-2)`D. `ML^(2)T^(-2)A^(-1)` |
| Answer» Correct Answer - D | |
| 257. |
A rectangular coil of `200` turns and area `100 cm^(2)` is kept perpendicular to a uniform magnetic field of induction `0.25` tesla. If the field is reversed in direction in `0.01` second, the average induced emf in the coil isA. `10^(6)V`B. `10^(4)V`C. `10^(2)V`D. zero |
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Answer» Correct Answer - C `e = (-NA(B_(2)-B_(1)))/("time") = (-NA(-B-B))/("time") = (2NAB)/("time")` |
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| 258. |
An aeroplane in which the distance between the tips of wings is `50 m` is flying horizontal with a speed of `360km//hr` over a place where the verticle components of earth magnetic field is `2.0xx10^(-4)webr//m^(2)`. The potential different between the tips of wings would beA. 0.1 VB. 1.0 VC. 0.2 VD. 0.01 V |
| Answer» Correct Answer - B | |
| 259. |
Conducting square loop of side `L` and resistance `R` moves in its plane with a uniform velocity `v` perpendicular to one of its sides. A magnetic induction `B`, constant in time and space, pointing perpendicular and into the plane of the loop exists everywhere. The current induced in the loop is A. `(Blv)/(R)` clockwiseB. `(Blv)/(R)` anticlockwiseC. `(2Blv)/(R)` anticlockwiseD. Zero |
| Answer» Correct Answer - D | |
| 260. |
The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it isA. `10^(4)V`B. `1.2 V`C. `1.0 V`D. `10^(-2)V` |
| Answer» Correct Answer - C | |
| 261. |
A copper disc of radius `0.1 m` rotates about its centre with `10` revolutuion per second in a uniform magnetic field of `0.1` tesla. The emf induced across the radius of the disc isA. `pi/10 V`B. `(2pi)/(10) V`C. `10 pi mV`D. `20 pi mV` |
| Answer» Correct Answer - C | |
| 262. |
A copper disc of radius `0.1 m` rotates about its centre with `10` revolutuion per second in a uniform magnetic field of `0.1` tesla. The emf induced across the radius of the disc isA. `(pi)/(10)V`B. `(2pi)/(10)V`C. `pi xx 10^(-2) V`D. `2pi xx 10^(-2) V` |
| Answer» Correct Answer - C | |
| 263. |
A coil having `500` square loops each of side `10 cm` is placed normal to a magnetic flux which increase at the rate of `1.0 "tesla"/"second"`. The induced r.m.f. in volts isA. `0.1`B. `0.5`C. 1D. 5 |
| Answer» Correct Answer - D | |
| 264. |
An e.m.f. of `100` millivolts is induced in a coil when the current in another nearby coil becomes `10` ampere from zero in `0.1` second. The coefficient of mutual induction between the two coils will beA. 1 millihenryB. 10 millihenryC. 100 millihenryD. 1000 millihenry |
| Answer» Correct Answer - A | |
| 265. |
A power transformer is used to step up an alternating e.m.f. of `220 V` to `11kv` to trannsmit `4.4 kW` of power. If the primary coil has `1000` turns, what is the current rating of the secondary?(Assume `100%` efficiency for the transformer)A. 4AB. 0.4 AC. 0.04AD. 0.2 A |
| Answer» Correct Answer - B | |
| 266. |
The working of dynamo is based on principle ofA. Electromagnetic inductionB. Conversion of energy into electricityC. Magnetic effects of currentD. Heating effects of current |
| Answer» Correct Answer - A | |
| 267. |
An alternating current of frequency 200 rad/sec and peak value 1 A as shown in the figure, is applied to the primary of a transformer. If the coefficient of mutual induction between theprimary and the secondary is 1.5 H , the voltage induced in the secondary will be A. `300 V`B. `191V`C. `200 V`D. `471V` |
| Answer» Correct Answer - B | |
| 268. |
A rectangular coil ABCD is rotated anticlockwise with a uniform angular velocity about the axis shown In the fig. the axis of rotation of the coil as well as the magnetic field `B` are horizontally.the induced emf in the coilwould be minimum when the plane of the coil A. The plane of the coil is horizontalB. The plane of the coil makes an angle of 45° with the magnetic fieldC. The plane of the coil is at right angles to the magnetic fieldD. The plane of the coil makes an angle of 30° with the magnetic field |
| Answer» Correct Answer - A | |
| 269. |
A rod of length `10 cm` made up of conducting and non-conducting material (shaded part is non-conducting). The rod is rotated with constant angular velocity `10 rad//s` about point `O`, in constant magnetic field of `2 T` as shown in the figure. The induced `emf` between the point `A` and `B` of rod will be: A. `0.029 V`B. `0.1 V`C. `0.051`D. `0.064 V` |
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Answer» Correct Answer - C `e = B omega int_(7)^(10)x dx = 0.051 V` |
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| 270. |
The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correctA. Lines of force minimum but induced e.m.f. is zeroB. Lines of force maximum but induced e.m.f. is zeroC. Lines of force maximum but induced e.m.f. is not zeroD. Lines of force maximum but induced e.m.f. is also maximum |
| Answer» Correct Answer - B | |
| 271. |
The phase difference between the flux linkage and the induced e.m.f. in a rotating coil in a uniform magnetic fieldA. `pi`B. `pi//2`C. `pi//4`D. `pi//6` |
| Answer» Correct Answer - B | |
| 272. |
A copper disc of radius `1m` is rotated about its natural axis with an angular velocity `2 "rad"//"sec"` in a uniform magnetic field `5` telsa with its plane perpendicular to the field. Find the emf induced between the centre of the disc and its rim. |
| Answer» `e = (1)/(2) B omega r^(2)`, `e = (1)/(2) xx 5 xx 2 xx 1 xx 1 = 5 "volt"` | |
| 273. |
A cycle wheel with `64` spokes is rotating with `N` rotations per second at right angles to horizontal component of magnetic field. The induced `e.m.f` generated between its axle and rim is `E`. If the number of spokes is reduced to `32` then the value of induced e.m.f. will beA. `E`B. `2E`C. `E//2`D. `E//4` |
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Answer» Correct Answer - A `E.M.F.` is independent of no of spokes here. |
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| 274. |
A metal rod of length `1m` is rotated about one of its ends in a plane at right angles to a uniform magnetic field pf induction `2.5 xx 10^(-3) Wb m^(-2)`. If it makes `1800` rpm, then the induced emf between its ends approximately isA. `0.24 V`B. `0.12 V`C. `0.36 V`D. `0.48 V` |
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Answer» Correct Answer - A `epsilon = (1)/(2)B omega l^(2)` |
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| 275. |
Find the linear speed the bicycle required to power its head light by a generator, whose rubber shaft presses against the wheel of cycle of radius `0.33 m`, turns at an angular speed of `44` times as great as the angular speed of the tire itself. The coil consists of `75` turns, has an area of `2.6 xx 10^(-3) m^(2)`, and rotates in a `0.10 T` magnetic field. When the peak emf being generated is `6.0 V`.A. `2.5 m//s`B. `5 m//s`C. `2.3 m//s`D. `4.6 m//s` |
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Answer» Correct Answer - C `v = r((1)/(44)) omega_("coil")` where `omega_("coil") = (e.m.f)/(NAB)` |
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| 276. |
A thin semicircular conducting ring of radius `R` is falling with its plane verticle in a horizontal magnetic inducting `B`. At the position `MNQ`, the speed of the ring is `V` and the potential difference developed across the ring is A. ZeroB. `Bvpi R^(2)//2` and M is at higher potentialC. `pi R B V` and Q is at higher potentialD. 2 RBV and Q is at higher potential |
| Answer» Correct Answer - D | |
| 277. |
A thin semicircular conducting ring of radius `R` is falling with its plane verticle in a horizontal magnetic inducting `B`. At the position `MNQ`, the speed of the ring is `V` and the potential difference developed across the ring is A. zeroB. `BV pi R^(2)//V` and `M` is at higher potentialC. `pi RBV` and `Q` is at higher potentialD. `2RBV` and `Q` is at higher potential |
| Answer» Correct Answer - D | |