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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.
| 351. |
An iron bar of length `10 cm` and diameter `2 cm` is placed in a magnetic field of intensity `1000Am^(-1)` With its length parallel to the direction of the field. Determine the magnetic moment produced in the bar if permeability of its material is `6.3xx10^(-4) TmA(-1)`. |
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Answer» we know that, `mu=mu_(0)(1+chi)` `rArr chi=(mu)/(mu_(0))-1=(6.3xx10^(-4))/(4pixx10^(-7))-1=500.6` Intensity of magnetisation, `I=chiH=500.6xx1000=5xx10^(5) Am^(-1)` `there` magnetic moment, `M=IxxV=Ixxpir^(2)l` `=5xx10^(5)xx3.14xx(10^(-2))^(2)xx(10xx10^(-2))=17.70A-m^(2)` |
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| 352. |
The work done in rotating a magnet of pole strength `1 A-m` and length `1 cm` through an angle of `60^(@)` from the magnetic meridian is `(H=30A//m)`A. `9.42xx10^(-8)J`B. `3.14xx10^(-8)J`C. `18.84xx10^(-8)J`D. `10xx10^(-8)J` |
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Answer» Correct Answer - C `W=mxx2l B[cos theta_(1)-cos theta_(2)]` |
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| 353. |
The magnetic moment of a magnet of mass `75 gm` is `9xx10^(-7) A-m^(2)`. If the density of the material of magnet is `7.5xx10^(3) kg m^(-3)`, then find intensity of magnetisation isA. `0.9A//m`B. `0.09A//m`C. `9A//m`D. `90A//m` |
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Answer» Correct Answer - B `I=(M)/(V)` |
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| 354. |
The correct value of dip angle at a place is `45^(@)`. If the dip circle is rotated by `45^(@)` out of the meridian, then the tangent of the angle of apparent dip at the place isA. `1`B. `1//2`C. `1sqrt2`D. `sqrt2` |
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Answer» Correct Answer - D `tan delta=(B_(V))/(B_(H))` and `tan delta^(1)=(B_(V)^(1))/(B_(H)^(1))=(B_(V))/(B_(H) cos 45^(@))` `tan delta^(1)=(tan delat)/(cos 45)` |
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| 355. |
The magnetic moment of a bar magnet is 2A m2. if the magnetic length of the bar magnet is 5 cm, determine the force acting on it an external magnetic field of strength 0.6 T. |
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Answer» Magnetic moment, `M=2Am^(2)` Magnetic length , `2l=5 cm =5xx10^(-2) m`. Magnetic field, B=0.6 T `B=("force")/("pole strength(m)")` `F=Bxxm, M=mxx2l` `2=mxx5xx10^(-2)` `m=(2xx100)/5=40 Am` `:. F=0.6 xx40 =24 N` |
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| 356. |
A coil is made of an insulated copper wire and current is passed through the coil. Now, two magnets are kept at each end of the coil with the polarity as shown in the figure below. If the magnets do not move, will there be any change in the length of the coil ? what will happen on reversing the direction of current ? |
| Answer» Direction of M.F. due to a current carrying conductor. Relation between thickness of the wire and strength of the current Relation between strength of the current and strength of the magnetic field | |
| 357. |
Determine the magnetic moment of a bar magnet of magnetic length 5 cm and pole strength 2A m. |
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Answer» Magnetic moment=pole strength x magnetic length `=2xx Am (5xx10^(-2))m=1xx10^(-1) Am^(2)` |
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| 358. |
Can the combination of a current carrying wire and a solenoid produce neutral points ? |
| Answer» The null points are obtained due to the cancellation of two magnetic field equal in magnitude and opposite in direction. Current carrying conductor can produce a magnetic field around it. | |
| 359. |
In the shown in the figure `AC` and `BD` are straight lines and `CED` and `AFB` are semicircular with radii `r` and `4r`, respectively. The centre setip is lying in the same plane. If `i` is current entering at `A` what fraction of `i` will flow in the `ACEDB` such that resultant magnetic field at `O` is zero. A. `I//5`B. `4I//5`C. `3I//5`D. no current through bigger semicircular part. |
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Answer» If `I_(1)` is current in `ACDB` then `(mu_(0))/(4)*(i_(1))/(r )=(mu_(0))/(4)*(i_(2))/(4r)rArr(i_(1))/(i_(2))=(1)/(4)` `i_(1)=(1)/(5)xxi=(i)/(5)` |
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| 360. |
The space inside a toroid is filled with tungsten whose susceptibility is `6.8xx10^(-5)` . The percentage increase in the magnetic field will beA. `0.0068%`B. `0.068%`C. `0.68%`D. None of these |
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Answer» Correct Answer - A When space inside the toroid is filled with air ,`B_(0)=mu_(0)H`. When filled wiith tungsten , we get `B=muH=mu_(0)mu_(r)H=mu_(0)(1+ chi_(m))H` Percentage increase in magnetic field ` =((B-B_(0)) xx 100)/( B_(0))=(mu_(0) chi_(m)H xx 100)/( mu_(0)H)=chi_(m) xx 100 ` `=6.8xx10^(-5) xx 100=0.0068%` |
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| 361. |
Relative permeability of iron is 4000. What is its magnetic susceptibility ?A. 4001B. 3999C. `4000xx10^(-2)`D. `4000 xx 10^(2)` |
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Answer» Correct Answer - B We know that `chi_(m)=mu_(r)=-1 implies chi_(m)=4000-1=3999` |
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| 362. |
A solenoid of 600 turns per metre is carrying a current of 4 A . Its core is made of iron with relative permeability of 5000. Calculate the intensity of magnetisation and magnetic field inside the core .A. `1.2xx10^(7) Am^(-1) and 15T`B. `2.3 xx 10^(9) Am^(-1) and 13T `C. `2.7 xx 10^(11) Am^(-1) and 16T `D. `1.8 xx 10^(6) Am^(-1) and 14 T ` |
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Answer» Correct Answer - A Give , `i=4A, mu_r=5000 , n=600 tunrs , I=? and B=?` Now , calculate the value of magnetic intensity H using the formula , `H=ni =600m^(-1) xx 4A=2400 Am^(-1)` Using the relation , `mu_(r)=1+ chi_(m)`, calculate the value of magnetic susceptibility . `chi_(m)=mu_(r)-1=5000-1 ` `=4999~~5000` Now , using the value of ` chi_(m)` to calculate the intensity of magnetisation `I=chi_(m)H=5000 xx 2400 Am^(-1)` `=1.2xx10^(7)Am^(-1)` Now calculate the value of magnetic field B inside the core , using the formula , `B=muH=mu_(4)mu_(0)H` `B=mu_(r) mu_(0)H=5000 mu_(0)H=5000 xx(4pi xx 10^(-7)) xx 2400T ` `:. B=15T ` |
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| 363. |
A bar magnet of magnetic moment `3.0 A-m^(2)` is placed in a uniform magnetic induction field of `2xx10^(-5)T`. If each pole of the magnet experiences a force of `6xx10^(-4)N`, the length of the magnet isA. `0.5 m`B. `0.3 m`C. `0.2 m`D. `0.1 m` |
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Answer» Correct Answer - D `F=mB` `M=mxx2l` |
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| 364. |
In case of a bar magnet, lines of magnetic inductionA. start form the south pole and end at the north pole .B. run continously through the bar magnet and outside.C. emerge in circular paths from the middle of the barD. are produced only at the north pole like rays of light form a bulb |
| Answer» Correct Answer - B | |
| 365. |
When a bar magnet of magnetic moment `barM` is placed in a magnetic field of induction field strength `barB`, each pole experiences a force of `barF` then the distance between the south and north pole of the magnet measured inside it isA. `MBF`B. `(MB)/(F)`C. `(F)/(MB)`D. `(FB)/(M)` |
| Answer» Correct Answer - B | |
| 366. |
When two identical bar magnets placed one above the other, such that they are mutually perpendicular and bisect each other. The time period oscillation in a horizontal magnetic field is `4` seconds. If one of the magnets is removed the time period of the other in the same field `(2^(1//4)=1.189)`A. `1.34sec`B. `2.34sec`C. `3.36sec`D. `4.34sec` |
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Answer» Correct Answer - C `T=2pisqrt((I)/(MB_(H))` and `(T_(1))/(T_(2))=sqrt((I_(1))/(I_(2))xx(M_(2))/(M_(1)))=sqrt((2I)/(I)xx(M)/(sqrt2M))=2^(1//4)` |
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| 367. |
Two identical bar magnets are placed on above the other such that they are mutually perpendicular and bisect each other. The time period of this combination in a horizontal magnetic field is T. The time period of esch magnet in the same field isA. `sqrt(2)T`B. `2^((1)/(4))T`C. `2^(-(1)/(4))T`D. `2^(-(1)/(2))T` |
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Answer» Correct Answer - C |
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| 368. |
Two bar magnets are placed on a piece of cork which folats on water. The magnets are so placed that their axis are mutually perpendicular. Then the corkA. rotatesB. move a sideC. oscillatesD. neither rotates nor oscillates |
| Answer» Correct Answer - D | |
| 369. |
The incorrect statement regarding the lines of force of the magnetic field `B` isA. Magnetic intensity is a measure of lines of force passing through unit area held normal to itB. Magnetic lines of force form a closed curveC. Inside a magnet, its magnetic lines of force move form north pole of a magnet towards its south poleD. Magnetic lines of force never cut each other |
| Answer» Correct Answer - C | |
| 370. |
The electric and magnetic field lines differ in thatA. electric line of force are closed curves while magnetic filed lines are notB. magnetic field lines are closed while electric lines are notC. electric field of force can give direction of the electric field while magnetic lines can notD. magnetic field while electirc lines can not. |
| Answer» Correct Answer - B | |
| 371. |
The source of magnetic field isA. isolated magnetic poleB. static electric chargeC. current loopD. moving light source |
| Answer» Correct Answer - C | |
| 372. |
There is no. couple acting when two bar magnets are placed co-axially separated by a distance becauseA. There are no forces on the polesB. The forces are parallel and their lines of action do not coincide (C. The forces are perpendicular to each otherD. The forces act along the same line |
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Answer» Correct Answer - D |
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| 373. |
A small hole is made at the centre of the magnet then its magnetic momentA. decreasesB. increasesC. remains sameD. depends on the nature of the magnetic materical |
| Answer» Correct Answer - A | |
| 374. |
Magnetic moment of a bar magnet is 2.4 `Am^(2)`A point is situated at 20 cn from its centre on a line making an angle of `30^(@)`with axis.The magnetic induction at that point isA. `5.42xx10^(-5) Wb//m^(2)`B. `5.14xx10^(-5) Wb//m^(2)`C. `4.51xx10^(-5)Wb//m^(2)`D. `4.15xx10^(-5)Wb//m^(2)` |
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Answer» Correct Answer - A `B=mu_(0)/(4pi)(M)/(r^(3))sqrt(3cos^(2)theta+1)` `(4pixx10^(-7)xx2.4)/(4pixx(0.2)^(3))sqrt(3cos^(2)30+1)` `~~5.41xx10^(-5)Wb//m^(2)` |
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| 375. |
If a hole is made at the centre of a bar magnet, then its magnetic moment willA. IncreaseB. DecreaseC. Not changeD. None of these |
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Answer» Correct Answer - C |
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| 376. |
The sensitivity of a tangent galvanometer is increased ifA. Number of turn decreasesB. Number of turn increasesC. Field increasesD. None of the above |
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Answer» Correct Answer - B |
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| 377. |
Give reasons for the following.Magnets are used to close the doors of a refrigerator tightly. |
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Answer» Because of the attractive property of a magnet. A magnet attracts magnetic substances by exerting a force called magnetic force. , This keeps the door of a refrigerator closed tightly. |
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| 378. |
Give reasons for the following.Electromagnets are temporary magnets. |
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Answer» An electromagnet is a temporary magnet because it behaves like a magnet only till the current is passed through it. When the ~ current is stopped, it stops behaving like a magnet. |
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| 379. |
In which of the following devices temporary magnets are used ?A. DynamoB. Electric motorsC. GeneratorsD. Electric cranes |
| Answer» Correct Answer - D | |
| 380. |
Magnetic lines of force areA. directed from the north pole to south pole in the magnetic field.B. directed from the south pole to north pole inside a magnet.C. closed loopsD. All the above |
| Answer» Correct Answer - D | |
| 381. |
Match the entries in column A with the appropriate ones in Column B |
| Answer» Correct Answer - A: g B: I C:f D:a E:h F:j G:e H:b I:c J:d | |
| 382. |
A solenoid is ____________A. an electromagnetB. a temporary magnetC. a permanent magnetD. Both a and (b) |
| Answer» Correct Answer - D | |
| 383. |
Consider the statement A and B given below and select the correct choice (A) : an EM relay operates on high voltage (b) : An EM relay cantrols high voltage circuit.A. Only A is trueB. Only A is falseC. Both are trueD. Both are false |
| Answer» Correct Answer - B | |
| 384. |
The force experienced by a particle having mass m and charge q accelerated through a potential difference V when it is kept under perpendicular magnetic field \(\vec B\) is |
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Answer» Correct answer is (c)\(\sqrt{\frac{2q^3B^2V}{m}}\) |
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| 385. |
An electron moves straight inside a charged parallel plate capacitor of uniform charge density σ The time taken by the electron to cross the parallel plate capacitor when the plates of the capacitor are kept under constant magnetic field of induction \(\vec B\) is- |
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Answer» Correct answer is (d) ε0\(\frac{lB}{σ }\) |
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| 386. |
The end of a freely suspened magnet which points to the magnetic north of earth is _______ |
| Answer» Correct Answer - South pole | |
| 387. |
A permanent magnet can be demagnetized by1. hammering2. heating3. rough handling4. all of these. |
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Answer» 4. all of these. |
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| 388. |
The region around a magnet where its magnetic force can be experienced is called1. magnetic axis2. magnetic equator3. magnetic field4. magnetic poles |
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Answer» 3. magnetic field |
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| 389. |
Vibration magnetometer works on the principle ofA. Torque acting on the bar magnetB. Force acting on the bar magnetC. Both the force and the torque acting on the bar magnetD. None of these |
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Answer» Correct Answer - A |
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| 390. |
A bar has a magnetic moment equal to `5xx10^(-5) weberxxm`. It is suspended in a magnetic field which has a magnetic induction (B) equal to `8pixx10^(-4)` tesla. The magnet vibrates with a period of vibration equal to 15 sec. The moment of intertia of the magnet isA. `22.5kgxxm^(2)`B. `11.25xxkgxxm^(2)`C. `5.62xxkgxxm^(2)`D. `7.16xx10^(-7)kg-m^(2)` |
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Answer» Correct Answer - D |
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| 391. |
A bar magnet has a length of 8cm. The magnetic field at a point at a distnace 3cm from the centre in the broadside-on position is found to be `4 xx 10^(-6) T`. Find the pole strength of the magnet. |
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Answer» Correct Answer - `6 xx 10^(-5)` Am |
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| 392. |
An electric bell works on the principle of ______A. magnetic inductionB. attractive property of magnetsC. electromagntismD. All the above |
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Answer» Correct Answer - D The working of an electric bell involves magnetic induction, attractive property of magnets and electromagnetism |
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| 393. |
The angle of declination is ________A. `90^(@)` at the polesB. `0^(@)` at the equatorC. variableD. none of the above |
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Answer» Correct Answer - C The angle of declination changes from place to place even along magnetic equator. |
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| 394. |
Which of the following substance is repelled by strong magnet ?A. IronB. PlatinumC. GoldD. Aluminium |
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Answer» Correct Answer - C Gold is a diamangnetic substance and it is repelled by magnets. |
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| 395. |
Which of the following substance is independent of temrature?A. DiamagnetivB. ParamagneticC. FerromagneticD. None of these |
| Answer» Correct Answer - A | |
| 396. |
The substances,Which are repelled by a magnet,are termed asA. DiamagneticB. ParamagneticC. FerromagneticD. Electromagnetic |
| Answer» Correct Answer - A | |
| 397. |
The universal proporty among all substance isA. DiamagnetismB. FerromagnetismC. ParamagnetismD. All of these |
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Answer» Correct Answer - A |
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| 398. |
The magnetic susceptibility is negative forA. Paramagnetic materialsB. Diamagnetic materialsC. Ferromagnetic materialsD. Paramagnetic and ferromagnetic materials |
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Answer» Correct Answer - B |
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| 399. |
Define the Curie temperature. |
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Answer» Curie temperature is the temperature above which a ferromagnetic substance becomes a paramagnetic substance. |
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| 400. |
The number of turns and radius of cross-section of the coil of a tangent galvanometer are doubled. The reduction factor K will beA. KB. 2KC. 4KD. `K//4` |
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Answer» Correct Answer - A |
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