InterviewSolution
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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.
| 1. |
When a current carrying coil is placed in a uniform magnetic field of induction `B`, then a torque `tau` acts on it. If `I` is the current, `n` is the number of turns and `A` is the face area of the coil and the normal to the coil makes an angle `theta` with `B`, ThenA. `tau= n I AB`B. `tau= n I AB cos theta`C. `tau = n I AB sin theta`D. `tau = n I AB tan theta` |
| Answer» Correct Answer - C | |
| 2. |
The magnetic induction at apoint P which is at the distance 4 cm from a long current carrying wire is `10^(-3) T`. The field of induction at a distance 12 cm from the current will beA. `3.33xx10^(-9)`teslaB. `1.11xx10^(-4)` teslaC. `3xx10^(-3)` teslaD. `9xx10^(-2)` tesla |
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Answer» Correct Answer - A The magnetic field `beta =(mu_(0))/(2pi)-(2i)/(r ) therefore (beta_(1))/(beta_(2))=(r_(2))/(r_(1))` `(10^(-8))/(beta_(2))=12/14 rarrbeta_(2)=3.33 xx10^(-4) T` |
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| 3. |
The field due to a long straight wire carrying a current I is proportional toA. IB. `sqrt(I)`C. `I^2`D. `1//I` |
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Answer» Correct Answer - A `B=(mu_0I)/(2pia)because BpropI` |
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| 4. |
In cyclotron for a given magnet radius of the semicircle traced by positive ion is directly proportional to (where v= velocity of positive ion)A. `v^-2`B. `v^-1`C. `v`D. `v^2` |
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Answer» Correct Answer - C `r=(mv)/(q B)` Since , `(v)/(q B)` is current `therefore r propv`. |
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| 5. |
The voltage sensitvity of M.C.G. is given byA. `S=(n AB)/(K)`B. `S=(n AB)/(KG)`C. `S= n ABKG`D. `S=(KG)/(n AB)` |
| Answer» Correct Answer - B | |
| 6. |
A straight wire of length 1 m, and carrying a current of 1.8 A, is placed in a uniform magnetic field of induction 2T. If the magntic field is perpendicular to the length of the wire, then the force acting on the wire isA. 1.8 NB. 3.6NC. 0.9ND. 2.5N |
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Answer» Correct Answer - B `F=Iblsintheta=1.8xx2xx1xxsin90=3.6N` |
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| 7. |
The maximum velocity to which a proton can be accelerated in a cyclotron of 10 MHZ frequency and radius 50 cm isA. `6.28xx10^(8) ms^(-1)`B. `3.14xx10^(8) ms^(-1)`C. `6.28xx10^(7) ms^(-1)`D. `3.14 xx10^(7) ms^(-1)` |
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Answer» Correct Answer - D The motion of proton in magnetic field will be circular `therefore v=2 pi rf=2xx3.14x50xx10^(-2)xx10xx10^(6)` `=3.14 xx10^(7)ms^(-1)` |
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| 8. |
If the radius of the dees of cyclotron is r then the kinetic energy of a proton of mass m accelerated by the cycloton at an oscillating frequency v isA. `4pi^(2)m^(2)v^(2)r^(2)`B. `4pi^(2)mv^(2)r^(2)`C. `2pi^(2)mv^(2)r^(2)`D. `pi^(2)mv^(2)r^(2)` |
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Answer» Correct Answer - C Given r is the outside radius of the dees v is the speed of the particle when travelling in a path of this radis and m is the mass of proton kinetic energy of particles accelerated in a cyclotorn `K=2pi^(2)mv^(2)r^(2)` |
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| 9. |
In a cyclotron, the angular frequency of a charged particle is independentA. massB. speedC. chargeD. magnetic field |
| Answer» Correct Answer - B | |
| 10. |
In a cyclotron, the charged particle cannot be accelerated to energies of the order of billion electron volt because if the speed of the particle is increasedA. the frequency of revolution is increasedB. the frequency of revolution is decreasedC. the frequency of a.c. source is decreasedD. the frequecny of a.c. source is increased |
| Answer» Correct Answer - B | |
| 11. |
In a cyclotron , the resonance condition is that the frequency of the charged particle is equal toA. the frequency of applied magnetic fieldB. the frequency of the applied magnetic fieldC. frequency of the applied magnetic field, and the frequency of the applied a.c. source.D. none of these |
| Answer» Correct Answer - B | |
| 12. |
A cyclotron is a device which generally used toA. accelerate -ve ionsB. accelerate +ve ionsC. accelerate both positive along a circular pathD. keep the charged particle along a circular path of constant radius |
| Answer» Correct Answer - B | |
| 13. |
The magnetic field at a point due to a current carrying conductor is directly proportional toA. resistance of the conductorB. thickness of the conductorC. distance from the conductorD. current flowing through the conductor |
| Answer» Correct Answer - D | |
| 14. |
The diagram given below represents magnetic field caused by a current-carrying conductor which is : A. a long straight wireB. a circular coilC. a solenoidD. a short straight wire |
| Answer» Correct Answer - B | |
| 15. |
A current carrying conductor placed in a uniform magnetic field , experienceA. a weak forceB. a strong forceC. a mechanical push on itD. an electrostatic imbalance |
| Answer» Correct Answer - C | |
| 16. |
In a cyclotron , the charged particles cannot be accelerated uptoA. KeVB. BeVC. MeVD. 500eV |
| Answer» Correct Answer - B | |
| 17. |
A neutorn a proton an electron and an `alpha` particle enter a region of uniform magnetic field with the same velocities the magnetic field is perpendicular and directed into the plane of the paper the tracks of the palrticles are labelled in the the electron follows the track A. DB. CC. BD. A |
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Answer» Correct Answer - A Radius `r=(mv)/(Bq)` r is least when `(m)q` is least `(m)/(q)` is least for electron so the electron follows the track D |
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| 18. |
A conductor of length 1m and carrying current of 1A is placed at an angle `45^@` to the magnetic field of 1 oersted. The force acting on the conductor isA. `(10^-4)/(sqrt(2))N`B. `(10^-4)/(sqrt(3))N`C. `(10^-2)/(sqrt(3))N`D. `(10^-2)/(sqrt(2))N` |
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Answer» Correct Answer - A `F=I b l sin theta = (10^-4)/(sqrt(2))N`. |
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| 19. |
Two particles X and Y having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii `R_1 and R_2,` respectively. The ratio of masses of X and Y isA. `((R_1)/(R_2))^2`B. `((R_2)/(R_1))^2`C. `(R_2)/(R_1)`D. `(R_1)/(R_2)` |
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Answer» Correct Answer - A `R=(mv)/(q B)=(sqrt(2mqV))/(q B)=(1)/(B) (sqrt(2mV))/(q)` For same charge and potential difference , `Rprop sqrt(m)rArr (R_1)/(R_2)=sqrt((m_1)/(m_2)` `therefore (m_1)/(m_2)=((R_1)/(R_2))^2` . |
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| 20. |
A long wire carries a steady curent . It is bent into a circle of one turn and the magnetic field at the centre of the coil is `B`. It is then bent into a circular loop of `n` turns. The magnetic field at the centre of the coil will beA. n BB. `n^2B`C. `2 n B`D. `2 n^2 B` |
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Answer» Correct Answer - B For same length , `B prop n^2` `therefore (B_2)/(B_1)=((n_2)/(n_1))^2` `B_2=((n)/(1))^2xxB=n^2B`. |
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| 21. |
The sensitivity of a moving coil galvanometer increases with the decrease inA. number of turnsB. area of the coilC. magnetic fieldD. None of these |
| Answer» Correct Answer - D | |
| 22. |
A striaight wire carries a current of 3 A calculate the magnitude of the magentic field at a point 15 cm away from the wireA. `2xx10^(-6)t`B. `4xx10^(-6)t`C. `3xx10^(-6)t`D. `8xx10^(-6)t` |
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Answer» Here current I =3.4 point where magnetic field is to be determined a =15 cm =015 m magnitude of magnetic field `B=(mu_(0)21)/(4pi a)` `=(10^(-)xx2xx3)/(0.15)=4xx10^(-6)T` |
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| 23. |
A magnetic needle is kept in a non uniform magnetic field . It experiencesA. a force and a torqueB. a force but not a torqueC. a torque but not a forceD. nither a force nor a torque |
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Answer» Correct Answer - B If the plane of magnetic field and the coil are hoizontal and vertical respectively then `theta=0`. Thus, torque on the coil is given by , `tau_(n)=n IAB cos theta= n IAB cos 0 = n IAB`. |
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| 24. |
Three moving coil galvanometer A,B and C are made of coils of three different material having torsional constrant `1.8xx10^(-8), 2.8xx10^(-8)` and `3.8xx10^(-8)` respectively if the three galvanometer are identical in all other respect then in which of the above cases sensitivity maximumA. AB. CC. BD. same in each case |
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Answer» Correct Answer - A If `theta` is the deflection in the galvanometer when current l is passed through it thenn current sensitivity `l_(s)=(theta)/(l)=(nBA)/(k)` where k be restoring torque per unit twist n be number of turns in the coil B is strenght of magnetic field in which coil is suspended A be area of coil sinc restoring torque per unit twist (trosional constant ) is minimum for galvanometer A hence it will be more sensitvie |
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| 25. |
If n is number of turns , B magnetic field strength , A area of coil and K torsional constant of suspension wire , then sensitivity is given byA. `(n AB)/(K)`B. `(K)/(n AB)`C. ` n ABK`D. `(n AB sin theta)/(K)` |
| Answer» Correct Answer - A | |
| 26. |
A charge q is moving with a velocity `v_(1)=1hati` m/s at a point in a magentic field and experiences a force `F=q[-hatj+1hatk]` N. If the charge is moving with a voloctiy `v_(2)=2hatj` m/s at the same point then it experiences a force `F_(2)=q(1hati-1hatk)` N. The magnetic induction B at that point isA. `(hatl+hatj+hatk)wb//m^(2)`B. `(hatl-hatj+hatk)wb//m^(2)`C. `(-hatl+hatj-hatk)wb//m^(2)`D. `(hatl+hatj-hatk)wb//m^(2)` |
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Answer» Correct Answer - A Let the magnetic field is, `B=B_(1)hati+B_(2)hatj+B_(3)hatk` Applying `F_(m)=q(vxxB)` two times, we have `q[-hatj+hatk]=q[(hati)xxB_(1)hati+B_(2)hatj+B_(3)hatk)]=q[B_(2)hatk-B_(3)hatj]` On comparing two sides, we get `B_(2)=1andB_(3)=1` Further, `q[hati-hatk]=q[(hatj)xxB_(1)hati+B_(3)hatk)]=q[-B_(1)hatk+B_(3)hati]` Agnin comparing we get `B_(1)=1andB_(3)=1` `:.B=(hati+hatj+hatk)Wb//m^(2)` |
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| 27. |
Three moving coil galvanometer A,B and C are made of coils of three different material having torsional constant `1.8xx10^(-8), 2.8xx10^(-8)` and `3.8xx10^(-8)` respectively if the three galvanometer are identical in all other respect then in which of the above cases sensitivity maximumA. AB. BC. CD. constant in each case |
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Answer» Correct Answer - A `S=(n AB)/(K) therefore S prop (1)/(K)`. Thus , for maximum sensitivity , torsional constant should be minimum. |
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| 28. |
Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potentail difference applied across them so that the magnetic field at their centres is the same?A. 3B. 4C. 6D. 2 |
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Answer» Correct Answer - B At the centre of coil-1 `B_(1)=(mu_(0))/(4pi)xx(2pii_(i))/(r_(1))" "......(i)` At the centre of coil-2 `B_(2)=(mu_(0))/(4pi)xx(2pii_(2))/(r_(2))" ".......(ii)` But `B_(1)=B_(2)` `:.(mu_(0))/(4pi)(2pii_(1))/(r_(1))=(mu_(0))/(4pi)(2pii_(2))/(r_(2))or(i_(1))/(r_(1))=(i_(2))/(r_(2))` As `r_(1)=2r_(2)` `:.(i_(1))/(2r_(2))=(i_(2))/(r_(2))ori_(1)=2i_(2)` Now, ratio of potential differences, `(V_(2))/V_(1)=(i_(2)xxr_(2))/(i_(1)xxr_(2))=(i_(2)xxr_(2))/(2i_(2)xx2r_(2))=(1)/(4)` `implies(V_(1))/(V_(2))=(4)/(1)` |
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| 29. |
Two concentric circular coils of ten turns each are situated in the same plane. Their radii are `20` and `40 cm` and they carry respectively `0.2` and `0.3` ampere current in opposite direction. The magnetic field in `Wb//m^(3)` at the centre isA. `mu_0//80`B. `7mu_0//80`C. `(5//4)mu_0`D. zero |
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Answer» Correct Answer - C `B=(mu_0nI)/(2pia)because Bprop(n I)/(a)` `B_1-B_2=(mu_0n)/(2)[(I_1)/(a_1)-(I_2)/(a_2)]` `=(10xx4pixx10^-7)/(2xx10^-2)[(0.2)/(20)-(0.3)/(40)]` `B_1-B_2=(4pixx10xx2xx10^-7)/(2xx10^-2xx800)=1.57xx10^-6=(5mu_0)/(4)T` . |
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| 30. |
The current measuring capacity of a galvanometer of resistance `50 Omega` is to be increased from x mA to `101 xxmA`.The shunt resistance isA. `0.5Omega`B. `0.25Omega`C. `1.5Omega`D. `0.35Omega` |
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Answer» Correct Answer - A `S=(G)/((n-1))=(50)/((101-1))=(50)/(100)=0.5Omega` . |
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| 31. |
The combined resistance of a galvanometer of resistance of `495` ohm and its shunt is `9.9 Omega` . The shunt resistance isA. `1.01Omega`B. `8.9Omega`C. `10.1Omega`D. `9.1Omega` |
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Answer» Correct Answer - C `R_A =(GS)/(S+G)` `9.9 S +495xx9.9 = 495 S S =(495xx9.9)/(485.1)=10.1Omega `. |
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| 32. |
A moving coil galvanometer has 100 turns and each turn has an area `2.0 cm^2`. The magnetic field produced by the magnet is `0.01 T`. The deflection in the coil is `0.05` radian when a current of `10 mA` is passed through it. Find the torsional constant of the suspension wire.A. `3.0xx10^(-4)Nm rad^(-1)`B. `4xxx10^(-5)Nm rad^(-1)`C. `5xx10^(-6) Nm rad^(-1)`D. `7xx10^(-7) Nm rad^(-1)` |
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Answer» We have , `i= (K)/(NAB) theta` `k=(NABi)/(theta)` Given number of turns N= 100 turns `area A= 2 cm^(2) =2xx10^(-4) m^(2)` magnetic field B= 0.01 T curent i=40 Ma `therefore k=4.0xx10^(-5) Nmrad^(-1)` |
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| 33. |
The frequency of direct current (d.c.) is :A. 0 HzB. 50 HzC. 60 HzD. 100 Hz |
| Answer» Correct Answer - A | |
| 34. |
A d.c. generator is based on the priciple of :A. electrochemical inductionB. electromagnetic inductionC. magnetic effect of currentD. heating effect of current |
| Answer» Correct Answer - B | |
| 35. |
A centre zero galvanometer is connected in series with a switch and a battery . When the switch is closed and opened periodically (nearly about 4 times/sec) its needleA. reads always zeroB. gives steady readingC. swings backward and forward across zeroD. swings backward and forward from zero about one side . |
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Answer» Correct Answer - C `tau_(n)= n IAB` `therefore I = (tau_n)/(n AB)=(18xx10^-5xx10^-2)/(60xx6xx10^-4xx500xx10^-4)` `=10^-3A` . |
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| 36. |
A current flows in a wire running between the S and N poles of a magnet lying horizontally as shown in Figure below : The force on the wire due to the magnet is directed :A. from N to SB. from S to NC. vertically downwardsD. vertically upwards |
| Answer» Correct Answer - C | |
| 37. |
An idduced emf is produced when a magnet is plunged into a coil. The magnitude of the induced emf is independent ofA. the speed with which the magnet is movedB. the number of turns of the coilC. the resistivity of turns of the coilD. the strength of the magnet |
| Answer» Correct Answer - C | |
| 38. |
The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The magnet was held stationery for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was :A. moving towards the solenoidB. moving into solenoidC. at rest inside the solenoidD. moving out of the solenoid |
| Answer» Correct Answer - D | |
| 39. |
When the switch S is closed in the figure given below, the pointer of the galvanometer moves to the right. If S is kept closed, will the pointer :A. return to zero ?B. stay over on the right ?C. move to the left and stay thereD. move to and fro until S is opened |
| Answer» Correct Answer - A | |
| 40. |
The pointer of a dead-beat galvanometer gives a steady deflection becauseA. eddy current are produced in tyh4e conducting frame over which the coil is woundB. its magnet is very strongC. its pointer is very lightD. its frame is made of ebonite |
| Answer» Correct Answer - A | |
| 41. |
A magnet attracts :A. plasticsB. any metalC. aluminiumD. iron and steel |
| Answer» Correct Answer - D | |
| 42. |
A plotting compass is placed near the south pole of a bar magnet. The pointer of plotting compass will :A. point away fromt the south poleB. point parallel to the south poleC. point towards the south poleD. point at right angles to the south pole |
| Answer» Correct Answer - C | |
| 43. |
The metallic pointer of a plotting compass gets deflected only when it is placed near a bar magnet because the pointer has :A. electromagnetismB. permanent magnetismC. induced megnetismD. ferromagnetism |
| Answer» Correct Answer - B | |
| 44. |
A galvanometer having a resistance of 20 ohm and capable of carrying a maximum current of 40 m A is to be converted into an ammeter of range `0-5` A. What is the resistance needed?A. `1.6Omega` in parallelB. `0.16Omega` in parallelC. `16.1Omega` in parallelD. None of these |
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Answer» Correct Answer - B `S=(I_g .G)/(I-I_g)` `S=(40xx10^-3xx20)/(5-0.040)=0.16Omega` . |
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| 45. |
A proton of energy `8 eV` is moving in a circular path in a uniform magnetic field. The energy of an alpha particle moving in the same magnetic field and along the same path will beA. 4eVB. 2eVC. 8eVD. 6eV |
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Answer» Correct Answer - C `E=(q^2B^2r^2)/(2m)` `therefore (E_alpha)/(E_P)=((q_alpha)/(q_P))^2 (m_p)/(m_alpha)=(4)/(1)xx(1)/(4)` `therefore E_alpha=E_p=8eV` |
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| 46. |
The cyclotron frequency of an electron gyrating in a magnetic field of 2 T is approximatelyA. 28 MHzB. 280 MHzC. 2.8 MHzD. 56 GHz |
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Answer» Correct Answer - D `v=(q B)/(2pi m)=(1.76cc10^11xx2)/(2xx3.14)=56GHz` |
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| 47. |
Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of `60^(@)` and `45^(@)` respectively. The ratio of the number of turns in the coils isA. `(4)/sqrt(3)`B. `sqrt(3+1)/(1)`C. `(sqrt(3)+1)/(sqrt(3-1)`D. `sqrt(3)/(1)` |
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Answer» Correct Answer - D In tangent galvanometer number of turns in coil is directly proportional to tangent of deflectoin for tangent galvanometer the number of turns `N prop tan theta` hence `(N_(1))/(N_(2))=(tan theta_(1))/(tan theta_(1))=(tan 60^(@))/(tan 45^(@))=sqrt(3)/(1)` |
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| 48. |
A charged particle of charge q moving with the velocity v, enters along the axis of a solenoid carrying a current. If B is the magnetic induction along the axis of the solenoid then the force acting on the charged particle will beA. q v BB. less than q v BC. zeroD. more than q v B |
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Answer» Correct Answer - C `F=qvBsintheta=qvBsin0=0`. |
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| 49. |
The accuracy of M.C.G. can be increased byA. taking large deflectionB. decreasing number of turnsC. decreasing area of the coilD. all of these |
| Answer» Correct Answer - D | |
| 50. |
The deflection produced per unit voltage in M.C.G. is calledA. charge sensitivityB. current sensitivityC. voltage sensitivityD. all of these |
| Answer» Correct Answer - C | |