Practice Test

Q1) Current is passed through a straight wire. The magnetic field established around it has its lines of force: Show Answer

Q2) There are two parallel wires attracting each other when same current is passed through them in the same direction, they are brought closer, the force of attraction shall : Show Answer

Q3) A certain length of wire carrying current is bent in the form of a coil of one turn. The same wire is then bent to form two turns of smaller radius. the magnetic induction at its center for the same current is : Show Answer

Q4) Two identical coils carrying same current have common center but have their planes at right angles to each other. If the field due to each is B, what is the resultant field ? Show Answer

Q5) A straight conductor is split into identical semi-circular turns by tearing it into two parts from within. A current enters at one end and after passing through two parts leaves at the other. The field at the center of the loop of radius r is : Show Answer

Q6) A straight wire carrying current and placed in the field experiences maximum force if : Show Answer

Q7) Particles carrying positive charge travel from sky towards earth. On entering the earth's field they get deflected towards : Show Answer

Q8) A uniform electric field and a uniform magnetic field are produced pointing in the same direction. An electron projected with a velocity pointing in the same direction will : Show Answer

Q9) A wire with current directed towards east is placed in magnetic field directed north, the force on the wire is : Show Answer

Q10) If a proton is projected perpendicular to the field with velocity v and an electron is projected along the field, which of the following holds ? Show Answer

Q11) A galvanometer having resistance of 20 ohm and capable of carrying a maximum current of 40 mA is to be converted into an ammeter of range 0-5 A, the galvanometer is to be converted into a voltmeter of range 5 volt, what is the resistance needed ? Show Answer

Q12) Magnetic induction in a long straight wire is : Show Answer

Q13) A strong magnetic field is applied on a stationary electron, then : Show Answer

Q14) The magnetic field at the center of a square loops of side L carrying a current I is : Show Answer

Q15) Magnetic induction due to long straight wire carrying current at a point on the wire itself is : Show Answer

Q16) If a long hollow copper pipe carries a direct current, the magnetic field associated with current will be : Show Answer

Q17) A current of 10 A is established in a long wire along the positive z-axis. The magnetic field at the point (1, 0, 0) meter is : Show Answer

Q18) P is a point mid-way between two infinite thin wires carrying current as shown, the net field at the point P is : Show Answer

Q19) Two long straight horizontal parallel wires, one above the other are separated by a distance 2a. If the wires carry equal currents in opposite direction, the magnitude of the field at a middle point between them is : Show Answer

Q20) A circular loop of radius R carrying a current I is placed in a uniform magnetic field with its plane perpendicular to B.The force on the loop is : Show Answer

Q21) A circular loop of radius R carrying a current I is placed in a uniform magnetic field with its plane perpendicular to B.The torque on the loop is : Show Answer

Q22) Weber ampere per meter is equal to : Show Answer

Q23) A moving coil voltmeter is generally used in the laboratory to measure the potential difference across a conductor of resistance r carrying current I. Voltmeter has resistance R and will measure the potential difference more correctly as : Show Answer

Q24) Fig. shows two long conducting wires placed at right angles. then carry currents as indicated. Assumes that 1A current in a long wire produces magnetic field B at a distance d from the wire. Then strength and direction of the field at the point X marked in the Fig. will be : Show Answer

Q25) No force is exerted by a magnetic field on Show Answer

Q26) What is the magnetic field in the empty space enclosed by toroidal solenoid of radius R ? Show Answer

Q27) Magnetic field due to a current carrying toroidal solenoid is independent of : Show Answer

Q28) A very long solenoid has 800 turns per meter length of the solenoid. A current of 1.6 ampere flows through it. Then, magnetic induction at the end of the solenoid on its axis is : Show Answer

Q29) A particle of charge q and mass m moving with a velocity v along the x-axis enters the region x > 0 with uniform magnetic field B along the z-direction. the particle will penetrate in this region in the x-direction upto a distance d equal to : Show Answer

Q30) Two parallel beams of electrons moving in the same direction, produce a mutual force of : Show Answer

Q31) Two ions have equal masses but one is singly ionized and the other is doubly ionized. They are projected from the same place in a uniform magnetic field with same velocity perpendicular to the field. Show Answer

Q32) A charged particle is projected into a uniform magnetic field with velocity perpendicular to direction of the field. which of the following quantities of particle will not change ? Show Answer

Q33) The magnetic induction at a point O, distance r from the corner of an infinitely long wire carrying current I and bent at right angle is : Show Answer

Q34) Two particles each of mass m and charge q are attached to the two ends of a light rod of length 2R. The rod is rotated at the constant angular speed about a perpendicular axis passing through its center. The radio of the magnitude of the magnetic moment of the system and its angular momentum about the center of the rod is : Show Answer

Q35) A long metal cylinder of radius r has a current I flowing through it. The magnetic induction B will vary with distance from the center as shown in : Show Answer

Q36) A long hollow metal cylinder of radius R has a current I flowing through it. The magnetic induction B will vary with distance from the center as shown in : Show Answer

Q37) A charge moves in a circle perpendicular to a magnetic field. The time period of revolution is independent of : Show Answer

Q38) An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field of B at the center of the circle. The radius of the circle is proportional to : Show Answer

Q39) Which of the following graphs correctly represents the variation of energy density u near the mid-point of a long current carrying conductor with magnetic field B ? Show Answer

Q40) An electron is moving along positive x-axis. To get it moving on an anti-clockwise circular path in x-y plane, a magnetic field is applied : Show Answer

Q41) A conductor of length 1 m carrying a current of 1 A is placed parallel to magnetic field 1 gauss. The magnetic force acting on the conductor is : Show Answer

Q42) A current - carrying loop is placed in a uniform magnetic field. The torque acting on it does not depend upon : Show Answer

Q43) Two identical long solenoids carry the same constant current. When they are very far apart, the flux density at the center of each end of each solenoid is B. The solenoids are now arranged coaxially end to end with the current in each flowing in the same sense. The flux density on the axis in the region of contact is : Show Answer

Q44) A current carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire : Show Answer

Q45) Which of the following particles will experience maximum magnetic force ( magnetic ) when projected with the same velocity perpendicular to a magnetic field ? Show Answer

Q46) A charged particle is situated in a region of space and it experiences a force only when it is in motion. It can be deduced that the region encloses : Show Answer

Q47) An electric current I enters and leaves a uniform circular wire radius a through diametrically opposite points. A charged particle q moving along the axis of a circular wire passes through its center at speed v. The magnetic force acting on the particle when it passes through the center has a magnitude : Show Answer

Q48) A proton beam is going from north to south and an electron beam is going from south to north. Neglecting the earth's magnetic field, the electron beam will be deflected : Show Answer

Q49) A rectangular coil of area A of N turns has a current I flowing in clockwise direction when looked at from above. The magnetic moment associated with it : Show Answer

Q50) A current is flowing north along a power line. The direction of magnetic field above it, neglecting the earth's field is : Show Answer

Q51) Two long thin wires distant a apart exert a force F on one another when current through each wire is I. The distance between the wires is doubled and the current is decreased to I/3. The force they exert on another, now is : Show Answer

Q52) The pole pieces of the magnetic field whose direction is perpendicular to the velocity of the electron. Then : Show Answer

Q53) A current carrying small loop behaves like a small magnet. If A be its area and M its magnetic moment, the current in the loop will be : Show Answer

Q54) A circular loop carrying a current is replaced by an equivalent magnetic dipole. A point on the axis of the loop is now on : Show Answer

Q55) Two wires of equal length are placed perpendicular to the plane of paper at a distance of 5 cm from each other. If the currents flowing in first and second wires are 2A and 5A respectively in opposite directions, then the resultant magnetic field at mid-point of both the wires is : Show Answer

Q56) A length L of wire carries a steady current I. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the center caused by the same current is : Show Answer

Q57) A current of 10 ampere is flowing in a wire of length 1.5 m. A force of 15 newton acts on it when it is placed in a uniform magnetic field of 12 tesla. The angle between the magnetic field and the direction of the current is : Show Answer

Q58) An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction, then : Show Answer

Q59) Two long parallel wires are at a distance 2d apart. They carry steady equal currents flowing out of the plane of the paper, as shown in fig. The variation of the magnetic field B along the line XX' is given by : Show Answer

Q60) Two long parallel wires at distance d apart carry currents of 1 A and 3 A in the same direction. The wire carrying 1 A current lies to the left of the other wire. The points at which their magnetic fields cancel are located at : Show Answer

Q61) A closely wound flat circular coil of 25 turns of wire has diameter of 10 cm and carries a current of 4 ampere. Determine the flux density at the center of coil. Show Answer

Q62) A long vertical wire in which a current produces a neutral point with the earth's magnetic field at a distance of 5 cm from the wire. If the horizontal component of the earth's magnetic induction is 0.18 gauss, then the current in the wire is : Show Answer

Q63) A coil having N turns in wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the center is : Show Answer

Q64) The magnetic field of a certain length of wire for single turn coil at its center is B. Its value for two turns coil for the same wire is : Show Answer

Q65) A charged particle moves in a circular path in a uniform magnetic field. The radius of circular path is R. When energy of particle is doubled, then new radius will be : Show Answer

Q66) A particle of mass m and charge q moves with a constant velocity v along the positive x direction. It enters a region containing a uniform magnetic field B directed along the negative z direction, extending from x=a to x =b. The minimum value of v required so that the particle can just enter the region x > b is : Show Answer

Q67) An electron is travelling along the x-direction. It is encounters a magnetic field in the y-direction. Its subsequent motion will be : Show Answer

Q68) When a charged particle moves perpendicular to a magnetic field, then : Show Answer

Q69) A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, then new value of the magnetic field is : Show Answer

Q70) A wire of certain length carries a steady current. It is first bent to form a circular coil of one turn. The same wire is next bent to form a circular coil of three turns. The ratio of magnetic inductions at the center of the coil in the two cases is : Show Answer

Q71) The magnetic field (B) due to straight conductor of uniform cross-section of radius (a) and carrying a steady current (I) is represented by : Show Answer

Q72) Two parallel beams of positions moving in the same direction will : Show Answer

Q73) A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from center of the coil, such that r > > R varies : Show Answer

Q74) The magnetic moment of a current (I) carrying circular coil of radius (r) and number of turns (n) varies as : Show Answer

Q75) The cyclotron frequency of an electron gyrating in a magnetic field of 1 T is : Show Answer

Q76) A circular radius 'a' carries a current I. The magnetic induction at its center O due to the current is B. The distance from O of a point on the axis where the induction is B/8 is : Show Answer

Q77) The straight of the magnetic field at a point r near a long straight current carrying wire is B. The field at a distance r/2 will be : Show Answer

Q78) Electron of mass m and charge e is travelling with a speed v along the circular path of radius r at right angles of a uniform magnetic field B. If the speed of the electron is doubled and the magnetic field is halved the resulting path would have a radius : Show Answer

Q79) A particle having charge 'q' enters a magnetic field perpendicular to it, then which of the following is true ? Show Answer

Q80) A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance. The magnetic field at P is : Show Answer

Q81) Two circular coils 1 and 2 are made from the same wire but radius of 1st coil is twice that of 2nd coil. What potential difference in volts should be applied across them so that the magnetic field at their centers is same ? Show Answer

Q82) A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move Show Answer

Q83) Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed V. The time period of the motion : Show Answer

Q84) For the magnetic field due to a small element of a current carrying conductor at a point to be maximum, the angle between the element and the line joining the element to the given point must be Show Answer

Q85) The direction of magnetic field produced by a linear current carrying conductor is given by Show Answer

Q86) A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter and carrying the same current. What is the strength of the magnetic field at the same distance from the wire? Show Answer

Q87) Two current carrying circular coils A and B, having the same number of turns are connected in series. What is the ratio of the magnetic inductions produced at their centres, if the diameters of A and B are 10 cm and 20 cm respectively? Show Answer

Q88) When a battery is connected to the two ends of a diagonal of a square conductor frame of side 'a', the magnitude of magnetic field at the centre will be Show Answer

Q89) What is the magnetic induction at the centre of a circular coil of 10 turns, each of radius 5 cm and carrying a current of 5 A? Show Answer

Q90) A particle having a charge 100 times that of an electron is revolting in a circular path of radius 0.8 m with one rotation per sec. What is the magnetic field produced at the centre of the circle? Show Answer

Q91) The magnetic field at the centre of a current carrying circular coil of area A is B. What is the magnetic moment of the coil? Show Answer

Q92) A long wire carries a steady current. 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. What will be the magnetic field at the centre of the coll? Show Answer

Q93) A wire of length 1 m is kept perpendicular to a magnetic field of 0.98 T. What is the current flowing through the wire if a force of 1 kg weight acts on the wire? Show Answer

Q94) A straight wire of length 0.5 m and carrying a current of 1.2 A is placed in uniform magnetic field of induction 2 T. The magnetic field is perpendicular to the length of the wire. What is the force acting on the wire? Show Answer

Q95) An electron is projected along the axis of a circular conductor carrying some current. Electron will experience Show Answer

Q96) A charged particle moves through a magnetic field perpendicular to its direction. Then Show Answer

Q97) Two long parallel wires are at a distance of 1 m. Both of them carry one ampere of current in the same direction. What is the force of attraction per unit length between the two wires? Show Answer

Q98) Two parallel beams of positrons moving in the same direction will Show Answer

Q99) If the distance between two current-carrying parallel wires is halved, then the force between them is Show Answer

Q100) Two parallel wires of equal lengths are placed at a distance of 4 m from each other. The currents flowing in the first and second wires are 3 A and 5 A respectively in opposite directions. What is the resultant magnetic field at the mid- point of both the wires? Show Answer

Q101) Two long straight wires are arranged parallel to each other and are kept 10 cm apart in vacuum. They carry currents of 5A and 10A respectively in the same direction. What is the magnetic force on a length of 20 cm of either wire? Show Answer

Q102) If a current is passed through a spring then the spring will Show Answer

Q103) Beams of electrons and protons move parallel to each other in the same direction. They will Show Answer

Q104) A wire of length L carries a steady current. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre produced by the same current will be Show Answer

Q105) A current carrying coil is kept in a uniform magnetic field. The coil will orient itself so that its plane becomes Show Answer

Q106) A circular coil of 20 turns each of radius 10 cm and carrying a current of 5 A is placed in a uniform magnetic field of induction 0.10 T normal to the plane of the coil. What is torque acting on the coil? Show Answer

Q107) A straight wire of length 1 m, and carrying a current of 1.8 A, is placed in a uniform magnetic field of induction 2 T. If the magnetic field is perpendicular to the length of the wire, then the force acting on the wire is Show Answer

Q108) A charged particle of charge q moving with a 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 be Show Answer

Q109) A long solenoid carrying a current produces a magnetic field B along its axis. If the number of turns per cm is tripled and the current is halved, then the new value of the magnetic field will be Show Answer

Q110) A straight wire of diameter 0.4 mm carrying a current of 2 A is replaced by another wire of 0.8 mm diameter and carrying the same current. The magnetic field at the same distance from the wire is Show Answer

Q111) A long solenoid has 800 turns per metre length of solenoid. What is the magnetic induction at the end of the solenoid if it carries a current of 2.5 A? Show Answer

Q112) A solenoid is 2 m long and 4 cm in diameter. It has 4 layers of windings of 1000 turns each and carries a current of 5 A. What is the magnetic field at the centre of the solenoid? Show Answer

Q113) A current of 2 A flows in an air core solenoid of length 1 m and number of turns 1000. What is the magnetic flux density inside the solenoid? Show Answer

Q114) A long solenoid of length L has a mean diameter D. It has n layers of windings, each of N turns. If it carries a current I, the magnetic field at its centre will be Show Answer

Q115) The magnetic induction due to toroidal solenoid is independent of Show Answer

Q116) A current of 1.6 A flows through a long solenoid, having 8 turns/cm. The magnetic induction at the end of the solenoid along its axis is Show Answer

Q117) Toroid is a Show Answer

Q118) If a current is passed in a spring then Show Answer

Q119) A winding wire which is used to prepare a solenoid of length 80 cm can bear a maximum current of 10 A. The cross sectional radius of the solenoid is 3 cm. What should be the length of the winding wire if a magnetic field of 0.2 T is to be produced at the centre of the solenoid along its axis? Show Answer

Q120) The cyclotron frequency of an electron rotating in a magnetic field of 1 T is approximately equal to Show Answer

Q121) A proton of energy E is moving in a circular path in a uniform magnetic field. The energy of an a particle moving in the same magnetic field and along the same path will be equal to Show Answer

Q122) A proton describes a circular path of radius 5 cm in a transverse magnetic field. If the speed of the proton is doubled, then the radius of the circular path will be Show Answer

Q123) Protons are accelerated in a cyclotron where the applied magnetic field is 2T and the P.D. across the dees is 100 KV. How many revolutions the proton has to complete to acquire a K.E. of 20 MeV? Show Answer

Q124) A particle having a charge 100 times that of an electron is revolving in a circular path of radius 0.4 m, with 1 rev/s. What is the magnitude of the magnetic field produced at its centre? Show Answer

Q125) In a cyclotron a deuteron gains maximum energy of 30 MeV. What is the maximum energy gained by a proton for the same cyclotron setting? Show Answer

Q126) A charged particle moving in a magnetic field along a circular path of radius r passes through a very thin lead sheet and thereby loses half its kinetic energy. What will be the radius of its new circular path? Show Answer

Q127) A deutron of kinetic energy 50 KeV is describing a circular orbit of radius 0.5 m in a plane perpendicular to a magnetic field B. What is the kinetic energy of a proton describing a circular orbit of radius 0.5 m in the same plane with the same B? Show Answer