Practice Test


1) A particle moving in a magnetic field increases its velocity then its radius of the circle


2) Two charged particles are projected into a region in which a magnetic field is perpendicular to their velocities. After they enter the magnetic field, you can conclude that


3) A charge is fired through a magnetic field. The force acting on the charge is maximum when the angle between the direction of motion of charge and the magnetic field is


4) The field due to a long straight wire carrying a current I is proportional to


5) The forces existing between two parallel current carrying conductors is F. If the current in each conductor is doubled, then the value of force will be


6) The force between two parallel current carrying wires is independent of


7) An electron and a proton have equal kinetic energies. They enter in a magnetic field perpendicular to B, then


8) The ratio of magnetism potentials due to magnetic dipole in the end on position to that in broad side on position for the same distance from it is


9) A long copper tube of inner radius R carries a current i. The magnetic field B inside the tube is


10) A wire of length l is bent into a circular loop of radius R and carries a current I. The magnetic field at the centre of the loop is B. The same wire is now bent into a double loop of equal radii. If both loop carry the same current I and it is in the same direction, the magnetic field at the centre of the double loop will be


11) Gauss is unit of which quantity


12) A bar magnet is cut into two equal halves by a plane parallel to the magnetic axis. Of the following physical quantities, the one which remains unchanged is


13) An electric current passes through a long straight copper wire. At a distance 5 cm from the straight wire, the magnetic field is B. The magnetic field at 20 cm from the straight wire would be


14) The areas of cross-section of three magnets of same length area A,2 A and 6A respectively. The ratio of their magnetic moments will be


15) 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. The magnetic field at the centre of the coil will be


16) A proton a mass m and charge +e is moving in a circular orbit in a magnetic field with energy 1 MeV. What should be the energy of α-particle (mass =4m and charge =+2e), so that it can revolve in the path of same radius


17) The magnetic field at the point of intersection of diagonals of a square loop of side L carrying a current I is


18) A current i is passing through a straight conductor of infinite length. The magnetic field at a point situated at a distance R from the conductor is


19) A current of 1 ampere is passed through a straight wire of length 2.0 metres. The magnetic field at a point in air at a distance of 3 metres from either end of wire and lying on the axis of wire will be


20) An electron and proton having same kinetic energy enter into magnetic field perpendicular to it. Then


21) An alternating electric field, of frequency v, is applied across the dees (radius =R) of a cyclotron that is being used to accelerated protons (mass =m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by


22) A steady electric current is flowing through a cylindrical conductor


23) A beam of protons is moving parallel to a beam of electrons. Both the beams will tend to


24) A wire of length l metre carrying a current i ampere is bent in the form of a coil having two turns. Its magnitude of magnetic moment will be


25) A length of wire carries a steady current. It is bent first to form a circular 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 caused by the same current is


26) 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


27) Two very long, straight, parallel wires carry steady current i and-i resepectively. The distance between the wires is d. At a certain instant of time, a point charge q is at a point equidistant from the two wires, in the plane of the wires. Its instantaneous magnitude of the force due to the magnetic field acting on the charge at this instant is


28) The magnetic field due to a straight conductor of uniform cross section of radius a and carrying a steady current is represented by


29) The magnetic field at the point of intersection of diagonals of a square wire loop of side L carrying a current I is


30) Magnetic dipole moment of a rectangular loop is


31) A cylindrical conductor of radius ‘R’ carries a current ‘i’. The value of magnetic field at a point which is R/4 distance inside from the surface is 10T. Find the value of magnetic field at point which is 4R distance outside from the surface


32) The magnetic dipole moment of a current loop is independent of


33) Two circular coils are made of two identical wires of same length. If the number of turns of two coils are 4 and 2, then the ratio of magnetic induction at centres will be zero


34) Magnetic field at the centre of a circular coil of radius Rdue to i flowing through it is B. The magnetic field at a point along the axis at distance R from the centre is


35) Which of the field pattern given in the figure is valid for electric field as well as for magnetic field?


36) A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its plane becomes


37) An electron is projected along the axis of a circular conductor carrying some current. Electron will experience force


38) If the current is doubled, the deflection is also doubled in


39) A charge moves in a circle perpendicular to a magnetic field. The time period of revolution is independent of


40) A stream of electrons is projected horizontally to the right. A straight conductor carrying a current is supported parallel to electron stream and above it. If the current in the conductor is from left to right, then what will be the effect on electron stream?


41) A circular coil A of radius r carries current i. Another circular coil B of radius 2r carries current of i. The magnetic fields at the centres of the circular coils are in the ratio of


42) A charge q is moving in a magnetic field then the magnetic force does not depend upon


43) A current carrying circular loop is freely suspended by a long thread. The plane of the loop will point in the direction


44) A current is flowing through a thin cylindrical shell of radius R. If energy density in the medium, due to magnetic field, at a distance r from axis of the shell is equal to U then which of the following graphs is correct


45) An electron of charge e moves with a constant speed v along a circle of radius r. Its magnetic moment will be


46) Uniform magnetic B is directed vertically upwards and 3 wires of equal length L, carrying equal current i are lying in a horizontal plane such that the first one is along north, second one along north-east and the third one at 60° north of east. Force exerted by magnetic field B on them is


47) There are 50 turns of a wire in every cm length of a long solenoid. If 4 ampere current is flowing in the solenoid, the approximate value of magnetic field along its axis at an internal point and at one end will be respectively


48) A current of 5 ampere is flowing in a wire of length 1.5 metres. A force of 7.5 N acts on it when it is placed in a uniform magnetic field of 2 tesla. The angle between the magnetic field and the direction of the current is


49) Two parallel wires carrying currents in the same direction attract each other because of


50) A proton (or charged particle) moving with velocity v is acted upon by electric field E and magnetic field B. The proton will move undeflected if


51) A neutral point is obtained at the centre of a vertical circular coil carrying current. The angle between the plane of the coil and the magnetic meridian is


52) The deflection in a galvanometer falls from 50 division to 20 when a 12 Ω shunt is applied. The galvanometer resistance is


53) 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 three loops of smaller radius. The magnetic field at the centre caused by the same current is


54) A long thin hollow metallic cylinder of radius ‘R’ has a current i ampere. The magnetic induction ‘B’-away from the axis at a distance r from the axis varies as shown in


55) 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 the centre of the coil, such that r>>R, varies as


56) A wire of length L is bent in the form of a circular coil and current i is passed through it. If this coil is placed in a magnetic field then the torque acting on the coil will be maximum when the number of turns is


57) A charge moving with velocity v in X-direction is subjected to a field of magnetic induction in the negative X-direction. As a result, the charge will


58) Two parallel beams of protons and electrons, carrying equal currents are fixed at a separation d. The protons and electrons move in opposite directions. P is a point on a line joining the beams, at a distance x from any one beam. The magnetic field at P is B. If B is plotted against x, which of the following best represents the resulting curve


59) Positively charged particles are projected into a magnetic field. If the direction of the magnetic field is along the direction of motion of the charge particles, the particles get


60) The deflection in moving coil galvanometer is reduced to half, when it is shunted with a 40 Ω coil. The resistance of the galvanometer is


61) In a cyclotron, the angular frequency of a charged particle is independent of


62) A solenoid of 1.5 m length and 4.0 cm diameter has 10 turns per cm. A current of 5 A is flowing through it. The magnetic field induction at axis inside the solenoid is


63) If a copper rod carries a direct current, the magnetic field associated with the current will be


64) The coil of a moving coil galvanometer is wound over a metal frame in order to


65) An electron and a proton are projected at right angles to a uniform magnetic field with the same kinetic energy. Then


66) An electron and a proton with equal momentum enter perpendicularly into a uniform magnetic field, then


67) A circular coil is in y-z plane with centre at origin. The coil is carrying a constant current. Assuming direction of magnetic field at x=-25 cm to be positive direction of magnetic field, which of the following graphs shows variation of magnetic field along x-axis


68) The helium nucleus makes a full rotation in a circle of radius 0.8 m in 2 s. The value of the magnetic field induction B in tesla at the centre of circle will be


69) The unit of electric current “ampere” is the current which when flowing through each of two parallel wires spaced 1 m apart in vacuum and of infinite length will give rise to a force between them equal to


70) An electron rotates about a proton, the induced magnetic field is 14T at the centre, find out the angular velocity of electron if radius of rotation is 0.5 nm


71) The electrons in the beam of television tube move horizontally form south to north. The vertical component of the earth’s magnetic field points down. The electron is deflected towards


72) An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has a magnitude of


73) The magnetic field at the centre of a current carrying circular loop is B. If the radius of the loop is doubled, keeping the current same, the magnetic field at the centre of the loop would be


74) A current i flows along the length of an infinitely long, straight, thin-walled pipe. Then


75) The magnetic field lines due to a bar magnet are correctly shown in


76) A proton (mass m and charge +e) and an α-particle (mass 4m and charge +2e) are projected with the same kinetic energy at right angles to the uniform magnetic field. Which one of the following statements will be true


77) Two particles A and B having equal charges +6C, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii 2cm and 3cm respectively. The ratio of mass of A to that of B is


78) A current I flow in an infinitely long wire cross-section in the form of a semi-circular ring of radius R. The magnitude of the magnetic induction along its axis is


79) An electron is revolving around a proton in a circular path of diameter 0.1 nm. It produces a magnetic field
14 T at a proton. Then the angular speed of the electron is


80) 1A current flows through an infinitely long straight wire. The magnetic field produced at a point 1 metre away from it is


81) A magnetic needle lying parallel to a magnetic field required W units of work to turn it through 60°. The torque required to maintain the needle in this position will be


82) Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to the magnetic field?


83) An electron moving with a uniform velocity along the positive x-direction enters a magnetic field directed along the positive y-direction. The force on the electron is directed along


84) A solenoid consists of 100 turns of wire and has a length of 10.0 cm. The magnetic field inside the solenoid when it carries a current of 0.500 A will be


85) The magnetic field on the axis of a long solenoid having n turns per unit length and carrying a current i is


86) Potential energy of a bar magnet of magnetic moment M placed in a magnetic field of induction B such that it makes an angle θ with the direction of B is


87) An electron is moving in the north direction. It experiences a force in vertically upward direction. The magnetic field at the position of the electron is in the direction of


88) The magnetic moment of a circular coil carrying current is


89) Two magnets have the same length and the same pole strength. But one of the magnets has a small hole at its center. Then


90) A rectangular coil 20 cm×20 cm has 100 turns and carries a current of 1 A. It is placed in a uniform magnetic field B=0.5 T with the direction of magnetic field parallel to the plane of the coil. The magnitude of the torque required to hold this coil in this position is


91) A vertical wire carrying a current in the upward direction is placed in horizontal magnetic field directed towards north. The wire will experience a force directed towards


92) Two long parallel wires carry equal current i flowing in the same direction area at a distance 2d apart. The
magnetic field B at a point lying on the perpendicular line joining the wires and a distance x from the
midpoint is


93) A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in x-z plane. If the current in the loop is i. The resultant magnetic field due to the two semicircular part at their common centre is


94) Two circular coils mounted parallel to each other on the same axis carry steady current.If an observer between the coil reports that one coil is carrying a counter clockwise current i1 and while other is carrying i2 current ,between two coil and there is,


95) A current carrying loop is free to turn in a uniform magnetic field. The loop will them come into equilibrium when its plane is inclined at


96) A circular coil having N turns is made from a wire of length L meter. If a current I ampere is passed through it and is placed in a magnetic field of Btesla, the maximum torque on it is


97) The strength of the magnetic field around a long straight wire, carrying current, is


98) Motion of a moving electron is not affected by


99) An electron and a proton travel with equal speed in the same direction at 90° to a uniform magnetic field as this is switched on. They experience forces which are initially


100) At a distance of 10 cm from a long straight wire carrying current, the magnetic field is 0.04 T. At the distance of 40 cm, the magnetic field will be


101) If a current is passed in a spring, it


102) A uniform magnetic field acts at right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2 cm. If the speed of the electrons is doubled, then the radius of the circular path will be


103) 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


104) A chare q coulomb moves in a circle at n revolutions per second and the radius of the circle is r metre.
Then the magnetic field at the centre of the circle is


105) A metal wire of mass m slides without friction on two rails placed at a distance l aprt. The track lies in a uniform vertical magnetic field B. A constant current i flows along the rails across the wire and brack down the other rail. The acceleration of the wire is


106) If a proton, deuteron and α-particle on being accelerated by the same potential difference enters perpendicular to the magnetic field, then the ratio of their kinetic energies is


107) A uniform electric field and a uniform magnetic field exist in a region in the same direction. An electron is
projected with a velocity pointed in the same direction. Then the electron will


108) A solenoid 1.5 m long and 0.4 cm in diameter possesses 10 turns/cm length. A current of 5 A falls through
it. The magnetic field at the axis inside the solenoid is


109) Proton and α-particle are projected perpendicularly in a magnetic field, if both move in a circular path with same speed. Then ratio of their radii is


110) The oscillating frequency of a cyclotron is 10 MHz. If the radius of its Dees is 0.5 m, then kinetic energy of a proton, which is accelerated by the cyclotron is


111) An α particle and a proton travel with same velocity in a magnetic field perpendicular to the direction of their velocities. Find the ratio of the radii of their circular path


112) A circular coil of 20 turns and radius 10 cm is placed in uniform magnetic field of 0.10 T normal to the plane of the coil. If the current in coil is 5 A, then the torque acting on the coil will be


113) A charged particle is moving in a uniform magnetic field in a circular path. Radius of circular path is R. When energy of particle is doubled, then new radius will be


114) A charged particle is projected in a plane perpendicular to a uniform magnetic field. The area bounded by the path described by the particle is proportional to


115) A circular loop and a square loop are formed from the same wire and the same current is passed through them. Find the ratio of their dipole moments.


116) A proton, a deuteron and an alpha particle with the same kinetic energy enter a region of uniform magnetic field B at right angles to the field. The ratio of the radii of their circular paths is


117) A current carrying conductor produces


118) A current carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire


119) A long hollow copper tube carries a current I. Then which of the following will be true?


120) A straight wire carrying a current 10 A is bent into a semicircular arc of radius 5 cm. The magnitude of magnetic field at the centre is


121) The magnetic field normal to the plane of a wire of n turns and radius r which carries a current i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the magnetic field at the centre by the fraction


122) An electron is moving on a circular path of radius r with speed v in a transverse magnetic field B.e/m for it will be


123) Two free parallel wires carrying currents in the opposite directions


124) The magnetic flux density B at a distance r from a long straight rod carrying a steady current varies with r as shown in figure.


125) A charge particle of mass m and charge q enters a region of uniform magnetic field B perpendicular of its velocity v. The particle initially at rest was accelerated by a potential difference V (volts) before it entered the region of magnetic field. What is the diameter of the circular path followed by the charged particle in the region of magnetic field?


126) A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in a uniform magnetic field of induction 2 tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is


127) A proton, a deutron and a α- particle enter a magnetic field perpendicular to field with same velocity. What is the ratio of the radii of circular paths?


128) A proton of energy 200 MeV enters the magnetic field of 5 T. If direction of field is from south to north and motion is upward, the force acting on it will be


129) A current i flows in a circular coil of radius r. If the coil is placed in a uniform magnetic field B with its plane parallel to the field, magnitude of the torque that acts on the coil is


130) If a current is passed in a spring, it


131) The radius of a circular loop is r and a current i is flowing in it. The equivalent magnetic moment will be


132) A coil carrying a heavy current and having large number of turns is mounted in a N-S vertical plane and a current flows in clockwise direction. A small magnetic needle at its centre will have its north pole in


133) A moving charge will gain energy due to the application of


134) A straight wire of mass 200 g and length 1.5 m carries a current of 2 A. It is suspended in mid-air by a uniform horizontal magnetic field B. The magnitude of B (in tesla) is


135) A long hollow copper tube carries a current I. Then which of the following will be true?


136) An electron enters a region where electrostatic field is 20N/C and magnetic field is 5T. If electron passes undeflected through the region, the velocity of electron will be


137) Magnetic field intensity at the centre of coil of 50 turns, radius 0.5 m and carrying a current of 2 A is


138) An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the lengths and radii of the wires are in the ratio of 4/3 and 2/3, then the ratio of the currents passing through the wire will be


139) When a charged particle enters a uniform magnetic field, its kinetic energy


140) The force on a charged particle moving with a velocity v in a magnetic field B is not


141) A long, straight, solid metal wire of radius 2 mm carries a current uniformly distributed over its circular cross-section. The magnetic field induction at a distance 2 mm from its axis is B. Then the magnetic field induction at distance 1 mm from axis will be


142) When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre will become


143) A straight wire of mass 200 g and length 1.5 m carries a current of 2 A. It is suspended in mid-air by a uniform horizontal magnetic field B. The magnitude of B (in tesla) is


144) A horizontal metal wire is carrying an electric current from the north to the south. Using a uniform magnetic field, it is to be prevented from falling under gravity. The direction of this magnetic field should be towards the


145) The cyclotron frequency of an electron grating in a magnetic field of 1 T is approximately


146) A cable carrying a direct current is burried in a wall which stands in a north-south plane. A horizontal compass needle on the west side of the wall is found to point towards south instead of north. The coil is laid


147) An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true?


148) Radius of curvature of path of the charged particle in the uniform magnetic field is directly proportional to


149) The electron movie toward the east enters a magnetic field directed towards the north.The force on the electric field will be directed


150) Four charged particles are projected perpendicularly into the magnetic field with equal. Which will have minimum frequency?


151) An electron moving around the nucleus with an angular momentum l has a magnetic moment


152) A uniform electric field and a uniform magnetic field are produced, pointing in the same direction. If an electron is projected with its velocity pointing in the same direction


153) Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance 5 m between them. If P and Q carry current of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half way between the wires is


154) A moving coil galvanometer gives full scale deflection, when a current of 0.005 A is passed through its coil. It is converted into a voltmeter reading upto 5V by using an external resistance of 975 Ω. What is the resistance of the galvanometer coil?


155) Two long wires are hanging freely. They are joined first in parallel and then in series and then are connected with a battery. In both cases, which type of force acts between the two wires


156) In order to increase the sensitivity of a moving coil galvanometer, one should decrease


157) A current i A flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube is


158) A wire of length 2 m carrying a current of 1 A is bent to form a circle, the magnetic moment of the coil is


159) A loosely wound helix made of stiff wire is mounted vertically with the lower end just touching a dish of mercury. When a current from a battery is started in the coil through the mercury


160) The resultant magnetic moment of neon atom will be


161) If two parallel wires carry current in opposite directions


162) A very high magnetic field is applied to stationary charge then magnetic charge experiences


163) A charged particle enters in a magnetic field whose direction is parallel to velocity of the particle, then the speed of this particle


164) A proton and a deuteron with the same initial kinetic energy enter a magnetic field in a direction perpendicular to the direction of the field. The ration of the radii of the circular trajectories described by them is


165) A straight wire carrying current i,is turned into a circular loops .If the magnitude of magnetic movement associate with in MKS unit is M the length of wire will be


166) In a current carrying long solenoid ,the field produces does not depend upon


167) The Magnetic induction of the centre of current carrying radius r,is


168) One Tesla is equal to


169) Maximum kinetic energy of the positive ion in the cyclotron is


170) Which of the following graph represents the variation of magnetic flux density B with distance r for a straight long wire carrying an electric current?


171) The direction of induced magnetic field dB due to current element i dL ,at a point of distance r from it ,when a current i passes through a long conductor is in the direction


172) 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


173) A small circular flexible loop of wire of radius r carries a current I. It is placed in a uniform magnetic field B. The tension in the loop will be doubled if


174) A current carrying rectangular coil is placed in a uniform magnetic field. In which orientation, the coil will not tend to rotate


175) The dimension of the magnetic field intensity B is


176) Biot-Savart’s law may be represented in vector form as


177) A current carrying loop is placed in uniform magnetic field.the torque acting on it does not depend upon


178) Which of the following graphs represent variation of magnetic field B with distance r for a straight long wire carrying current?


179) The ratio of magnetic field and magnetic moment at the centre of current carrying circular loop is x.when the both the current and radius is doubled then the ratio will be


180) A particle is moving in a uniform magnetic field, then


181) A large magnet is broken into two pieces so that their lengths are in the 2:1. The pole strengths of the two pieces will have ratio


182) Consider the following statement regarding a charged in a particle.
I) starting with zero velocity ,it accelerate in direction perpendicular to its magnetic field .
II) While deflecting to its magnetic field ,its energy gradually increases
III)only the component of magnetic field perpendicular to the direction of motion of the charged particle is effective deflecting it
IV)Direction of deflecting force on moving charge particle is perpendicular to its velocity of these statement


183) Toroid is


184) Two long parallel wires are at a distance 2d apart. They carry steady equal current flowing out of the plane of the paper as shown. The variation of the magnetic field along the line XX'is given by


185) A voltmeter has resistance of 2000 Ω and it can measure upto 2V. If we want to increase its range by 8V, then required resistance in series will be


186) The direction of magnetic lines of forces close to a straight conductor carrying current will be


187) The magnetic field at the centre of current carrying coil is


188) A microammeter has a resistance of 100 Ω and full scale range of 50μ A. It can be used as a voltmeter of as a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combinations


189) A charge Q is uniformly distributed over the surface of non-conducting disc of radius R. The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity ω. As a result of this rotation a magnetic field of induction B is obtained at the centre of the disc. If we keep both the amount of charge placed on the disc and its angular velocity to be constant and very the radius of the disc then the variation of the magnetic induction at the centre of the disc will be represented by the figure


190) Two wires of same length are shaped into a square and a circle. If they carry same current, ratio of the magnetic moment is


191) Lorentz force can be calculated by using the formula


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


193) A current flows in a conductor from east to west. The direction of the magnetic field at a point above the conductor is


194) A proton and an electron both moving with the same velocity v enter into region in a magnetic field directed perpendicular to the velocity of the particle.They will now move in circular orbits such that


195) Two similar coils are kept perpendicular such that their centres coincide.at the centre, find the ratio of magnetic field due to one coil and the resultant magnetic field by both coils,if the same currentis flown.


196) A current carries small loop behaves like small magnet.If A be its area and M its magnetic moment ,the current in loop will be


197) A moving coil galvanometer has N number of turns in a coil of effective area A, it carries a current I. The magnetic field B is radial. The torque acting on the coil is


198) When a magnetic field is applied in a direction perpendicular to the direction of cathode rays, then their


199) The current is flowing in south direction along a power line.The direct of magnetic field above the power line (neglecting earth's field) is


200) Two thin,long parallel wires,seperated by distance d carry a current of i ampere in the same direction.They will


201) A uniform magnetic field B and a uniform electric field E, act in a common region.An electron is entering this region of space.The correct arrangement for it to escape undeviated is


202) Which of the following statement is true.


203) A wire of length l is bent in the from of a circular coil of some turns. A current i flows through the coil. The coil is placed in a uniform magnetic field B. The maximum torque on the coil can be


204) Field inside a solenoid is


205) Two long parallel wires carry equal current i flowing in the same direction area at a distance 2d apart.The magnetic field B at the point lying on the perpendicular line joining the wires and distance x from the midpoint is


206) A charged particle is moving with velocity v in a magnetic field of induction B. The force on the particle will be maximum when


207) A particle of mass m and charge q is placed at a rest in a uniform electric field E and then released. The kinetic energy attained by the particle after moving a distance y is


208) A small coil of N turns has area A and a current I flows through it. The magnetic dipole moment of this coil will be


209) A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particle will


210) Positively charged particles are projected into a magnetic field. If the direction of the magnetic field is along the direction of motion of the charge particles, the particles get


211) A charged particle moving in a uniform magnetic field penetrates layer of lead and there by loss one-half of its kinetic energy. How does the radius of curvature of its path change?


212) A current I flows along the length of an infinitely long, straight, thin walled pipe. Then


213) The deflection in a moving coil galvanometer is


214) Two infinitely long parallel wires carry equal current in same direction. The magnetic field at a mid point in between the two wires is


215) 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


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


217) An electron enters a magnetic field whose direction is perpendicular to the velocity of the electron. Then


218) A charged particle moving in a magnetic field experiences a resultant force


219) A strong magnetic field is applied on a stationary electron, then


220) A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled, the deflection will


221) A magnetic field can be produced by


222) If a long hollow copper pipe carries a direct current, the magnetic field associated with the current will be


223) Graph of force per unit length between two long parallel currents carrying conductor and the distance between them is


224) The ratio of the magnitude field at the centre of a current carrying coil of the radius a and at a distance ‘a’ from centre of the coil and perpendicular to the axis of coil is


225) Identify the correct statement from the following


226) A one metre long wire is lying at right angles to the magnetic field. A force of 1 kg wt. is acting on it in a magnetic field of 0.98 tesla. The current flowing in it will be


227) 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, the new value of the magnetic field is


228) A proton, a deuteron and an α- particle with the same kinetic energy enter a region of uniform magnetic field moving at right angles to B. What is the ratio of the radii of their circular paths?


229) A thin disc having radius r and charge q distributed uniformly over the disc is rotated n rotations per second about its axis. The magnetic field at the centre of the disc is