Q.1
A current i amp flows along an infinitely long straight conductor. If r metre is the perpendicular distance of a point from the lower end of the conductor, then the magnetic induction b is given by [ MPPMT 1994]
  • a)
    ch-16_qn-143choice_img_no1.png
  • b)
    ch-16_qn-143choice_img_no2.png
  • c)
    ch-16_qn-143choice_img_no3.png
  • d)
    ch-16_qn-143choice_img_no4.png
Q.2
The velocity of helium nucleus traveling in the a current path in a magnetic field is v. The velocity of the proton moving along the same path in the same magnetic field field is [ CPMT 1993]
  • a) 4v
  • b) 2v
  • c) v
  • d) v/2
Q.3
In the hydrogen atom, the electron revolves in circular orbit of radius 0.53×10-10 metre and makes 6.6×1015 r.p.s. Then the magnetic dipole moment is approximately [ MPPMT 1999]
  • a)10-29 amp×metre2
  • b) 10-27 amp×metre2
  • c)10-23 amp×metre2
  • d)10-19 amp×metre2
Q.4
Which of the following graph shows the variation of magnetic induction B with distance r from a long wire carrying current : [ MPPMT 1999]
  • a)
    ch-16_qn-146choice_img_no1.png
  • b)
    ch-16_qn-146choice_img_no2.png
  • c)
    ch-16_qn-146choice_img_no3.png
  • d)
    ch-16_qn-146choice_img_no4.png
Q.5
A deuteron of kinetic energy 50 KeV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to magnetic field B. The kinetic energy of the proton that describe a circular orbit of radius 0.5 metre in the same plane with the same B is [ CBSE 1991]
  • a) 25KeV
  • b) 50KeV
  • c)200KeV
  • d)100KeV
Q.6
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 [ CBSE 1991]
  • a) 2.0 cm
  • b) 0.5 cm
  • c) 4.0 cm
  • d) 1.0cm
Q.7
A current loop is placed in a uniform magnetic field. The loop will experience [ CBSE 1993]
  • a)zero linear force but may experience a torque
  • b) a linear force and may experience a torque also
  • c)A linear force only
  • d)zero linear force but will necessarily experience torque
Q.8
A particle of charge q and mass m moving with velocity v along the x-axis enters the region x > 0 with uniform magnetic field B along the k direction. The particle will penetrate in this region in the x-direction up to a distance d equal to [ MPPMT 1997]
  • a) zero
  • b) mv/qB
  • c)2mv/qB
  • d)infinity
Q.9
A current of 1 amp is passed through a straight wire of length 2.0 metres. The magnetic field at a point in air at distance of 3 metres from either end of wire and lying on the axis of wire will be [ MPPMT 1995]
  • a) µo / 2π
  • b) µo / 4π
  • c)µo / 8π
  • d)zero
Q.10
A wire of fixed length L can be formed into many circular loops of varying radii r depending on the number of turns n. The loop so formed is carrying a current and is so placed normally in a uniform magnetic field B. In order that the torque on the circular loop formed be maximum, the number of turns n must be equal
  • a) 1
  • b) 4
  • c) 8
  • d) ∞
Q.11
A proton and an alpha particle enter in a uniform magnetic field with same velocity. The period of rotation of the alpha particle will be [ mPPMT 1990]
  • a)four times that of proton
  • b) two times that of proton
  • c)three times that of proton
  • d)same as that of the proton
Q.12
An electron of charge e is going around in an orbit of radius R metres in hydrogen atom with velocity v m/s. The magnetic flux density associated with it at its centre is [ CBSE 1993]
  • a)
    ch-16_qn-154choice_img_no1.png
  • b)
    ch-16_qn-154choice_img_no2.png
  • c)
    ch-16_qn-154choice_img_no3.png
  • d)
    ch-16_qn-154choice_img_no4.png
Q.13
H+, He++ and O++ all having same kinetic energy pass through a region in which there is a uniform magnetic filed perpendicular to their velocity. The masses of H+,He++ and O++ are 1 amu. 4 amu and 16 amu respectively. Then [ IIT 1994]
  • a) H+ will be deflected most
  • b) O++ will be deflected most
  • c)He + and O++ will deflect equally
  • d)All will be deflected equally
Q.14
Weber ampere per meter is equal to [ MPPMT 1990]
  • a) joule
  • b) newton
  • c) henry
  • d) watt
Q.15
An electron of mass 9×10-31 kg, charge 1.6 ×10-19 C moving with velocity 106 m/s enters a region of magnetic field of strength 5×10-5T perpendicular to the field. Find the radius of the circle described by it
  • a) 9.0 cm
  • b) 11.25 cm
  • c) 13.5 cm
  • d) 15.75 cm
Q.16
A proton of mass 1.67×10-27 kg and charge 1.6×10-19 C is projected with a speed of 2×106 m/s at an angle of 60° to the x-axis. If a uniform magnetic field of 0.104 tesla is applied along the Y-axis, the path of the proton is [ IIT 1995]
  • a)a circle of radius=0.2 m and time period=π×10-7 s
  • b) a circle of radius=0.1 m and time period=2π×10-7 s
  • c)a helix of radius=0.1 m and time period=2π×10-7 s
  • d)a helix of radius=0.2 m and time period=4π×10-7 s
Q.17
A current is flowing in a circular loop of radius R and the magnetic field at its centre is Bo. At what distance from the centre on the axis of the coil, the magnetic field will be Bo / 8? [ MPPMT 1997]
  • a) R√7
  • b) R√3
  • c)2R
  • d)8R
Q.18
Three long, straight and parallel wires carrying currents are arranged as shown in figure. the wire C which carries a current of 5.0 amp is so placed that it experiences no force. the distance of wire C from D is then [ AMU 1995]
ch-16_que_no-159_img_no1.png
  • a) 9 cm
  • b) 7 cm
  • c)5 cm
  • d) 3 cm
Q.19
A conductor in the form of right angle ABC, with AB=3 cm and BC=4 cm, carries a current of 10A. There is uniform magnetic field of 5T, perpendicular to the plane of the conductor. The force on the conductor AC will be [ MPPMT 1997]
ch-16_que_no-160_img_no1.png
  • a) 1.5 N
  • b) 2.0 N
  • c) 2.5 N
  • d) 3.5 N
Q.20
Along vertical wire in which current is flowing produces a neutral point with the earth's magnetic field at distance of 5 cm's from the wire. If the horizontal component of the earth's magnetic induction is 0.18 gauss then current in the wire is
  • a) 0.45 ampere
  • b) 4.5 ampere
  • c)0.9 ampere
  • d)0.036 ampere
Q.21
A very long solenoid has 800 turns per metre length of solenoid. A current of 1.6 ampere flows through it. Then the magnetic induction at the middle point of the solenoid on its axis, is approximately
  • a) 16 × 10-4 tesla
  • b) 8 × 10-4 tesla
  • c)32 × 10-4 tesla
  • d)4 × 10-4 tesla
Q.22
P is a point at a distance a from a long, thin straight wire carrying current i as shown in figure. The magnetic field at P is
ch-16_que_no-164_img_no1.png
  • a) µoi / 2πa
  • b) µoi / 4πa
  • c) µoi / 2a
  • d) µoi / 4a
Q.23
A long thick metallic cylinder of radius R has a current of i ampere uniformly distributed over its circular cross-section. then, magnetic induction B away from the axis at a distance r from the axis varies as shown in figures given in options
  • a)
    ch-16_qn-165choice_img_no1.png
  • b)
    ch-16_qn-165choice_img_no2.png
  • c)
    ch-16_qn-165choice_img_no3.png
  • d)
    ch-16_qn-165choice_img_no4.png
Q.24
A cable carries a current of 1A vertically upward. The magnetic field produced by it at a point 10 cm north will be
  • a) 2 × 10-6 Tesla west
  • b) 2 × 10-6 Tesla east
  • c)2 × 10-8 Tesla west
  • d)2 × 10-8 Tesla vertically upward
Q.25
Magnetic field at the centre of the cube of edge of length a is
ch-16_que_no-167_img_no1.png
  • a)zero
  • b) 8µo i / a √2
  • c)(8µo i√2) / a
  • d)6µo i / a √2
Q.26
A straight conductor of length 0.3 metre is placed in uniform magnetic field of induction 8 × 10-4 tesla, normal to the lines of the force. A current of 2.5 ampere flows through it. The mechanical force acting on the conductor, is
  • a) 6 Newton
  • b) 6 × 10-4 newton
  • c) 6 × 10-2 newton
  • d) 6 × 10-3 newton
Q.27
A circular wire is carrying a current in anticlockwise direction as shown in figure . A long infinite wire CD is placed above the plane of page and carries a current as shown. The force acting on wire CD is
ch-16_que_no-169_img_no1.png
  • a)perpendicular to plane if page and directed towards reader
  • b) perpendicular to plane of page and directed away from reader
  • c)perpendicular to wire CD, in the plane of page and directed towards left of wire
  • d)perpendicular to wire CD in the plane of page and directed to the right of wire CD
Q.28
A long wire carries a steady current. First it is bent into a circular coil of one turn when magnetic induction at the centre is B. Then the same wire is bent to form a circular coil of smaller radius but n turn when the magnetic induction at the centre is B', then
  • a) B'=B
  • b) B'=n B
  • c)B'=n2B
  • d)B=n2B'
Q.29
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
  • a) points upwards
  • b) points vertically downwards
  • c)is zero
  • d)is directly proportional to A2
Q.30
Two concentric circular coils 1 and 2 have radii 20cm and 10cm respectively lie in the same plane. the current in coil 1 is 0.5A in anticlockwise direction. The current in coil 2, so that net field at the common centre is zero, is
  • a) 0.5 A in anticlockwise direction
  • b) 0.25 A in anticlockwise direction
  • c) 0.25 A in clockwise direction
  • d) 0.125 A in clockwise direction
0 h : 0 m : 1 s