Q.1
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.2
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.3
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.4
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.5
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.6
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.7
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.8
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.9
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.10
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.11
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.12
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
Q.13
When a straight conductor is carrying an electric current
  • a)there are circular magnetic line of force around it
  • b) there are no magnetic line of force near it
  • c)there are magnetic lines of force parallel to conductor along the direction of current
  • d)there are magnetic lines of force parallel to conductor opposite to the direction of current
Q.14
The change in the kinetic energy of a charged particle moving in a uniform magnetic field will be zero when its velocity is
  • a) parallel to the magnetic field
  • b) perpendicular to the magnetic field
  • c)at any angle with the magnetic field
  • d)in all of the above cases
Q.15
A conducting rod PQ of length l carrying a current I is suspended from a support as shown in figure. A uniform magnetic field B perpendicular to PQ and directed away from the reader is applied. If the mass of the bar is M, the tension in each string is
ch-16_que_no-176_img_no1.png
  • a) Mg/2
  • b) (Mg+IB/)/2
  • c) (Mg -IBl)/2
  • d) Mg - (IBl)/2
Q.16
A beam of electrons is accelerated through a potential difference V. It is then passed normally through a uniform magnetic field where it moves in a circle of radius r. It would have moved in a circle of radius 2r if it were initially accelerated through a potential difference .....
  • a) √2 V
  • b) 2 V
  • c)2√2 V
  • d)4 V
Q.17
The strength of the magnetic field due to a long straight conductor is
  • a) same everywhere around the conductor
  • b) inversely proportional to the distance from the conductor
  • c) inversely proportional to the square of the distance from the conductor
  • d) inversely proportional of cube of the distance from the conductor
Q.18
A square frame of side L carries a current i and the field at the centre of the frame is B. The square frame is recast into circular coil of radius R. When same current i is passed through the circular coil, the magnetic field at its centre is B'. The ratio B/B' is
  • a)8/π2
  • b) 8√2 / π2
  • c)16/π2
  • d)(8/√2)π2
Q.19
The magnetic induction at point P which is distance 4cm from along current carrying wire is 10-3 tesla. The field of induction at a distance 12cm from the same current would be
  • a) 3.33 ×10⁻⁴ tesla
  • b) 1.11 × 10⁻⁴ tesla
  • c)3 × 10⁻³ tesla
  • d)9 × 10⁻³ tesla
Q.20
The magnetic field at the centre of a square loop of side L carrying current I is
  • a)
    ch-16_qn-180choice_img_no1.png
  • b)
    ch-16_qn-180choice_img_no2.png
  • c)
    ch-16_qn-180choice_img_no3.png
  • d) None of the above
Q.21
A long 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 option
  • a)
    ch-16_qn-183choice_img_no1.png
  • b)
    ch-16_qn-183choice_img_no2.png
  • c)
    ch-16_qn-183choice_img_no3.png
  • d)
    ch-16_qn-183choice_img_no4.png
Q.22
A rectangular coil of cross-section A is placed in uniform magnetic field B as shown in figure. The magnetic flux through the coil is
ch-16_que_no-185_img_no1.png
  • a)B.A
  • b) B.Asinα
  • c)B.Acosα
  • d)none of these
Q.23
Two wires A and B carry current as shown in figure the magnetic interactions
ch-16_que_no-186_img_no1.png
  • a) Push I2 away from I1
  • b) Pull I2 closer to I1
  • c)Turn I2 clockwise
  • d)Turn I2 counter clockwise
Q.24
A solenoid has 1000 turns wound on a length of 20cm. It carries a current of 5A. The magnetic field at one end of the solenoid is
  • a)0.031 T
  • b) 0.0155 T
  • c)0.00775 T
  • d)0.062 T
Q.25
A wire bent in the form of a regular polygon of n sides, is inscribed in a circle of radius 'a' metre . If i ampere is the current flowing through wire, then the magnetic flux density at the centre of the circle is
  • a)
    ch-16_qn-189choice_img_no1.png
  • b)
    ch-16_qn-189choice_img_no2.png
  • c)
    ch-16_qn-189choice_img_no3.png
  • d)
    ch-16_qn-189choice_img_no4.png
Q.26
Two identical coils carry equal currents have a common centre and their planes are at right angles to each other. What is the ratio of magnitudes of the resultant magnetic field and the field due to one coil alone at the centre
  • a) 2 : 1
  • b) 1 : 1
  • c) 1 : √2
  • d)√2 : 1
Q.27
A wire bent in the form of sector of radius r subtending an angle θo at centre, as shown in figure is carrying a current i. the magnetic field at O is
ch-16_que_no-191_img_no1.png
  • a)
    ch-16_qn-191choice_img_no1.png
  • b)
    ch-16_qn-191choice_img_no2.png
  • c)
    ch-16_qn-191choice_img_no3.png
  • d)zero
Q.28
A uniform wire of mass 10-3 kg/cm is held at rest in horizontal position without any support by placing it in a uniform, perpendicular magnetic field. The wire is carrying a current of 10A. The magnetic field is
  • a) 0.1 T
  • b) 1.0 T
  • c) 10-2 T
  • d) 10-3 T
Q.29
Two thick wire and two thin wires all of the same material and same length form a square in three different ways P, Q, and R as shown in figure. With the current connections as shown, the magnetic field at the centre of the square is zero in case of :
ch-16_que_no-193_img_no1.png
  • a) P only
  • b) P and Q only
  • c)Q and R only
  • d)P and R only
Q.30
Current I flows through a long conducting wire bent at right angles as shown in figure. The magnetic field at a point P on the right bisector or ∠ XOY at distance r from O is
ch-16_que_no-194_img_no1.png
  • a)
    ch-16_qn-194choice_img_no1.png
  • b)
    ch-16_qn-194choice_img_no2.png
  • c)
    ch-16_qn-194choice_img_no3.png
  • d)
    ch-16_qn-194choice_img_no4.png
0 h : 0 m : 1 s