NEET Physics - New - Magnetic Effects of Current and Magnetism

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Question - 1

A long solenoid of diameter 0.1 m has 2 x 104 turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to OA from 4 A in 0.05s.If the resistance of the coil is 10π2Ω, the total charge flowing through the coil during this time is:

  • A 16 μC
  • B 32 μC
  • C 16 πμC
  • D 32 πμC

Question - 2

A 250 turns rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μA and subjected to a magnetic field of strength 0.85T. Work done for rotating the coil by 1800 against the torque is :

  • A 4.55 μJ
  • B 2.3 μJ
  • C 1.15 μJ
  • D 9.1 μJ

Question - 3

A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be:

  • A nB
  • B n2B
  • C 2nB
  • D 2n2B

Question - 4

An electron is moving in a circular path under the influence of a transverse magnetic field of 3.57 x 10-2 T. If the value of elm is 1.76 x 1011 C/kg, frequency of revolution of the electron is

  • A 1 GHz
  • B 100 MHz
  • C 6.28 MHz
  • D 6.28 MHz

Question - 5

A, B and C are voltmeters of resistance R, 1.5 R and 3R respectively as shown in the fig. When some potential difference is applied between X and Y, the voltmeter reading are VA, VB and VC respectively.

  • A VA = VB = VC
  • B VA ≠ VB = VC
  • C VA = VB ≠ VC
  • D VA ≠ VB ≠ VC

Question - 6

A conducting square frame of side a and a long straight wire carrying current I and located in the same plane as shown in the figure. The frame moves to the right with a constant velocity v. The emf induced in the frame will be proportional to

  • A 1/x2
  • B 1/(2x-a)2
  • C 1/(2x+a)2
  • D 1/(2x-a)(2x+a)

Question - 7

Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that 'O' is their common point for the two. The wires carry I1 and I2 currents, respectively. Point 'P' is lying at distance "d' from 'O' along a direction perpendicular to the plane containing the wires. The magnetic field at the point 'P' will be :

  • A (μ0/2πd) x (I1/I2)
  • B (μ0/2πd) (I1/I2)
  • C (μ0/2πd) x (I21-I22)
  • D (μ0/2πd) x (I21+I22)1/2

Question - 8

Two free parallel wires carrying currents in opposite directions

  • A Attract each other
  • B Repel each other
  • C Neither attract nor repel
  • D Get rotated to be perpendicular to each other

Question - 9

Two thin long parallel wires separated by a distance b are carrying a current i amp each. The magnitude of the force per unit length exerted by one wire on the other is

  • A μ0i2/b2
  • B μ0i2/2πb
  • C μ0i/2πb
  • D μ0i/2πb2

Question - 10

Through two parallel wires A and B, 10 and 2 ampere of currents are passed respectively in opposite directions. If the wire A is infinitely long and the length of the wire B is 2 m, the force on the conductor B, which is situated at 10 cm distance from A will be :

  • A 8 x 10-5 N
  • B 4 x 10-7 N
  • C 4 x 10-5 N
  • D 4π x 10-7 N