A square current carrying loop is suspended in a uniform magneti

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181.

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is bold F with bold rightwards arrow on top, the net force on the remaining three arms of the loops is

  • bold F with bold rightwards arrow on top

  • -bold F with bold rightwards arrow on top

  • negative 3 space bold F with bold rightwards arrow on top
  • negative 3 space bold F with bold rightwards arrow on top


B.

-bold F with bold rightwards arrow on top

When a current carrying loop is placed in a magnetic field, the coil experiences a torque given by  T = NBiA sin θ. Torque is maximum when θ =90, i.e. the plane of the coil is parallel to the field Tmax NBiA



Force  and  acting on the coil are equal in magnitude and opposite in direction. As the forces   and   have the same line action their reultant effect on the coil is zero. 
The two forces  are equal in magnitude and opposite in direction. As the two forces have different lines of action, they constitute a torque .Thus, if the force on one arc of the loop is , the net force on the remaining three arms of the loop is -F.

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182.

A particle having a mass of 10-2 kg carries a charge of 5 x 10-8 C. The particle is given an initial horizontal velocity of 105 ms-1 in the presence of electric field andbold E with bold rightwards arrow on top magnetic field.bold B with rightwards arrow on top To keep the particle moving in a horizontal direction. it is necessary that

1) bold B with rightwards arrow on top should be perpendicular to the direction of velocity and bold E with bold rightwards arrow on top should be along the direction of velocity

2) Both bold B with rightwards arrow on top and bold E with bold rightwards arrow on top should be along the direction of velocity.

3) Both bold B with rightwards arrow on top and bold E with bold rightwards arrow on top are mutually perpendicular and perpendicular  to the direction of  velocity

4) bold B with rightwards arrow on top should be along the direction of velocity and bold E with bold rightwards arrow on top should be perpendicular to the direction of velocity.

  • (1) and (3)

  • (3) and (4)

  • (2) and (3)

  • (2) and (3)

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183.

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 parts at their common centre is

  • fraction numerator straight mu subscript straight o space straight i over denominator 2 square root of 2 straight R end root end fraction
  • fraction numerator straight mu subscript 0 straight i over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight i over denominator 4 straight R end fraction
  • fraction numerator straight mu subscript straight o straight i over denominator 4 straight R end fraction
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184.

A wire of resistance 12 Ωm-1 is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite point, A and B as shown in the figure, is

  • 0.6 π Ω

  •  3 π Ω

  • 6 π Ω

  • 6 π Ω

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185.

A student measures the terminal potential difference (V) of a cell (of emf and internal resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively, equal

  • straight epsilon space and space minus straight r
  • negative straight r space and space straight epsilon
  • straight r space and space minus straight epsilon
  • straight r space and space minus straight epsilon
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186.

The magnetic force acting on a charged particle of charge -2 μC in a magnetic field of 2T acting in y direction, when the particle velocity is left parenthesis 2 straight i with hat on top space plus 3 straight j with hat on top right parenthesis space straight x space 10 to the power of 6 space ms to the power of negative 1 end exponent space is

  • 8N in -z direction

  • 4N in z direction

  • 8 N in y direction

  • 8 N in y direction

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187.

A particle mass m, charge Q and kinetic energy T enter a transverse uniform magnetic field of induction.bold B with rightwards arrow on top After 3 s the kinetic energy of the particle will be

  • 3T

  • 2T

  • T

  • T

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188.

A long solenoid has 500 turns. When a current of 2 A is passed through it, the resulting magnetic flux linked with each turn of the solenoid is 4 x 10-3 Wb. The self -inductance of the solenoid is 

  • 2.5 H

  • 2.0 H

  • 1.0 H

  • 1.0 H

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189.

A galvanometer of resistance 50 Ω is connected to a battery of 3 V along with a resistance of 2950 Ω in series. A full-scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

  • 5050 Ω

  • 5550 Ω

  • 6050 Ω

  • 6050 Ω

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190.

Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them so that the magnetic field at their centres is the same?

  • 3

  • 4

  • 6

  • 6

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