Magnetic and electric field are acting on a proton moving with ve

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 Multiple Choice QuestionsMultiple Choice Questions

291.

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 :

  • I is doubled

  • B is halved

  • r is doubled

  • Both B and I are doubled


292.

Two parallel wires carrying current in the same direction attract each other because of :

  • the potential difference between them

  • mutual inductance between them

  • the electric force between them

  • the magnetic force between them


293.

A galvanometer has a resistance of 400 Ω and deflects full scale for a current of 0.2 mA through it. The shunt resistance required to covert it into 3A ammeter is :

  • 0.027 Ω

  • 0.054 Ω

  • 0.0135 Ω

  • none of these


294.

A coil having N turns carries a current as shown in the figure. The magnetic field intensity at point P is :

  • μ0NiR22(R2 + x2)3/2

  • μ0Ni2R

  • μ0NiR2(R + x)2

  • zero


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295.

An electron moves at a right angle to a magnetic field of 1.5 x 10-2 tesla with a speed of 6 x 107 m/s. If the specific charge of the electron is 1.7 x 1011 coulomb/kg, the radius of the circular path will be

  • 2.9 cm

  • 3.9 cm

  • 2.35 cm

  • 2 cm


296.

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

  • R

  • R2

  • R/2

  •  2R


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297.

Magnetic and electric field are acting on a proton moving with velocity ν. Proton will be undeflected if 

  • E is parallel to v, but perpendicular to B

  • E and B both are parallel to v

  • E and B are perpendicular to each other

  • E, B and v are perpendicular to one another and v=EB


D.

E, B and v are perpendicular to one another and v=EB

Since,proton is undeflected,therefore net force on it is zero

             F= qE + q(v ×B) = 0

               = qE = -q(v×B)

In this condition, E,B and v are perpendicular to one another.


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298.

A current of 0.1 ampere is flowing through a coil of 1000 turns and radius 0.1 metre. The magnetic field at the centre of the coil is

  • 2 × 10−1 T

  • 4.31 × 10−2  T

  • 6.28 × 10−4  T

  • 9.81 × 10−4  T


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299.

In a galvanometer of 5 ohm resistance, a wire of 2 ohm resistance is used as a shunt. If the total current is 1 ampere, the fraction of current that will flow through the shunt is

  • 1.2 A

  • 0.7 A

  • 0.5 A

  • 0.3 A


300.

A solenoid of length 5O cm and a radius of cross-section 1 cm has 1000 turns of wire wound over it. If the current carried is 5 A, the magnetic field on its axis, near the centre of the solenoid is approximately (permeability of free space μ04π × 10-7 T-m/A)

  • 0.63 × 10−2 T

  • 1.26 × 10−2 T

  • 2.51 × 10−2 T

  • 6.3 T


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