A proton moves with a speed of 5.0 x 106 m/s along the x-axis. It

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

41.

The resistance of the tungsten wire in the light bulb, which is 120V/75 W and powered by a 120 V direct current supply, is

  • 0.37 Ω

  • 1.2 Ω

  • 2.66 Ω

  • 192 Ω


42.

The value of the current I1, I2 and I3 flowing through the circuit given below is

      

  • I1 = − 3A, I2 = 2A, I3 = − 1A

  • I1 = 2A, I2 = − 3A, I3 = − 1A

  • I1 = 3A, I2 = − 1A, I3 = − 2A

  • I1 = 1A, I2 = − 3A, I3 = − 2A


43.

A silver wire has temperature coefficient of resistivity 4 x 10-3 / °C and its resistance at 20°C is 10 Ω. Neglecting any change in dimensions due to the change in temperature, its resistance at 40°C is

  • 0.8 Ω

  • 1.8 Ω

  • 9.2 Ω

  • 10.8 Ω


44.

A charge Q placed at the centre of a metallic spherical shell with inner and outer radii R1 and R2 respectively. The normal component of the electric field at any point on the Gaussian surface with radius between R1 and R2 will be

  • Zero

  • Q4πR12

  • Q4πR22

  • Q4π (R1 - R2)2


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45.

A sphere of radius R has a uniform volume charge density ρ. The magnitude of electric field at a distance r from the centre of the sphere, where r > R, is

  • ρ4πε0r2

  • ρR2ε0r2

  • ρR3ε0r2

  • ρR33ε0r2


46.

Five equal point charges with Q = 10 nC are located at x = 2, 4, 5, 1 O and 20 m. If ε0 = [10-9 / 36π] F/m, then the potential at the origin (x = O) is

  • 9.9 V

  • 11.1 V

  • 90 V

  • 99 V


47.

Two infinitely long parallel plates of equal areas 6 cm2 are separated by a distance of 1 cm. While one of the plates has a charge of + 10 nC and the other has − 10 nC. The magnitude of the electric field between the plates, if ε0 = 10-936π F/m is

  • 0.6 π kV/m

  • 6 π kV/m

  • 600 π kV/m

  • 60 π V/m


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48.

A proton moves with a speed of 5.0 x 106 m/s along the x-axis. It enters a region where there is a magnetic field of magnitude 2.0 Tesla directed at an angle of 30° to the
x-axis and lying in the xy-plane. The magnitude of the magnetic force on the proton is

  • 0.8 × 10-13 N

  • 1.6 × 10-13 N

  • 8.0 × 10-13 N

  • 8.01 × 10-13 N


C.

8.0 × 10-13 N

Given, 

The speed of proton v = 5.0 × 106 m/s

Magnetic field, B = 2.0 Tesla

Angle θ = 30°

Charge on proton, q = 1.6 × 10-19 C

When the proton enters in magnitude field, it experiences Lorentz force

          F = q (v × B)F = qvB sin θ   F= 1.6 × 10-19 × 5 × 106 × 2 × sin 30°      = 8.0 × 10-13 N


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49.

A long straight wire of radius R carries a steady current I0, uniformly distributed throughout the cross-section of the wire. The magnetic field at a radial distance r from the centre of the wire, in the region r > R, is

  • μ0I02πr

  • μ0I02πR

  • μ0I0R22πr

  • μ0I0r22πR


50.

If the cyclotron oscillator frequency is 16 MHz, then what should be the operating magnetic field for accelerating the proton of mass 1.67 x 10-27 kg ?

  • 0.334 πT

  • 3.34 πT

  • 33.4 πT

  • 334 πT


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