A proton moving vertically downward enters a magnetic field

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 Multiple Choice QuestionsMultiple Choice Questions

211.

A galvanometer can be changed into an ammeter by using

  • low resistance shunt in series

  • low resistance shunt in parallel

  • high resistance shunt in series

  • high resistance shunt in parallel


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212.

A proton moving vertically downward enters a magnetic field pointing towards north. In which direction proton will deflect?

  • East

  • West

  • North

  • South


A.

East

Proton will represent the direction of current. So, the direction of current is vertically downward.

According to Fleming's left hand rule, if middle finger represents the direction of current and fore-finger represents the direction of magnetic field then thumb will represent the direction of Lorentz force acting on the proton which deflects the proton in east direction.


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213.

A coil of n number of turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current of strength I is passed through the coil, the magnetic field at its centre is

  • μo nIb - a loge ab

  • μo n I2 b - a

  • 2 μo nIb

  • μo nI2 b - a loge ba


214.

A galvanometer acting as a voltmeter should have

  • low resistance in series with its coil

  • low resistance in parallel with its coil

  • high resistance in series with its coil

  • high resistance in parallel with its coil


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215.

Magnetic field at point O will be

 

  • μo I2R interior

  • μoI2R exterior

  • μo I2R1 - lπ interior

  • μoI2R 1 + Iπ exterior


216.

If the electric flux entering and leaving an enclosed surface respectively are ϕ1 and ϕ2 , the electric charge inside the surface will be

  • ϕ2 - ϕ1εo

  • ϕ2 + ϕ1εo

  • ϕ1 - ϕ2ε0

  • ε0 ϕ1 +  ϕ2 


217.

Two long straight wires, each carrying an electric current of 5 A, are kept parallel to each other at a separation of 2.5 cm. Find the magnitude of the magnetic force experiment by 10 cm of a wire.

  • 4.0 × 10-4 N

  • 3.5 × 10-6 N

  • 2.0 × 10-5 N

  • 2.0 × 10-9 N


218.

The parts of two concentric circular arcs joined by two radial lines and carries current i. The arcs subtend an angle 0 at the centre of the circle. The magnetic field at the centre O, is

  • μ0 i b - a  θ4π ab

  • μ0i b - aπ - θ 

  • μ0i  b - a θπab

  • μ0i a - b2πab


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219.

A square loop is made by a uniform conductor wire as shown in figure

     

The net magnetic field at the centre of the loop if side length of the square is a

  • μ0 i2 a

  • zero

  • μ0 i2a2

  • None of these


220.

A thin bar magnet of length 2 L is bent at the mid-point so that the angle between them is 60°. The new length of the magnet is

  • L/2√3

  • √3 L/2

  • L

  • 2 L/3


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