Q 1 :    

Given below are two statements:

 

Statement (I): When currents vary with time, Newton's third law is valid only if momentum carried by the electromagnetic field is taken into account.

 

Statement (II): Ampere's circuital law does not depend on Biot-Savart's law.

 

In the light of the above statements, choose the correct answer from the options given below:              [2024]

  • Both Statement I and Statement II are false.

     

  • Statement I is true but Statement II is false.

     

  • Statement I is false but Statement II is true.

     

  • Both Statement I and Statement II are true.

     

(B)    Statement Ist is true

         Statement IInd is false as Ampere's law depends on Biot Savart's law.

 



Q 2 :    

A solenoid of length 0.5 m has a radius of 1 cm and is made up of 'm' number of turns. It carries a current of 5 A. If the magnitude of the magnetic field inside the solenoid is 6.28×10-3T then the value of m is _______ .               [2024]



(500)    μ0ni=B

           n = number of turns per unit length

           μ0(ml)i=B

          m=B.lμ0i=6.28×10-3×0.512.56×10-7×5=500



Q 3 :    

In a co-axial straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero         [2024]

  • outside the cable

     

  • in between the two conductors

     

  • inside the inner conductor

     

  • inside the outer conductor

     

(1)

B·d=μ0ienc=0    B=0 outside the cable

 



Q 4 :    

A long straight wire of radius a carries a steady current I. The current is uniformly distributed across its cross-section. The ratio of the magnetic field at a2 and 2a from axis of the wire is ______.                 [2024]

  • 1 : 1

     

  • 3 : 4

     

  • 1 : 4

     

  • 4 : 1

     

(1)

Magnetic field inside wire,

Binside=μ0Jr2=μ0Ir2A=μ0Ir2πa2

ra2Binside=μ0I4πa

Magnetic field outside, B2=μ0i2πr

B2=μ0i2π(2a)=μ0i4πa

Binside=μ0I4πa

So  B1=B21:1