Question

an electron is moving in a circle of radius 4r in a uniform magnetic field B/2.if the field is reduced to B/4.then what would be the new radius of the circle?​

Answer 1

SOLUTION-;

• r=  
• Bq
• mu
• ​  
•  
• ⇒r  
• 1
• ​  
• B  
• 1
• ​  
• =r  
• 2
• ​  
• B  
• 2
• ​  
•  
• ⇒r⋅B=r  
• 1
• ×  
• 2
• B
• ​  
•  
• ⇒r  
• 1
• =2r.
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Answer 2

Answer:

The new radius of the circle is 8r.

Explanation:

• The space or region around the current carrying wire/moving electric charge or around the magnetic material in which force of magnetism can be experienced by other magnetic material is called as magnetic field/magnetic induction by that material/current.
• It is denoted by B.
• The radius of the path followed by a charge particle in magnetic field is given by:     R=qv/mB ------(1)

where q=charge, v=velocity ,m= mass, B= magnetic field

According to the given question

​ Case 1: R₁=4r and B₁=B/2

       Case 2:R₂=? and B₂=B/4

From equation 1, we have

                  R ∝ 1/B

                ∴   R₁/R₂ = (1/B₁)÷(1/B₂)

                       4r/R₂ = (2/B)÷(4/B)

                       4r/R₂ = (2/B)×(B/4)

                        R₂=4r×2

                        R₂=8r

  #SPJ2