Ques 9 plz

If a current i is in a circular path of radius R,

 

magnetic field B at centre is given by,  B = μ_o i / ( 2 R )  .............(1)

 

Current i due to electron moving in a circle of radius R with speed v , 

 

i = charge /time = ( e v ) / ( 2 π R ) ................(2)

 

Using eqn.(1) and (2), we get magnetic field as, B = ( μ_o e v ) / ( 4π R² ) 

 

B = ( 4π × 10^-7 × 1.602 × 10^-19 × 7 × 10⁶ ) / ( 4π × 25 × 10^-18 ) = 4.49 × 10^-3 T