Magnetic field due to a current carrying conduct or at a point is, `B = (KI)/(r)` , where I is the current through the conductor and r is the distance of a point from the conductor. At 40 cm from the conductor for 15 A current, magnetic field is 60 tesla. Keeping the current same, what is the value of magnetic field (in tesla) at a distance of 20 cm ? (K is the constant of proportionality).

Answer

120

Explanation

We have `B = (KI)/(r )" "…..(i)`
For I = 15, A r = 40 cm , B = n60 tesla .
From equation (i) , we have `B prop I, B prop (1)/(r )`
`therefore " "` For I = 15 A , r = 20 cm , `B = 2 xx B`
` = 2 xx 60 = 120 ` tesla