How do you appreciate the relation between magnetic that changed the life style of mankind?

Here magnetic induction of the field is always

  1. Directly proportional to the current B $\propto$ i
  2. Inversely proportional to the radius of the coil B $\propto$ 1/r
  3. Directly proportional to the number of turns B$\propto$ N=====>B $\propto$ iN / r So if current is more, induction is also more.