Question

If current in the coil decreases, then strength of the magnetic field

• A. decreases
• B. increases
• C. sometimes decreases and sometimes increases
• D. remains unchanged

Answer 1

The correct option is A decreases

Magnetic field due to a current carrying coil is given by, $B=\left({\mu }_{0}NI{r}^2\right)/\sqrt{(z^2+r^2{)}^3}$
As we can see from the relation magnetic field is directly proportional to the current value ,
so decreasing the current value will decrease the magnetic field also.