Question

A long soleniod has 200 turns per cm and carries a current i. The magnetic field at its centre is $6.28\times {10}^{-2}Weber/m^2$. Another long solenoid has 100 turns per cm and it carries a current $\frac{i}{3}$ The value of the magnetic field at its centre is

• A. $1.05\times {10}^{-4}Weber/m^2$
• B. $1.05\times {10}^{-2}Weber/m^2$
• C. $1.05\times {10}^{-5}Weber/m^2$
• D. $1.05\times {10}^{-3}Weber/m^2$

Answer 1

The correct option is B $1.05\times {10}^{-2}Weber/m^2$

$B_2=\frac{B_1{n}_2{i}_2}{n_1{i}_1}=\frac{(6.28\times {10}^{-2})(100\times \frac{i}{3})}{200\left(i\right)}=1.05\times {10}^{-2}W/m^2$