Number of turns on the circular coil, \(\mathrm{n}=20\)
Radius of the coil, \(\mathrm{r}=10 \mathrm{~cm}=0.1 \mathrm{~m}\)
Magnetic field strength, \(\mathrm{B}=0.10 \mathrm{~T}\)
Current in the coil, \(\mathrm{I}=5.0 \mathrm{~A}\)
(a) The total torque on the coil is zero because the field is uniform.
(b) The total force on the coil is zero because the field is uniform.
(c) Cross-sectional area of copper coil, \(\mathrm{A}=10^{-5} \mathrm{~m}^{2}\)
Number of free electrons per cubic meter in copper, \(\mathrm{N}=10^{29} / \mathrm{m}^{3}\)
Charge on the electron, e \(=1.6 \times 10^{-19} \mathrm{C}\)
Magnetic force, \(\mathrm{F}=\) Bevd
vd \(=\) Drift velocity of electrons
\(\quad=\frac{l}{\text { NeA }}\)
\(\therefore F=\frac{\text { Bel }}{\text { NeA }}\)
\(\quad=\frac{0.10 \times 5.0}{10^{29} \times 10^{-5}}=5 \times 10^{-25} \mathrm{~N}\)
Hence, the average force on each electron is \(5 \times 10^{-25} \mathrm{~N} .\)
