Question

A helium nucleus makes a full rotation in a circle of radius $0.8m$ in $2sec$. The value of the magnetic field induction $B$ in tesla at the centre of circle will be

• A. $2\times {10}^{-19}{\mu }_0$
• B. ${10}^{-19}/{\mu }_0$
• C. ${10}^{-19}{\mu }_0$
• D. $2\times {10}^{-20}/{\mu }_0$

Answer 1

Answer: (C)

${10}^{-19}{\mu }_0$

$B=\frac{{\mu }_0}{4\pi }\frac{2\pi i}{r}$

where $i=\frac{2e}{t}=\frac{2\times 1.6\times {10}^{-19}}{2}=1.6\times {10}^{-19}A$

$\therefore B=\frac{{\mu }_{0}i}{2r}=\frac{{\mu }_0\times 1.6\times {10}^{-19}}{2\times 0.8}={\mu }_0\times {10}^{-19}T$