An electron is projected into a magnetic field of flux density \( 10\,\mathrm{Wb/m^2} \) with a velocity of \( 3 \times 10^{7}\,\mathrm{m/s} \) at an angle of 30° to the field. The magnetic force on the electron is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 2.4 \times 10^{-11}\,\mathrm{N} \)
The magnetic Lorentz force depends only on the component of the velocity perpendicular to the field.
\( \displaystyle F = e\,v\,B\sin\theta \)
\( e = 1.6\times10^{-19}\,\mathrm{C}, \quad v = 3\times10^{7}\,\mathrm{m\,s^{-1}} \)
\( B = 10\,\mathrm{Wb\,m^{-2}} = 10\,\mathrm{T}, \quad \sin 30^\circ = 0.5 \)
\( \displaystyle F = 1.6\times10^{-19} \times 3\times10^{7} \times 10 \times 0.5 = 2.4\times10^{-11}\,\mathrm{N} \)