MCQ
In a Thomson set-up for the determination of $\mathrm{e} / \mathrm{m}$, electrons accelerated by $2.5 \mathrm{kV}$ enter the region of crossed electric and magnetic fields of strengths $3.6 \times 10^4 \mathrm{Vm}^{-1}$ and $1.2 \times 10^{-3} \mathrm{~T}$ respectively and go through undeflected. The measured value of $e / m$ of the electron is equal to
- A$1.0 \times 10^{11} \mathrm{C}-\mathrm{kg}^{-1}$
- B$1.76 \times 10^{11} \mathrm{C}-\mathrm{kg}^{-1}$
- ✓$1.80 \times 10^{11} \mathrm{C}-\mathrm{kg}^{-1}$
- D$1.85 \times 10^{11} \mathrm{C}-\mathrm{kg}^{-1}$