Question

A hypothetical sub-atomic particle has a mass one-third of an electron and a charge double than that of a proton. Calculate the charge to mass ratio of the particle.

• A. $1.05\times {10}^{-12}{\text{C kg}}^{-1}$
• B. $1.05\times {10}^{12}{\text{C kg}}^{-1}$
• C. $8.36\times {10}^{21}{\text{C kg}}^{-1}$
• D. $1.05\times {10}^{-21}{\text{C kg}}^{-1}$

Answer 1

The correct option is B $1.05\times {10}^{12}{\text{C kg}}^{-1}$

Mass of the particle $=\frac{\text{mass of electron}\left(m_e\right)}{3}=\frac{\left(m_e\right)}{3}$

Charge of the particle $=+2e$
$\frac{e}{m}=\frac{2e}{\frac{m_e}{3}}=\frac{6e}{m}$
$=6\times 1.758820\times {10}^{11}{\text{C kg}}^{-1}=1.05\times {10}^{12}{\text{C kg}}^{-1}$