Question

The ratio of charge to mass of an electron in coulombs per gram was determined by J.J. Thomson. He determined this ratio by measuring the deflection of cathode rays in electric and magnetic fields. What value did he find for this ratio?

• A. $-1.76\times {10}^{8}C/g$
• B. $1.76\times {10}^{-8}C/g$
• C. $-1.76\times {10}^{10}C/g$
• D. $-1.76\times {10}^{-10}C/g$

Answer 1

The correct option is A $-1.76\times {10}^{8}C/g$

Charge of an electron is

$=-1.6\times {10}^{-19}C$

Mass of electron is

$9.1\times {10}^{-31}kg=9.1\times {10}^{-28}g$

Thus, Charge/mass ratio is

$\frac{-1.6\times {10}^{-19}}{9.1\times {10}^{-28}}=-1.76\times {10}^{8}coulombs/g$

Thus the correct option is A.