Question

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

• A. $-1.76\times {10}^{8}coulombs/g$
• B. $1.76\times {10}^{9}coulombs/g$
• C. $-1.76\times {10}^{10}coulombs/g$
• D. $1.76\times {10}^{10}coulombs/g$

Answer 1

Answer: (A)

$-1.76\times {10}^{8}coulombs/g$

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

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

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

Thus answer is option A.