A charged dust particle of radius 5 × 10 ^ - 7 m is located in a horizontal electric field having an intensity of 6.28 × 10 ^ 5 Vm^ - 1 . The surrounding medium in air with coefficient of viscosity η = 1.6 × 10 ^ - 15

Correct answer: B. 15 neE = 6πηrv or n = (6πηrv)/(eE) = 6 × 3.14 × 1.6 × 10 ^ - 5 × 5 × 10 ^ - 7 × 0.01 1.6 × 10 ^ - 19 × 6.28 × 10 ^ 5 = 15

NTA Abhyas 2020

NTA Abhyas 2020 · Physics · Electromagnetic Waves

A charged dust particle of radius 5 × 10 ^ - 7 m is located in a...

A charged dust particle of radius

5 \times {10}^{- 7}m

is located in a horizontal electric field having an intensity of

6.28 \times {10}^{5}Vm^{- 1}

. The surrounding medium in air with coefficient of viscosity

η = 1.6 \times {10}^{- 15}Nsm^{- 2}.

If this particle moves with a uniform horizontal speed of

0. 01ms^{- 1},

the number of electrons on it will be

B. $15$

neE = 6\piηrv

n = \dfrac{6\piηrv}{eE}

= \dfrac{6 \times 3.14 \times 1.6 \times {10}^{- 5} \times 5 \times {10}^{- 7} \times 0.01}{1.6 \times {10}^{- 19} \times 6.28 \times {10}^{5}} = 15