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Karnataka Board PUCPUC Science Class 11

Ten Positively-charged Particles Are Kept Fixed on the X-axis at Points X = 10 Cm, 20 Cm, 30 Cm, ...., 100 Cm. the First Particle Has a Charge 1.0 × 10−8 C, the Second 8 × 10−8 C,The Third 27 × 10−8 C - Physics

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Question

Ten positively-charged particles are kept fixed on the x-axis at points x = 10 cm, 20 cm, 30 cm, ...., 100 cm. the first particle has a charge 1.0 × 10−8 C, the second 8 × 10−8 C, the third 27 × 10−8 C and so on. The tenth particle has a charge 1000 × 10−8 C.  Find the magnitude of the electric force acting on a 1 C charge placed at the origin. 

Short Note

Solution

By Coulomb's Law, force (F) on charge q due to one charge,            

\[F = \frac{1}{4\pi \epsilon_0}\frac{q_1 q}{r^2}\]
So, net force due to ten charges, 

\[F =  F_1  +  F_2  +  F_3  +  .  .  .  .  .  +  F_{10} \] 

\[       = 9 \times  {10}^9  \times \left[ \frac{1 . 0}{\left( 0 . 10 \right)^2} + \frac{8}{\left( . 20 \right)^2} + \frac{27}{\left( . 30 \right)^2} + . . . . . . \frac{1000}{\left( 1 . 0 \right)^2} \right] {10}^{- 8} \] 

\[       = \frac{9 \times {10}^9 \times {10}^{- 8}}{{10}^{- 2}}\left[ 1 + 2 + 3 + . . . . . . 10 \right]\] 

\[         = 9 \times  {10}^3  \times 55\] 

\[         = 4 . 95 \times  {10}^5\] N

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Chapter 7: Electric Field and Potential - Exercises [Page 121]

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HC Verma Concepts of Physics Vol. 2 [English] Class 11 and 12
Chapter 7 Electric Field and Potential
Exercises | Q 20 | Page 121

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