Electrostatics Question 253

Question: An infinite number of electric charges each equal to 5 nano-coulomb (magnitude) are placed along X-axis at x=1 cm, x=2 cm, x=4 cm x=8 cm … and so on. In the setup if the consecutive charges have opposite sign, then the electric field in Newton/Coulomb at x=0 is (14πε0=9×109Nm2/c2) [EAMCET 2003]

Options:

A) Ze22πε0mv2

B) Ze4πε0mv2

C) Ze28πε0mv2

D) Ze8πε0mv2

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Answer:

Correct Answer: A

Solution:

Suppose distance of closest approach is r, and according to energy conservation applied for elementary charge.

Energy at the time of projection = Energy at the distance of closest approach

therefore 12mv2=14πε0.(Ze).err=Ze22πε0mv2



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