Electrostatics Question 223

Question: An infinite number of charges, each of charge 1 mC, are placed on the x-axis with co-ordinates x = 1, 2, 4, 8, ….¥. If a charge of 1 C is kept at the origin, then what is the net force acting on 1 C charge [DCE 2004]

Options:

A) 9000 N

B) 12000 N

C) 24000 N

D) 36000 N

Show Answer

Answer:

Correct Answer: B

Solution:

The schematic diagram of distribution of charges on x-axis.

Total force acting on 1 C charge is given by

F=14πε0[1×1×106(1)2+1×1×106(2)2.

.+1×1×106(4)2+1×1×106(8)2+.]

=1064πε0(11+14+116+164+)=9×109×106(1114)

=9×109×106×43=9×103×43 = 12000 N



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