question_answer

Two point charges \[Q\] and ? 3Q are placed at some distance apart. If the electric field at the location of \[Q\] is \[E\] then at the locality of \[-3Q\], it is                                                            [BIT 1987]

A)                    \[-E\]

B)                                      \[E/3\]

C)                    \[-3E\]

D)                                      \[-E/3\]

Correct Answer: B

Solution :

             The field produced by charge ? 3Q at A, this is E as mentioned in the Example. \[\therefore \]\[E=\frac{3Q}{{{x}^{2}}}\] (along AB directed towards negative charge) Now field at location of ? 3Q i.e. field at B due to charge Q will be \[E'=\frac{Q}{{{x}^{2}}}=\frac{E}{3}\] (along AB directed away from positive charge)