Question

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

• A. $- E$
• B. E/3
• C. $- 3E$
• D. – E/3

Answer 1

Answer: (B)

E/3

Answer 2

Let the charge Q and – 3Q be placed respectively at A and B at a distance x Now we will determine the magnitude and direction to 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)