Question

Three points A, B, and C of unknown charges are at the corners of an equilateral triangle.

Answer 1

Answer: option d. 

$Q_A= \frac{1}{2} Q_B=- \frac{1}{3} Q_C$

Explanation:


1) The direction of the field lines inform about the sign of the charges.

The field lines extend from the positive charges to the negative charges, so you can conclude that the charge C is positve and both charge A and charge B are negative:


Charge C: positive

Charge A: negative

Charge B: netative


2) The density of the lines (number of lines in a region) inform about the magnitude of the electric field.

Since the charges are at the same distance, the magnitude of the electric field informs directly about the magnitude of the force and that about the magnitude of the charges.

Since, there are the double of lines between C and B than between C and A, the magnitude of charge B is the double than the magnitud of charge A.

From the five options given (a throug e) the only that is consistent with that charges A and B have the same sign, that charge C has different sign, and that charge B is the double of charge A is:

$Q_A= \frac{1}{2} Q_B=- \frac{1}{3} Q_C$