Minimum number of unequal vectors which can give zero resultant are (a) two
(b) three
(c) four
(d) more than four

minimum number of unequal vectors which can give zero resultant are.

Ans - Three

Explanation:

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the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.