# Homework Help: Can the electric potential be negative ?

1. Jun 8, 2014

### Ana Mido

I have just solved a problem about electric potential and it is:
" A positive point charge of 1.0 nC is located at position x=0.00 . A second point charge q=-1.0 nC is located at x=0.10 m.
(a) What is the value of the electric potential on the x-axis at x=0.3 m ?
(b) What is the value of the electric potential on the at x=-0.050 m ? "

I have solved (a) and its answer is "-15". And I know that electric potential is a scalar quantity.

Explain that.

2. Jun 8, 2014

### hilbert2

Electric potential can be negative if you go close enough to a negative charge. One important point, however: the potential does not have an absolutely defined value, you have to arbitrarily give it a value at a certain point. The usual choice in point charge problems is to decide that the potential is zero when you go infinitely far from all charges.

3. Jun 8, 2014

### pasmith

Scalar quantities can be negative. What scalar quantities cannot do is depend on the direction of coordinate axes.

4. Jun 8, 2014

### Ana Mido

OK, is the answer true or is there any ambiguity in the problem ???

5. Jun 8, 2014

### rcgldr

Electric potential is a signed value, with the convention of being postive for a field generated by a positive charge, and negative for a field generated by a negative charge. For a field generated by multiple charged objects, the sign of the potential would depend on location and the charge on the objects that generate the field.