Physics · Electrostatic Potential And Capacitance · NEET
The formula V = kQ/r stays the same, but you must put the charge in WITH its sign. For +q you get V = k(+q)/r which is positive. For -q you get V = k(-q)/r which is negative. Distance r is always positive and k is a positive constant, so only Q decides the sign. Nothing else in the formula can flip it.
No. Potential (V) is a scalar. It has only a value and a sign (+ or -), no direction. Electric field (E) is a vector and has a direction. Do not confuse the minus sign of potential (which means 'below zero, like a valley') with a direction. The minus sign of V is just a number sign, not an arrow.
Not directly linked in sign. Around a lone -q, the potential V is negative everywhere, but the field E points radially inward (toward the charge). Around a lone +q, V is positive and E points radially outward. The sign of V tells you it is below the zero level chosen at infinity; the direction of E is a separate fact. Keep V (scalar sign) and E (vector direction) as two different ideas.
We choose infinity as the reference (zero) point because as r becomes very large, kQ/r becomes very small and tends to 0. From that zero baseline, moving toward a +q climbs to positive V (like climbing a hill), and moving toward a -q drops to negative V (like going into a valley). This is why +q gives V > 0 and -q gives V < 0.
No. Potential V at a point depends only on the SOURCE charge Q that creates the field, not on any test charge you bring. V is a property of the point in space. The test charge only matters for potential ENERGY U = qV, where q is the test charge. Do not mix V (source-only) with U (uses the test charge).
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Electric potential is a scalar quantity. It has a magnitude and a sign (+ or -) but no direction. Electric field is the vector; potential is the scalar.
V = (1/4πε₀)(Q/r) = kQ/r, where k = 9 × 10^9 N m^2 C^-2, Q is the source charge (with its own sign), and r is the distance from the charge. This is directly from NCERT.
Yes. Potential is negative around a negative charge, and can be negative anywhere the net effect of negative charges dominates. Negative V simply means the potential is below the zero level chosen at infinity.
No. Potential V at a point depends only on the source charges creating the field. The test charge only appears in potential energy, U = qV.
Infinity is the chosen reference point. As r tends to infinity, kQ/r tends to 0, so V = 0 there. All other potentials are measured relative to this baseline.
