{"id":565,"date":"2026-07-15T02:45:32","date_gmt":"2026-07-15T02:45:32","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=565"},"modified":"2026-07-15T02:45:34","modified_gmt":"2026-07-15T02:45:34","slug":"potential-difference","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/electromagnetism\/potential-difference\/","title":{"rendered":"What Is Potential Difference (Voltage)?"},"content":{"rendered":"\n
Definition<\/div>

\n\nPotential difference is the energy transferred per unit charge between two points in a circuit, given by the formula V = W\/Q. It is measured in volts, where one volt equals one joule per coulomb. A potential difference of 6 V means every coulomb of charge passing between those two points transfers 6 joules of energy.\n\n<\/p><\/div>\n\n

A crow lands on a 25,000-volt power line and carries on preening. No spark, no smoke, nothing at all. Yet a 9 V battery \u2014 thousands of times feebler \u2014 will make your tongue tingle the moment you touch it across the terminals.<\/p>\n\n

The crow survives for one reason. Voltage is not something a wire contains; it exists between<\/em> two points, and the bird only ever touches one of them. Get that single idea straight and most of electricity stops being mysterious.<\/p>\n\n

What Is Potential Difference?<\/h2>\n\n

Potential difference is the amount of energy transferred per coulomb of charge moving between two points in a circuit. Say that slowly, because every word is doing work. It is energy, it is per coulomb<\/em>, and it is between two points<\/em>.<\/p>\n\n

Think of a cell as a pump that lifts charge to the top of a hill. Each coulomb arrives at the top carrying a fixed parcel of energy. As it travels down through a lamp, it hands that parcel over \u2014 and the lamp glows.<\/p>\n\n

The size of the parcel per coulomb is the potential difference. A 6 V supply hands every coulomb 6 joules. A 12 V supply hands every coulomb 12 joules, which is why the same lamp burns twice as brightly and twice as briefly.<\/p>\n\n

Notice what the definition never mentions: how much charge you move, or how fast. Potential difference is a property of the two points, not of the traffic between them. Move one coulomb or a million \u2014 the energy per<\/em> coulomb is unchanged.<\/p>\n\n

Potential Difference and Electric Potential<\/h3>\n\n

Electric potential is the energy per coulomb at a single<\/em> point, measured relative to some agreed zero. Potential difference is what you get when you subtract one from another: VAB<\/sub> = VA<\/sub> \u2212 VB<\/sub>.<\/p>\n\n

That agreed zero is usually the earth, which is why engineers call it “ground” and set it at 0 V. It is a convention, not a law of nature \u2014 much like measuring mountain heights from sea level rather than from the centre of the planet.<\/p>\n\n

The Potential Difference Formula<\/h2>\n\n

The potential difference formula is V = W\/Q \u2014 the energy transferred divided by the charge that transferred it.<\/p>\n\n

V = W \/ Q<\/div>\n\n

Every symbol, with its SI unit:<\/p>\n\n