{"id":215,"date":"2026-06-11T23:17:30","date_gmt":"2026-06-11T23:17:30","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=215"},"modified":"2026-06-11T23:17:31","modified_gmt":"2026-06-11T23:17:31","slug":"ohms-law","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/electromagnetism\/ohms-law\/","title":{"rendered":"What Is Ohm’s Law?"},"content":{"rendered":"\n
Definition<\/div>

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Ohm’s law states that the electric current through a conductor is directly proportional to the voltage across it, provided temperature and other physical conditions stay constant. Written as V = IR, it links voltage (volts), current (amperes) and resistance (ohms): voltage equals current multiplied by resistance. It is the foundation of almost all circuit analysis.<\/p>\n<\/p><\/div>\n\n

Flick a dimmer switch and a lamp fades; turn it back and the room brightens. Nothing about the bulb changed \u2014 you changed the circuit, and the current obediently followed. That obedience has a name.<\/p>\n\n

Every charger, kettle, fuse and phone in your house is designed around one tidy relationship between voltage, current and resistance. Get comfortable with it and circuits stop being mysterious. That relationship is Ohm’s law.<\/p>\n\n

What Is Ohm’s Law?<\/h2>\n\n

Picture water in a pipe. Pressure pushes the water along, the pipe’s narrowness fights back, and the flow rate is the result of that tug-of-war. Electricity behaves the same way: voltage is the push, resistance is the fight, and current is the flow you actually get.<\/p>\n\n

Ohm’s law makes that picture precise. For many conductors held at a steady temperature, the current I<\/em> is directly proportional to the potential difference V<\/em> across them. Double the voltage and the current doubles; halve it and the current halves.<\/p>\n\n

The constant linking them is the resistance R<\/em> \u2014 a measure of how strongly the material opposes the flow of charge. A short, fat copper wire barely resists at all. A long, thin nichrome wire resists fiercely, which is exactly why heaters are made from it.<\/p>\n\n

The law is named after Georg Simon Ohm, a German physicist who was teaching school in Cologne when he published his careful wire experiments in 1827. His reward, eventually, was the SI unit of resistance \u2014 the ohm (\u03a9) \u2014 carrying his name.<\/p>\n\n

\n \"Georg\n
Georg Simon Ohm (1789\u20131854), whose 1827 wire experiments revealed the law that now bears his name.<\/figcaption>\n<\/figure>\n\n

One honest caveat before the maths. Ohm’s law is an empirical relation<\/strong> \u2014 a pattern found by experiment \u2014 not a fundamental law of nature like conservation of energy. Plenty of materials obey it beautifully; some important ones don’t, and we will meet them below.<\/p>\n\n

The Ohm’s Law Formula: V = IR<\/h2>\n\n

Here it is \u2014 three letters that run the electrical world.<\/p>\n\n

V = I \u00d7 R<\/div>\n\n