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Overview
Ohm's law is one of the basic relationships in circuit physics. It states that current through an ohmic component is proportional to the voltage across it and inversely related to resistance. It is widely used to analyze simple circuits, resistors, electrical power, and device behavior.
Core Relationship
Ohm's law connects voltage, current, and resistance. Increasing voltage increases current if resistance stays constant. Increasing resistance decreases current if voltage stays constant.
Ohmic Materials
An ohmic material or component follows Ohm's law over the range being studied. Many resistors approximate ohmic behavior.
Non-Ohmic Devices
Not all devices obey Ohm's law in a simple way. Diodes, light bulbs, semiconductors, and many electronic components may have nonlinear current-voltage relationships.
Units
Voltage is measured in volts, current in amperes, and resistance in ohms. Unit consistency is essential for circuit calculations.
Current-Voltage Graphs
An ohmic resistor has a straight-line current-voltage graph. The slope or inverse slope relates to resistance depending on which quantity is plotted on each axis.
Use in Circuit Analysis
Ohm's law helps find unknown voltage, current, or resistance in circuit branches and components.
Connection to Electrical Power
Ohm's law can be combined with electrical power relationships to calculate energy transfer rates in resistive elements.
Common Mistakes
A common mistake is applying Ohm's law to every electrical device without checking whether the device behaves ohmically.
Why This Matters in Physics
Ohm's law provides a practical foundation for circuits, electronics, power systems, measurement, troubleshooting, and electrical safety.