Ohm's Law
Voltage-current-resistance relation.
What does Ohm's Law mean?
Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. It states that the current flowing through a conductor is directly proportional to the voltage across it and inversely proportional to the resistance. This law is essential for designing circuits, selecting components, and troubleshooting electrical systems.
How to calculate Ohm's Law
Ohm's Law is expressed as V = I × R. From this, you can derive: Current (I) = V / R, and Power (P) = V × I = V² / R. For example, if you have a 12 V battery connected to a 100 Ω resistor, the current is 12 / 100 = 0.12 A (120 mA), and the power dissipated is 12² / 100 = 1.44 W.
FAQ
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance. The formula is V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms.
Voltage is measured in volts (V), current in amperes or amps (A), and resistance in ohms (Ω). Power, which can be derived from Ohm's Law, is measured in watts (W). For small values, milliamps (mA) and kilohms (kΩ) are commonly used.
Power can be calculated using P = V² / R, where P is power in watts, V is voltage in volts, and R is resistance in ohms. This is derived by substituting I = V / R into the power formula P = V × I.
Ohm's Law applies to ohmic (linear) conductors where resistance remains constant regardless of voltage. Many real-world components like resistors follow this law. However, non-ohmic devices such as diodes, transistors, and thermistors have variable resistance and do not strictly follow Ohm's Law.
If resistance approaches zero (a short circuit), the current becomes extremely high, which can damage components or cause fires. Circuit protection devices like fuses and circuit breakers are used to prevent damage from excessive current caused by very low resistance paths.
Related calculators
- Force— Mass times acceleration.
- Kinetic Energy— Energy of motion.
- Density— Mass per volume.
- Pressure— Force per area.