Electric Resistance Converter
Convert between various units of electric resistance, including ohms, kilohms, megohms, and more.
About Electric Resistance Units
Electric resistance is a measure of how much a material opposes the flow of electric current. The SI unit of electrical resistance is the ohm (Ω), which represents the resistance of a conductor through which a current of one ampere flows when a potential difference of one volt is applied.
Common Electric Resistance Units
- Ohm (Ω): The SI unit of electric resistance. Named after German physicist Georg Simon Ohm.
- Milliohm (mΩ): Equal to 10-3 ohms. Used for measuring very small resistances like those in connectors and PCB traces.
- Microohm (μΩ): Equal to 10-6 ohms. Used in precision measurements of very low resistances like those in superconductors.
- Kilohm (kΩ): Equal to 103 ohms. Commonly used in electronics for resistors.
- Megohm (MΩ): Equal to 106 ohms. Used for high-resistance components and insulation measurements.
- Gigaohm (GΩ): Equal to 109 ohms. Used for extremely high-resistance measurements in specialized applications.
- Abohm: A unit in the CGS electromagnetic system, equal to 10-9 ohms.
- Statohm: A unit in the CGS electrostatic system, equal to approximately 9 × 1011 ohms.
Ohm's Law
The fundamental relationship between voltage (V), current (I), and resistance (R):
Where R is in ohms, V is in volts, and I is in amperes.
Resistivity and Resistance
The resistance of a specific conductor can be calculated using its resistivity (ρ), length (L), and cross-sectional area (A):
Where R is in ohms, ρ is in ohm-meters, L is in meters, and A is in square meters.
Typical Resistance Values
| Material/Component | Typical Resistance Range | Application/Notes |
|---|---|---|
| Superconductors (below critical temperature) | 0 Ω | MRI machines, particle accelerators |
| Copper wire (typical household) | 0.1 - 10 Ω | Electrical wiring |
| Standard resistors (electronics) | 1 Ω - 10 MΩ | Circuit components |
| Human body (hand to hand) | 1 kΩ - 100 kΩ | Varies with moisture, contact area |
| Electrical insulation | 1 MΩ - 10 TΩ | Electrical safety |
| Air (dry) | 1016 Ω·m (resistivity) | Electrical isolation |
Resistors in Circuits
Series Connection
When resistors are connected in series, their resistances add:
Parallel Connection
When resistors are connected in parallel, their conductances add:
Electric Resistance Applications
- Electronics: Resistors are fundamental components in electronic circuits used to control current flow, divide voltage, and provide biasing.
- Heating Elements: Electric heaters use resistive elements to convert electrical energy to heat (Joule heating).
- Sensors: Many sensors like thermistors, strain gauges, and photoresistors work based on changes in electrical resistance.
- Power Transmission: Minimizing resistance in power lines is crucial for efficient electricity distribution.
- Electrical Safety: Insulation resistance measurements ensure electrical systems are safely isolated.
- Medical Devices: Bioelectrical impedance analysis uses resistance measurements to estimate body composition.
Power Dissipation in Resistors
Power (P) dissipated in a resistor is related to current (I) and resistance (R) by:
Where P is in watts, I is in amperes, R is in ohms, and V is in volts.