Ohms Law Calculator
Ohms Law Formulas
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Understanding Ohms Law
The Fundamental Law
Ohms Law describes the relationship between voltage, current, and resistance in an electrical circuit. Discovered by Georg Ohm in 1827, it states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.
Ohms Law Formula
All Formulas
| Find | Given | Formula |
|---|---|---|
| Voltage (V) | I, R | V = I x R |
| Voltage (V) | P, I | V = P / I |
| Voltage (V) | P, R | V = sqrt(P x R) |
| Current (I) | V, R | I = V / R |
| Current (I) | P, V | I = P / V |
| Current (I) | P, R | I = sqrt(P / R) |
| Resistance (R) | V, I | R = V / I |
| Resistance (R) | P, I | R = P / I^2 |
| Power (P) | V, I | P = V x I |
| Power (P) | V, R | P = V^2 / R |
| Power (P) | I, R | P = I^2 x R |
Understanding the Units
Voltage (V)
- Unit: Volt (V)
- Electrical pressure/potential
- Like water pressure in a pipe
- Household: 120V or 240V
Current (I)
- Unit: Ampere (A)
- Flow rate of electrons
- Like water flow volume
- 1 A = 1 Coulomb/second
Resistance (R)
- Unit: Ohm (omega)
- Opposition to current flow
- Like pipe friction
- Depends on material & size
Power (P)
- Unit: Watt (W)
- Rate of energy transfer
- Heat generated in circuit
- 1 W = 1 J/s
The Water Analogy
Think of electricity like water in pipes. Voltage is the water pressure, current is the flow rate, resistance is the pipe friction, and power is the work the water can do. High pressure (voltage) with a wide pipe (low resistance) means lots of flow (current).
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that current (I) equals voltage (V) divided by resistance (R): I = V/R. It describes the fundamental relationship between electrical properties. Rearranged: V = I x R, or R = V / I.
How do I calculate power in a circuit?
Power (P) in watts equals voltage times current: P = V x I. Alternative formulas: P = I² x R (using current and resistance) or P = V²/R (using voltage and resistance).
What happens if resistance increases?
With constant voltage, increasing resistance decreases current (I = V/R). This is why dimmer switches work - they add resistance to reduce current flow through a light bulb, making it dimmer.
What are volts, amps, and ohms?
Volts measure electrical pressure (potential difference). Amps measure current flow (electrons per second). Ohms measure resistance (opposition to flow). Think of water: voltage is pressure, current is flow rate, resistance is pipe friction.