Ohm's Law & DC/AC Electrical Power Calculator

Calculate exact Voltage (V), Current (I), Resistance (R), and Power (P) across DC and single-phase AC circuits using the 12-formula Ohm's Law Wheel with thermal copper resistance shift.

Known Circuit Parameter Pair (Wheel of Equations)

Voltage (V) (Volts)

Resistance (R) (Ohms)

AC Power Factor (cos θ)1.00 (Pure DC/Resistive)

Copper Conductor Temp (°C)20°C (Standard Room Temp)

Engineering & Appliance Circuit Presets

⚡ Estimate-First Circuit Intuition Challenge

Before checking the table below, can you guess the resulting Current (Amps) for this exact circuit setup?

Voltage (V)

12 V

Current (I) - DC/Resistive

3 A

Resistance (R) @ 20°C Base

4 Ω

Active Power (P)

36 W

AC Impedance & Copper Thermal Shift Analysis

AC Apparent Power (S = P / PF)36 VA

AC RMS Current (at PF 1.00)3 A

Hot Copper Resistance (20°C)4 Ω

Hot Conductor Current (20°C)3 A

Step-by-Step Mathematical Walkthrough

Step 1: Determine all 4 primary Ohm/Joule parameters from known pair

I = V / R = 12 / 4 = 3 A; P = V × I = 36 W

Step 2: Single-Phase AC Power Factor Adjustment (PF = cos θ = 1.00)

PF = 1.0 (Purely resistive or DC load) → True Power P = Apparent Power S = 36 VA; AC RMS Current = 3 A

Step 3: Copper Conductor Thermal Resistance Shift at 20°C (Base 20°C, α = 0.00393 /°C)

R_T = 4 Ω × [1 + 0.00393 × (20 - 20)] = 4 Ω → Hot Current I_hot = 3 A

About the Ohm's Law Calculator

Ohm's Law defines the relationship between voltage, current, and resistance in an electrical circuit. Formulated by the German physicist Georg Ohm, it is the foundational rule of electrical engineering, electronics design, and circuit diagnostics.

Mathematical Formula & Logic

The primary mathematical expression is:

V = I × R

Where:
- V = Voltage in Volts (V)
- I = Current in Amperes (A)
- R = Resistance in Ohms (Ω)

Additionally, Power (P) in Watts (W) can be calculated using:
P = V × I  or  P = I² × R  or  P = V² / R

Step-by-Step Example

Calculate the current flowing through a 10 Ω resistor when connected to a 12V battery: I = V / R I = 12V / 10 Ω = 1.2 Amperes.

Reference Data & Values

metric	unit	formula	description
Voltage (V)	Volts (V)	V = I × R	Electrical potential difference
Current (I)	Amperes (A)	I = V / R	Flow of electric charge carriers
Resistance (R)	Ohms (Ω)	R = V / I	Opposition to charge flow
Power (P)	Watts (W)	P = V × I	Rate of electrical energy dissipation

Frequently Asked Questions

What is the physical meaning of Ohm's Law?＋

Ohm's Law states that the current passing through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them.

Does Ohm's Law apply to all circuits?＋

No. Ohm's law only applies to linear, ohmic conductors (like standard metal resistors) under constant temperature. It does not apply to non-ohmic components like diodes, transistors, or gas discharge tubes where resistance changes with voltage.

How does temperature affect resistance?＋

In most metals, electrical resistance increases as temperature rises because thermal agitation increases electron collisions. In semiconductors, resistance decreases as temperature rises because more charge carriers are freed.