What Is the Resistance and Power for 120V and 5A?

With 120 volts across a 24-ohm load, 5 amps flow and 600 watts are dissipated. These four values (voltage, current, resistance, and power) are the foundation of every electrical calculation on this site.

120V and 5A

24 Ω | 600 W

Voltage (V)120 V

Current (I)5 A

Resistance (R)24 Ω

Power (P)600 W

Volts

Amps

Ohms

Watts

600

Formulas & Step-by-Step

Resistance

R = V ÷ I

120 ÷ 5 = 24 Ω

Power

P = V × I

120 × 5 = 600 W

Verification (alternative formulas)

P = I² × R

5² × 24 = 25 × 24 = 600 W ✓

P = V² ÷ R

120² ÷ 24 = 14,400 ÷ 24 = 600 W ✓

Circuit Analysis

Heat Dissipation

This circuit dissipates 600 watts of power as heat. In a resistor, all electrical energy at steady state converts to thermal energy. The actual component power rating needs headroom above this steady-state figure, but the specific derating depends on resistor type (carbon-comp, metal-film, wirewound each behave differently), ambient temperature, airflow or heat-sinking, and whether the load is continuous or pulsed. Check the resistor datasheet for the manufacturer-specific derating curve rather than applying a blanket margin.

If You Change the Resistance

Resistance	Current	Power	Change
12 Ω	10 A	1,200 W	Lower R = more current
18 Ω	6.67 A	800 W	Lower R = more current
24 Ω	5 A	600 W	Current
36 Ω	3.33 A	400 W	Higher R = less current
48 Ω	2.5 A	300 W	Higher R = less current

Same Resistance at Different Voltages

Holding the resistance constant at 24Ω, here is how current and power scale with source voltage. This is a reference table, not a set of separate circuit scenarios: each row is the same resistor under a different applied voltage.

Voltage	Current (at 24Ω)	Power
5V	0.2083 A	1.04 W
12V	0.5 A	6 W
24V	1 A	24 W
48V	2 A	96 W
120V	5 A	600 W
208V	8.67 A	1,802.67 W
230V	9.58 A	2,204.17 W
240V	10 A	2,400 W
480V	20 A	9,600 W

Related Calculations

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Frequently Asked Questions

What is the resistance for 120V and 5A?expand_more

R = V ÷ I = 120 ÷ 5 = 24 ohms.

Does Ohm's Law work for AC circuits?expand_more

For purely resistive loads, yes. For reactive loads, use impedance (Z) instead of resistance (R). Z includes both resistance and reactance, and the V/I phase shift shows up in power factor.

What determines wire size for 5A?expand_more

Wire sizing for a given current is not an Ohm's Law calculation. It depends on run length, source voltage, voltage-drop target, conductor material, insulation and termination temperature rating, cable type, and ambient and bundling conditions. The dedicated wire-size calculator takes those variables as input.

How are voltage, current, resistance, and power related?expand_more

Ohm's Law (V = IR) and the power equation (P = VI) connect all four. Given any two, you can calculate the other two.

What are all 12 Ohm's Law formulas?expand_more

V=IR, V=P/I, V=√(PR) | I=V/R, I=P/V, I=√(P/R) | R=V/I, R=V²/P, R=P/I² | P=VI, P=I²R, P=V²/R.

This calculator provides estimates for reference purposes only. Always consult a licensed electrician and verify compliance with the National Electrical Code (NEC) and local electrical codes before performing any electrical work.