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Joule per Second (J/s) - Unit Information & Conversion

Symbol:J/s
Plural:J/s
Category:Power

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What is a Joule per Second?

Joule per second (J/s) is exactly equal to 1 watt by definition. SI base unit of power. 1 J/s = 1 W exactly. Power = Energy per time. Used interchangeably with watt in physics, engineering.

History of the Joule per Second

Fundamental SI definition of power: 1 watt = 1 joule per second (adopted 1960). Named after James Watt. Defines relationship between energy (joules) and power (watts). Foundation of all power measurements.

Quick Answer

What is J/s? Joule per second (J/s) = 1 watt exactly by definition. SI unit of power. Power is energy transferred per unit time. 100W bulb uses 100 J/s. Used interchangeably with watt in scientific contexts. Use our power converter for conversions.

Definition

1 J/s = 1 W (exactly, by definition)

SI Definition of Watt: 1 W = 1 J/s = 1 kg⋅m²/s³

Common Uses

Physics: Fundamental power unit, teaching energy/power relationship. Engineering: Power calculations, energy transfer rates. Scientific: Research papers, technical specifications. Interchangeable: J/s and W used synonymously.

Real-World Examples

Power = Energy per Time

  • 100W light bulb: 100 J/s (uses 100 joules every second)
  • 1 kW heater: 1,000 J/s (1,000 joules every second)
  • Car engine (100 hp): 74,600 J/s = 74.6 kW
  • Nuclear reactor (1 GW): 1,000,000,000 J/s

Energy Consumption Examples

  • LED bulb (10W): Uses 10 J/s → 600 J/min → 36,000 J/hr
  • Laptop (50W): Uses 50 J/s → 180,000 J/hr
  • Microwave (1,000W): Uses 1,000 J/s → 3,600,000 J/hr = 3.6 MJ/hr

Human Power Output

  • At rest: 70-100 J/s (70-100 W)
  • Walking: 200-300 J/s (200-300 W)
  • Running: 600-1,000 J/s (600-1,000 W)
  • Cycling (pro): 300-500 J/s sustained (300-500 W)
  • Peak sprint: 1,500-2,000 J/s (1.5-2 kW)

Joule per Second Conversion Formulas

To Watt:

1 J/s = 1 W
Example: 5 J/s = 5 watts

To Milliwatt:

1 J/s = 1000 mW
Example: 5 J/s = 5000 milliwatts

To Kilowatt:

1 J/s = 0.001 kW
Example: 5 J/s = 0.005 kilowatts

To Megawatt:

1 J/s = 0.000001 MW
Example: 5 J/s = 0.000005 megawatts

To Gigawatt:

1 J/s = 1.0000e-9 GW
Example: 5 J/s = 5.0000e-9 gigawatts

To Horsepower:

1 J/s = 0.001341 hp
Example: 5 J/s = 0.006705 horsepower

To Metric Horsepower:

1 J/s = 0.00136 PS
Example: 5 J/s = 0.006798 PS

To Electric Horsepower:

1 J/s = 0.00134 hp(E)
Example: 5 J/s = 0.006702 hp(E)

To BTU per Hour:

1 J/s = 3.412142 BTU/h
Example: 5 J/s = 17.060708 BTU/h

To BTU per Minute:

1 J/s = 0.056869 BTU/min
Example: 5 J/s = 0.284345 BTU/min

To BTU per Second:

1 J/s = 0.000948 BTU/s
Example: 5 J/s = 0.004739 BTU/s

To Foot-pound per Second:

1 J/s = 0.737562 ft⋅lb/s
Example: 5 J/s = 3.687811 ft⋅lb/s

To Foot-pound per Minute:

1 J/s = 44.253729 ft⋅lb/min
Example: 5 J/s = 221.268645 ft⋅lb/min

To Calorie per Second:

1 J/s = 0.239006 cal/s
Example: 5 J/s = 1.195029 cal/s

To Kilocalorie per Hour:

1 J/s = 0.860421 kcal/h
Example: 5 J/s = 4.302103 kcal/h

To Ton of Refrigeration:

1 J/s = 0.000284 TR
Example: 5 J/s = 0.001422 TR

To Erg per Second:

1 J/s = 10000000 erg/s
Example: 5 J/s = 50000000 erg/s

Frequently Asked Questions

SI Definition: The watt is defined as one joule per second Dimensional analysis:

  • Energy: joules (J)
  • Time: seconds (s)
  • Power: energy/time = J/s Therefore: 1 W ≡ 1 J/s (definitional equality) Example: 100W device uses 100 J every second
  • 1 second: 100 J used
  • 10 seconds: 1,000 J used
  • 1 hour (3,600s): 360,000 J = 360 kJ = 0.1 kWh

Convert Joule per Second

Need to convert Joule per Second to other power units? Use our conversion tool.

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Joule per Second Quick Info

J/s
Symbol:J/s
Category:Power
System:Various
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