Joule Calculator
Convert energy units and calculate work from force and distance
How to Use
- Select calculation mode: Energy conversion or Physics calculation
- For energy conversion: Enter value, select from/to units, and calculate
- For physics calculation: Enter force (newtons) and distance (meters)
- View results with conversion formulas and all energy unit equivalents
- Use the recalculate button to perform new calculations
What is a Joule?
A joule (J) is the SI unit of energy, work, and heat. It's defined as the amount of work done when a force of one newton is applied over a distance of one meter. The joule is named after James Prescott Joule, a British physicist who studied the relationship between heat and mechanical work.
The joule is a fundamental unit in physics and engineering, used to measure energy in all its forms: kinetic, potential, thermal, electrical, and chemical energy.
Common Energy Units
| Unit | Symbol | Joules Equivalent | Common Use |
|---|---|---|---|
| Joule | J | 1 J | SI base unit, physics |
| Calorie | cal | 4.184 J | Food energy, chemistry |
| Kilocalorie | kcal | 4,184 J | Food energy (Calorie) |
| Watt-hour | Wh | 3,600 J | Electrical energy |
| Kilowatt-hour | kWh | 3,600,000 J | Electricity bills |
| British Thermal Unit | BTU | 1,055.06 J | Heating/cooling |
| Electronvolt | eV | 1.602×10⁻¹⁹ J | Atomic physics |
| Foot-pound | ft·lb | 1.356 J | Mechanical work |
Work and Energy in Physics
In physics, work is defined as the transfer of energy that occurs when a force is applied to an object and the object moves in the direction of the force. The work-energy theorem states that the work done on an object equals the change in its kinetic energy.
The basic formula for work is: W = F × d × cos(θ), where W is work, F is force, d is distance, and θ is the angle between the force and displacement vectors. When the force and displacement are in the same direction, this simplifies to W = F × d.
Energy Conversion Examples
- 1 kWh = 3,600,000 J (typical household energy consumption)
- 1 food calorie = 4,184 J (energy in food)
- 1 BTU = 1,055.06 J (heating/cooling energy)
- 1 eV = 1.602×10⁻¹⁹ J (atomic energy levels)
- 1 ft·lb = 1.356 J (mechanical work)
Practical Applications
- Electrical energy: kWh for electricity bills, Wh for batteries
- Food energy: Calories for nutrition labels and diet planning
- Heating/cooling: BTU for HVAC systems and appliances
- Physics experiments: Joules for work and energy measurements
- Mechanical engineering: Foot-pounds for torque and work
- Atomic physics: Electronvolts for particle energies
Frequently Asked Questions
- What's the difference between a calorie and a kilocalorie?
- A calorie (cal) is a small unit of energy equal to 4.184 joules. A kilocalorie (kcal) is 1,000 calories and is often called a "Calorie" (capital C) on food labels. So 1 kcal = 1 Calorie = 4,184 J.
- How do I convert between electrical energy units?
- Electrical energy is commonly measured in watt-hours (Wh) or kilowatt-hours (kWh). 1 kWh = 1,000 Wh = 3,600,000 J. To convert from kWh to joules, multiply by 3,600,000. To convert from joules to kWh, divide by 3,600,000.
- What is work in physics and how is it calculated?
- Work is the transfer of energy when a force causes displacement. The basic formula is W = F × d, where W is work in joules, F is force in newtons, and d is distance in meters. Work is positive when force and displacement are in the same direction.
- Why are electronvolts used in atomic physics?
- Electronvolts (eV) are convenient for atomic and particle physics because they're much smaller than joules (1 eV = 1.602×10⁻¹⁹ J). This makes it easier to work with the tiny energies involved in atomic processes, chemical bonds, and particle interactions.
- How accurate are these energy conversions?
- The conversions use standard conversion factors that are accurate for most practical purposes. However, some conversions (like calories) may have slight variations depending on the specific definition used. For precise scientific work, always verify the exact conversion factors for your specific application.