Formula Used
This calculator supports several standard power equations.
- Work and time: P = W / t
- Energy and time: P = E / t
- Linear motion: P = Fv cos(theta)
- Electrical real power: P = VI × PF
- Resistance with current: P = I²R
- Resistance with voltage: P = V² / R
- Rotational power: P = tau × omega
- Lifting power: P = mgh / t
- Useful output power: Pout = Pin × efficiency / 100
How to Use This Calculator
- Select the formula that matches your known values.
- Enter only the values needed for that formula.
- Use standard units for direct watt output.
- Set decimal places for the final table.
- Press Calculate Power to view results above the form.
- Use CSV or PDF buttons to save the current calculation.
Example Data Table
| Case | Known Values | Formula | Power |
|---|---|---|---|
| Work rate | 500 J, 10 s | P = W / t | 50 W |
| Energy transfer | 1200 J, 10 s | P = E / t | 120 W |
| Linear motion | 100 N, 2 m/s, 0° | P = Fv cos(theta) | 200 W |
| Electric circuit | 120 V, 5 A, PF 1 | P = VI × PF | 600 W |
| Resistive load | 5 A, 24 ohms | P = I²R | 600 W |
| Rotating shaft | 40 N·m, 15 rad/s | P = tau × omega | 600 W |
Power in Physics
Power tells how fast work is done or energy changes. It connects force, motion, heat, electricity, and rotating machines. A high power value means energy moves quickly. A low value means the same energy transfer takes more time. This calculator helps compare common formulas without switching tools.
Why Power Matters
In mechanics, power explains engines, lifting systems, pumps, athletes, and moving loads. Work divided by time gives average power. Force times velocity gives useful power for steady motion. Torque times angular speed gives shaft power for motors, wheels, and fans. Each method uses the same unit, the watt, when standard units are used.
Electrical Power
Electrical power can be found from voltage and current. It can also be found from current and resistance, or voltage and resistance. These forms come from Ohm law. They are helpful when only two circuit values are known. The calculator also converts watts to kilowatts, horsepower, BTU per hour, and foot pounds per second.
Efficiency and Losses
Real systems waste energy through heat, friction, vibration, sound, and electrical resistance. Input power is usually higher than output power. Efficiency compares useful output with total input. The loss value shows wasted power. This is useful for checking motors, heaters, inverters, tools, and lab equipment.
Using Results Carefully
Good inputs give useful answers. Match units before entering values. Use joules for energy, seconds for time, newtons for force, meters per second for velocity, volts for voltage, amperes for current, ohms for resistance, newton meters for torque, and radians per second for angular speed. Convert minutes or hours to seconds when needed. Because power is a rate, negative signs may show direction or energy leaving a chosen system. This tool reports magnitude values for planning, while notes explain context. Always record assumptions with the answer for traceable calculations.
Practical Uses
Students can verify homework steps. Teachers can prepare examples. Technicians can estimate loads. Designers can compare machines. The table helps users see sample values before testing their own data. CSV export stores numeric records. PDF export creates a simple report for sharing or printing. The calculator is not a safety approval tool. Critical electrical or mechanical designs should be checked by qualified professionals and current standards.
FAQs
What is the basic formula for power?
The basic formula is P = W / t. Power equals work divided by time. When work is measured in joules and time in seconds, the result is watts.
Can power also be calculated from energy?
Yes. Use P = E / t when energy transfer is known. Energy and work both use joules, so both equations produce watts when divided by seconds.
Which electrical power formula should I use?
Use P = VI when voltage and current are known. Use P = I²R when current and resistance are known. Use P = V² / R when voltage and resistance are known.
What does power factor mean?
Power factor adjusts apparent power into real power for AC circuits. A value of 1 means the load uses all apparent power as real power.
How is rotational power calculated?
Rotational power is P = tau × omega. Torque must be in newton meters. Angular speed must be in radians per second for watts.
Why can force velocity power be negative?
It can be negative when force acts against motion. This often means braking, resisting, or absorbing energy instead of delivering it.
What is power loss?
Power loss is input power minus useful output power. It represents energy wasted through heat, friction, sound, vibration, or electrical resistance.
Can I save my calculation?
Yes. Press Download CSV for spreadsheet data. Press Download PDF for a simple printable report with formula, result, conversions, steps, and notes.