P=W/t
where:
- P is power,
- W is work done or energy transferred,
- t is the time taken.
For example, if a force F is applied to move an object a distance d in time t, the work done (W) is given by W=F⋅d. Substituting this into the power equation, we get:
P = F⋅d/t
This equation shows that power is directly proportional to force, distance, and inversely proportional to time. The unit of power in the International System of Units (SI) is the watt (W), where 1 watt is equal to 1 joule per second.
Daily Life Examples
- Turning on a 60-watt light bulb for 2 hours consumes 60 W×2 h =120Wh of electrical energy.
- A car engine might produce 150 horsepower (1 horsepower ≈ 745.7 watts) to move the vehicle.
- A cyclist might generate around 100 watts of power while riding.
- A microwave oven operating at 800 watts for 5 minutes consumes 800 W×5 min=4000 of electrical energy.
- Climbing stairs might require an average power output of 200 watts.
- A hydroelectric power plant might generate 1,000 megawatts (1 MW = 1,000,000 W) of power.
- A treadmill might consume 500 watts of electrical power.
- An air conditioning unit might consume 1,500 watts of power per hour.
- An electric guitar amplifier might have a power rating of 50 watts.
- A typical smartphone charger may provide 10 watts of power.
- A manufacturing machine might require 50 kilowatts (1 kW = 1,000 W) of power.
How much in One Watt in Daily Life?
One watt (1 W) is the unit of power in the International System of Units (SI). It is defined as the rate at which work is done or energy is transferred, equivalent to one joule per second. In mathematical terms, one watt is represented as:
1 W=1 J/s
This means that a device consuming one watt of power will use one joule of energy every second.
While one watt (1 W) is a small unit of power, there are practical examples in daily life where this amount of power might be relevant. Here are a few examples:
- A typical LED light bulb might have a power rating of 7-10 watts. Leaving a single 10-watt LED bulb on for one hour consumes 10 watt-hours (Wh) of energy.
- Charging a smartphone with a standard charger typically involves using 5-10 watts. If you charge your phone for one hour, it consumes 5-10 Wh of energy.
- The average power output for a person doing moderate physical activity might range from 50 to 200 watts.
Difference Between Power and Energy
| No. | Power | Energy |
|---|---|---|
| 1. | Rate at which work is done | Capacity to do work |
| 2. | Unit: Watt (W) | Unit: Joule (J) |
| 3. | P=Et | E=P×t |
| 4. | Example: 60W light bulb | Example: 100W for 10s = 1000J |
| 5. | Measures how quickly energy is used/produced | Measures total capacity to do work |
| 6. | A 50W device for 2 hours consumes 100Wh of energy | Operating a 75W appliance for 5 hours consumes 375Wh of energy |