A positive connection is one in which a change (increase or decrease) in some variable results in the same type of change (increase or decrease)in a second variable. The positive connection in the figure below for a cooling coffee cup implies that the hotter the coffee is the faster it cools.
The power consumption of small devices is usually measured in Watts, and the power consumption of larger devices is measured in kilowatts (kW), or 1,000 Watts. Electricity generation capacity is often measured in multiples of kilowatts, such as megawatts (MW) and gigawatts (GW).
Power is the rate at which energy is transferred. It is not energy but is often confused with energy. The watt is the most commonly used unit of measure for power. It measures the rate of energy transfer. Click on a scenario number above to begin the interactive explainer. A watt equals a joule per second. If a smart phone uses five joules of energy every second, then the power of the phone is five joules per second, or five watts. The animation above demonstrates the difference between energy and power. Each slide in the animation will transfer energy at different rates for five seconds.