1. Electrical Power:
Power is the rate at which electrical energy is used or produced. It tells you how much work an electrical device can do over time.
Formula: Power (P) is calculated as:
P = V x I
V is the voltage (how strongly the electricity is "pushed"),
I is the current (how much electricity flows),
P is power, measured in watts (W).
Example: A 60W light bulb uses 60 watts of power when it's on. If it's plugged into a 120V socket, the current flowing through it is:
I = P / V = 60W / 120V = 0.5A
2. Electrical Energy:
Energy is the total amount of work done over time. It tells you how much electricity was used in a certain period.
Formula: Energy (E) is calculated as:
E = P x t
P is power (in watts),
t is time (in hours, seconds, etc.),
E is energy, measured in watt-hours (Wh) or joules (J).
Example: If that 60W light bulb stays on for 5 hours:
E = 60W x 5h = 300Wh
This means the bulb used 300 watt-hours of energy.
3. Efficiency:
Efficiency measures how well a device converts the input energy into useful work without wasting too much.
Formula: Efficiency (n) is calculated as:
n = Pout / Pin x 100%
Pout is the useful power output,
Pin is the total power input.
Example: If an electric motor uses 100W of power but only 90W is used for work (like turning a fan), the efficiency is:
n = 90W / 100W x 100% = 90%
This means 10% of the power is wasted, likely as heat.
4. Power in AC Circuits:
In AC (alternating current) circuits, power isn’t always straightforward because of how voltage and current can get out of sync.
Real Power (P) is the actual useful power (measured in watts).
Reactive Power (Q) is power that doesn't do useful work but bounces back and forth in the circuit (measured in VAR).
Apparent Power (S) is the combination of both real and reactive power (measured in VA).
Power Factor: It tells you how efficiently the power is being used. A power factor of 1 means all the power is being used efficiently. Lower values mean some of the power is being wasted.
5. Power and Energy in Renewable Systems
Solar Panels: Convert sunlight into electricity. For example, a 200W solar panel that works for 5 hours produces:
E = 200W x 5h = 1000Wh = 1kWh
This means it generates enough energy to power a 1000W device for 1 hour.
In summary, power is about how fast you're using energy, and energy is about how much you've used over time. Efficiency helps you understand how much energy is actually doing useful work.
