Electric power
We buy electric energy (E)
Power (P): is the amount of electric energy used per unit time
unit for Power: J/s--> Watts (W)
electric devices in the house are rated by their power usage
light bulbs:60, 75 or 100 W; washer: W etc….
Electric power through a portion of a circuit can be calculated as:
V: the voltage between the sides, I the current which is flowing, R the resistance:
The amount of used electric energy: E=P.t (can be measured in J, or in kWh (kilowatt-hour)-- more convenient
minimizing electric energy loses in the wires: (making R or I small)
sending the same amount of energy with small I (increasing V--> transformers)