Example #2 Connect stereo to speakers. (a) If each wire must be 20m long, what diameter copper wire should be used to keep the resistance less than 0.10 Ω? (b) If the current is 4.0A, what is the potential difference across each wire?
Electric energy Energy transformation between electric and other forms are very common Motors transform electric energy into mechanical energy In electric heaters and hair dryers, electric energy is transformed into thermal energy In a lightbulb, electric energy is transformed into light and thermal energy
Electric power The electric power transformed by any device is P is electric power I is current V is potential difference The unit of electric power is Watt (W) For a resistance R, we have
Example #3 Calculate the resistance of a 40-W automobile headlight designed for 12V.
Alternating current The voltage and current produced by an electric generator are sinusoidal V 0 is the peak voltage I 0 is the peak current The frequency f is the number of complete oscillations per second, and