Thursday, 20 December 2012

Basic Electrical Quantities

Basic quantities: current, voltage and power
Current: time rate of change of electric charge
  I = dq/dt 
1 Amp = 1 Coulomb/sec
Voltage:  electromotive force or potential, V 
1 Volt = 1 Joule/Coulomb = 1 N·m/coulomb
PowerP = I V 
1 Watt = 1 Volt·Amp = 1 Joule/sec

Active elements can generate energy
–Voltage and current sources
Passive elements cannot generate energy
–Capacitors and Inductors (but CAN store energy)
An independent source (voltage or current) may be DC (constant) or time-varying, but does not depend on other voltages or currents in the circuit.
The dependent source magnitude is a function of another voltage or current in the circuit.

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