Basic Concept & Basic Laws

Basic Concept & Basic Laws

1)  Charge: Charge is an electrical properties of the atomic particles of which matter consists.

                             Charge of electron is 1.602*10^-19 C.

2)  Current: The time rate of change of charge, measured in Amperes (A), mathematically,                                             
                                                  

3)  Voltage: The energy required to move a unit charge through an element, measured in volts (V) is called voltage.

4)   Power: This is the time rate of expending or absorbing energy, measured in watts (W), mathematically,

                                             

Plus Sign: Power is absorbed by the element (resistor, inductor).

Minus Sign: Power is supplied by the element (battery, generator).

If the current enters through the positive polarity of the voltage, then element is absorbing power. 
If the current enters through the negative polarity of the voltage, then element is delivering power.