Showing posts with label Laws. Show all posts
Showing posts with label Laws. Show all posts

Saturday, 2 December 2017

Kirchhoffs Circuit Law

Kirchhoffs Law
                     In 1845, a German physicist, Gustav Kirchhoff developed a pair or set of rules or laws which deal with the conservation of current and energy within electrical circuits. These two rules are commonly known as:

 Kirchhoffs Current Law, (KCL)

 Kirchhoffs Voltage Law, (KVL)

 Kirchhoffs Current Law, (KCL)
                                          Kirchhoffs Current Law or KCL, states that the “total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node“.
                                         In other words the algebraic sum of ALL the currents entering and leaving a node must be equal to zero, 
                          
                                              I(exiting) + I(entering) = 0

                                I2 + I4 + I5 + I6 + I3 + I1 = 0

Kirchhoffs Voltage Law, (KVL)
                                           Kirchhoffs Voltage Law or KVL, states that “in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop” which is also equal to zero.
                                         In other words the algebraic sum of all voltages within the loop must be equal to zero.
 
                                                  Image result for kvl

                                        
                                      VAB+VBC+VCD+VDA=0

    Sign Convention in Kirchhoff’s Rules:

1.    Move through EMF device in assumed direction of polarity (– to +):
                                                      e > 0

     2.    Move through EMF device in opposite direction of polarity (+ to –):
                                              e < 0
     3.    Move through resistor in assumed direction of current (with current   
         arrow):
                                                DV = –IR
     4.    Move through resistor in opposite direction of current (against current   
        arrow):
                                        DV = +IR
    5.    Move through capacitor from + plate to – plate (with E-field):
                                          DV = –q/C
  
    6.    Move through capacitor from – plate to + plate (against E-field):
                                DV = +q/C