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OHM - KIRCHHOFF - NORTON

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OHM'S LAW

 
Ohm's Law relates the three fundamental electrical quantities: voltage, current and resistance. Power relationships are also given.

V = I · R     I = V     R = V
                     R           I

P = I · V     P = I2 · R     P = V2
                                              
R

I = Current (A)
P = Power (W)
R = Resistance (
W)
V = Voltage (V)

                       

KIRCHHOFF'S LAWS

  

Kirchhoff's Current (1st) Law

Kirchhoff's Voltage (2nd) Law

The current flowing into a node or branching point is equal to the sum of the individual currents leaving the node or branching point.

The algebraic sum of all the voltages around any closed path in a circuit equals zero.
 

                             

NORTON EQUIVALENTS

 

The Norton Equivalent of a circuit consists of a Norton current source in parallel with a Norton resistor and is valid for any load. In AC circuits a Norton equivalent circuit is valid for a single frequency.

Original Circuit

Norton Equivalent Circuit

The Norton current is the short-circuit current at the output - the same as what is calculated for the Thévénin short-circuit current (see Thévénin Equivalent page).
The Norton resistance is the same as the Thévénin resistance.
 

THÉVÉNIN EQUIVALENT

 

The Thévénin Equivalent of a circuit consists of a Thévénin voltage source in series with a Thévénin resistor and is valid for any load. In AC circuits a Thévénin equivalent circuit is valid for a single frequency.

The Thévénin voltage is the open circuit voltage at the output. calculation is straightforward node or loop circuit analysis. Using loop analysis:

Voc:  [8 * I1] + [(8+2+6) * I2] - [6 * I3] = 1 A

I2 = ½A ==> Voc = ½A * 6 W = 3 V = Vth

Calculate the Thévénin resistance from the open circuit voltage and the short circuit current
(set RL = 0 and solve for I3) using Ohm's Law.

Rth = Voc / Isc = 3 V / [(4/9) A] = 27 / 4 W = Rth

 

CURRENT CONVERSIONS

 

Standard unit = Ampere (A)

 
  abampere ampere statampere
1 abA = 1 10 2.998 * 1010
1 A = 0.1 1 2.998 * 109
1 statA = 3.336 * 10-11 3.336 * 10-10 1
 

POTENTIAL CONVERSIONS

 

Standard unit = Volt (V)

 
  abvolt volt statvolt
1 abV = 1 10-8 3.336 * 10-11
1 V = 108 1 3.336 * 10-3
1 statV = 2.998 * 1010 299.8 1