| Norton's TheoremNorton's Theorem states that it is possible 
                    to simplify any linear circuit, no matter how complex, to an 
                    equivalent circuit with just a single current source and 
                    parallel resistance connected to a load. Just as with 
                    Thevenin's Theorem, the qualification of "linear" is 
                    identical to that found in the Superposition Theorem: all 
                    underlying equations must be linear (no exponents or roots).
                     Contrasting our original example circuit 
                    against the Norton equivalent: it looks something like this:
                     
                      . . . after Norton conversion . . .  
                      Remember that a current source is a 
                    component whose job is to provide a constant amount of 
                    current, outputting as much or as little voltage necessary 
                    to maintain that constant current.  As with Thevenin's Theorem, everything in 
                    the original circuit except the load resistance has been 
                    reduced to an equivalent circuit that is simpler to analyze. 
                    Also similar to Thevenin's Theorem are the steps used in 
                    Norton's Theorem to calculate the Norton source current (INorton) 
                    and Norton resistance (RNorton).  As before, the first step is to identify the 
                    load resistance and remove it from the original circuit:  
                      Then, to find the Norton current (for the 
                    current source in the Norton equivalent circuit), place a 
                    direct wire (short) connection between the load points and 
                    determine the resultant current. Note that this step is 
                    exactly opposite the respective step in Thevenin's Theorem, 
                    where we replaced the load resistor with a break (open 
                    circuit):  
                      With zero voltage dropped between the load 
                    resistor connection points, the current through R1 
                    is strictly a function of B1's voltage and R1's 
                    resistance: 7 amps (I=E/R). Likewise, the current through R3 
                    is now strictly a function of B2's voltage and R3's 
                    resistance: 7 amps (I=E/R). The total current through the 
                    short between the load connection points is the sum of these 
                    two currents: 7 amps + 7 amps = 14 amps. This figure of 14 
                    amps becomes the Norton source current (INorton) 
                    in our equivalent circuit:  
                      Remember, the arrow notation for a current 
                    source points in the direction opposite that of 
                    electron flow. Again, apologies for the confusion. For 
                    better or for worse, this is standard electronic symbol 
                    notation. Blame Mr. Franklin again!  To calculate the Norton resistance (RNorton), 
                    we do the exact same thing as we did for calculating 
                    Thevenin resistance (RThevenin): take the 
                    original circuit (with the load resistor still removed), 
                    remove the power sources (in the same style as we did with 
                    the Superposition Theorem: voltage sources replaced with 
                    wires and current sources replaced with breaks), and figure 
                    total resistance from one load connection point to the 
                    other:  
                      Now our Norton equivalent circuit looks like 
                    this:  
                      If we re-connect our original load 
                    resistance of 2 Ω, we can analyze the Norton circuit as a 
                    simple parallel arrangement:  
                      As with the Thevenin equivalent circuit, the 
                    only useful information from this analysis is the voltage 
                    and current values for R2; the rest of the 
                    information is irrelevant to the original circuit. However, 
                    the same advantages seen with Thevenin's Theorem apply to 
                    Norton's as well: if we wish to analyze load resistor 
                    voltage and current over several different values of load 
                    resistance, we can use the Norton equivalent circuit again 
                    and again, applying nothing more complex than simple 
                    parallel circuit analysis to determine what's happening with 
                    each trial load.  
                      
                      REVIEW: 
                      Norton's Theorem is a way to reduce a 
                      network to an equivalent circuit composed of a single 
                      current source, parallel resistance, and parallel load.
                      
                      Steps to follow for Norton's Theorem: 
                      (1) Find the Norton source current by 
                      removing the load resistor from the original circuit and 
                      calculating current through a short (wire) jumping across 
                      the open connection points where the load resistor used to 
                      be. 
                      (2) Find the Norton resistance by removing 
                      all power sources in the original circuit (voltage sources 
                      shorted and current sources open) and calculating total 
                      resistance between the open connection points. 
                      (3) Draw the Norton equivalent circuit, 
                      with the Norton current source in parallel with the Norton 
                      resistance. The load resistor re-attaches between the two 
                      open points of the equivalent circuit. 
                      (4) Analyze voltage and current for the 
                      load resistor following the rules for parallel circuits.
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