To calculate the current and voltage drop across the 11.2Ω resistor using Norton's theorem, we follow these steps:
Step 1: Find the Norton Current (IN)
To find IN, we remove the load resistor (Rload=11.2Ω) and place a short circuit across its terminals. Let the terminals be B and ground. This means the voltage at terminal B is 0V.
The circuit now consists of the 20V source, R1=20Ω, R2=12Ω, and R3=8Ω.
Let Node A be the junction between R1, R2, and R3.
When terminal B is shorted to ground, R2 is connected between Node A and ground, and R3 is also connected between Node A and ground. Thus, R2 and R3 are in parallel.
The equivalent resistance of R2∥R3 is:
R23=R2+R3R2×R3=12Ω+8Ω12Ω×8Ω=20Ω96Ω2=4.8Ω
The total current (Itotal) flowing from the source is through R1 and then through the parallel combination of R2 and R3:
Itotal=R1+R23V=20Ω+4.8Ω20V=24.8Ω20V=248200A=3125A
This current Itotal reaches Node A and splits between R2 and R3. The Norton current IN is the current flowing through the short circuit, which is the current that would flow through R2 in this configuration (since the short is across the terminals where Rload was, and R2 is connected to that node). Using the current divider rule:
IN=Itotal×R2+R3R3=3125A×12Ω+8Ω8Ω=3125A×208=3125A×52=3110A
IN≈0.3226A
Step 2: Find the Norton Resistance (RN)
To find RN, we turn off the independent voltage source (replace it with a short circuit) and look into the terminals where the load resistor was connected (terminals B and ground).
With the voltage source shorted, R1 is connected from Node A to ground. R3 is also connected from Node A to ground. So, R1 and R3 are in parallel.
R13=R1+R3R1×R3=20Ω+8Ω20Ω×8Ω=28Ω160Ω2=740Ω
Now, looking from terminals B to ground, R2 is in series with the parallel combination of R1 and R3.
RN=R2+R13=12Ω+740Ω=712×7+40Ω=784+40Ω=7124Ω
RN≈17.7143Ω
Step 3: Calculate the current through the load resistor (Iload)
Now we connect the load resistor Rload=11.2Ω in parallel with the Norton equivalent circuit (IN in parallel with RN). We use the current divider rule:
Iload=IN×RN+RloadRN
Iload=3110A×7124Ω+11.2Ω7124Ω
Convert 11.2Ω to a fraction: 11.2=10112=556.
Iload=3110A×7124+5567124=3110A×35124×5+56×77124
Iload=3110A×35620+3927124=3110A×3510127124
Iload=3110A×7124×101235=3110A×1012124×5
Iload=313726200A=78431550A
Iload≈0.1976 A
Step 4: Calculate the voltage drop across the load resistor (Vload)
Using Ohm's Law:
Vload=Iload×Rload
Vload=78431550A×11.2Ω=78431550A×556Ω
Vload=7843310×56V=784317360V
Vload≈2.213 V
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