Math Problem Statement

answer

Find Vout, write a formula for Vout, use Kirchhoff, Thevenin, Norton theorems, write the algebraic form, and learn about Cramer rule for the given AC circuit with resistors.

Solution

Let's analyze the circuit step by step to answer the questions in the image:

Circuit Overview:

You have a series-parallel AC circuit where:

  • Vin=10VrmsV_{\text{in}} = 10 \, \text{V}_{\text{rms}}, 50 Hz AC source.
  • The resistors are all 1 kΩ (there are five 1 kΩ resistors in total).
  • You need to find VoutV_{\text{out}} across the resistor at the far right of the circuit.

Step-by-Step Solutions:

  1. Find VoutV_{\text{out}}:

    To solve for VoutV_{\text{out}}, you need to calculate the equivalent resistance of the entire circuit first. Let's break the circuit down:

    • The first two resistors on the top are in series: Rseries1=1kΩ+1kΩ=2kΩR_{\text{series1}} = 1 \, \text{k}\Omega + 1 \, \text{k}\Omega = 2 \, \text{k}\Omega.
    • The middle resistor on the bottom (1 kΩ) is in parallel with the two series resistors: Rparallel=(Rseries1×1kΩ)(Rseries1+1kΩ)=(2×1)(2+1)=23kΩR_{\text{parallel}} = \frac{(R_{\text{series1}} \times 1 \, \text{k}\Omega)}{(R_{\text{series1}} + 1 \, \text{k}\Omega)} = \frac{(2 \times 1)}{(2 + 1)} = \frac{2}{3} \, \text{k}\Omega.
    • Now, add the last two resistors (both 1 kΩ) in series with this parallel combination: Rtotal=23kΩ+1kΩ+1kΩ=83kΩ2.67kΩ.R_{\text{total}} = \frac{2}{3} \, \text{k}\Omega + 1 \, \text{k}\Omega + 1 \, \text{k}\Omega = \frac{8}{3} \, \text{k}\Omega \approx 2.67 \, \text{k}\Omega.

    The total voltage across the circuit is 10 V. Using a voltage divider, you can calculate VoutV_{\text{out}}: Vout=Vin×RlastRtotal=10V×1kΩ83kΩ=10×38=3.75V.V_{\text{out}} = V_{\text{in}} \times \frac{R_{\text{last}}}{R_{\text{total}}} = 10 \, \text{V} \times \frac{1 \, \text{k}\Omega}{\frac{8}{3} \, \text{k}\Omega} = 10 \times \frac{3}{8} = 3.75 \, \text{V}.

    So, Vout3.75VV_{\text{out}} \approx 3.75 \, \text{V}.

  2. Write a formula for VoutV_{\text{out}}:

    General formula using a voltage divider: Vout=Vin×RlastRtotal,V_{\text{out}} = V_{\text{in}} \times \frac{R_{\text{last}}}{R_{\text{total}}}, where RtotalR_{\text{total}} is the equivalent resistance of the entire circuit.

  3. Use Kirchhoff, Thevenin, Norton:

    • Kirchhoff's Voltage Law (KVL): You can apply KVL around loops to verify that the sum of voltage drops equals VinV_{\text{in}}.
    • Thevenin's Theorem: You can reduce the left part of the circuit (left of the right-most resistor) into a Thevenin equivalent with a Thevenin voltage and Thevenin resistance.
    • Norton's Theorem: Similar to Thevenin’s, but you represent the circuit with an equivalent current source and parallel resistance.
  4. Write algebraic form for this:

    For Thevenin equivalent:

    • Thevenin voltage VthV_{\text{th}}: Calculate the open-circuit voltage at the point where the output resistor is connected.
    • Thevenin resistance RthR_{\text{th}}: This would be the equivalent resistance seen from the terminals of the output resistor with the source replaced by its internal resistance (AC source has an internal resistance of 0 for this problem).
  5. Learn about Cramer’s rule:

    Cramer’s rule is a method for solving systems of linear equations using determinants. It can be applied if you use mesh analysis to solve this circuit by forming simultaneous equations for each loop.


Questions to Explore Further:

  1. How does the frequency of the AC source affect the circuit if we consider capacitors or inductors?
  2. How do you apply Norton's Theorem to find the equivalent circuit?
  3. What is the advantage of using Thevenin’s Theorem over direct analysis?
  4. How does Kirchhoff’s Current Law (KCL) apply to the nodes in this circuit?
  5. How would the circuit change if you replaced one resistor with a capacitor?

Tip: Always remember to check your final answers for consistency by summing voltage drops (KVL) or currents (KCL) in the circuit!

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Math Problem Analysis

Mathematical Concepts

Electrical Circuit Analysis
Algebra
Linear Equations
Determinants

Formulas

Vout = Vin * (Rlast / Rtotal)
Rparallel = (R1 * R2) / (R1 + R2)
Rtotal = sum of resistances
Thevenin Voltage and Resistance
Kirchhoff's Voltage Law

Theorems

Kirchhoff's Voltage Law
Thevenin's Theorem
Norton's Theorem
Cramer's Rule

Suitable Grade Level

Undergraduate (Electrical Engineering)