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Circuits 2 Overview

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Circuits 2 Overview

January 11, 2005

Harding University

Jonathan White

- 3 tests and a comprehensive final
- The first test should be easy if you remember last semester.

- Homework for each chapter
- Small quizzes to reinforce new concepts or if I think you are sleeping
- Lab every Thursday except tomorrow
- Some labs will be for presentations
- Some may be needed for test review

- Final projects:
- Team build of an FM transmitters
- Team presentation and report on any circuits topic

- After the first 3 chapters, the material covered is more difficult due to the math involved.
- Also, some memorization of formulas will be required.

- Impedance: ratio of phasor voltage to phasor current.
- Z = V/I -- similar to Ohm’s Law, R=V/I
- Impedances are combined exactly like resistors.
- For resistors, Z = R
- For inductors, Z = jwL
- For capacitors, Z = 1/(jwC)

- To solve AC circuits, convert every element to an impedance value and treat like a resistor.

Simplify and write in rectangular and polar form:

- Find I0 in the circuit below:

Obtain Zin for the circuit below:

- Nodal analysis
- Mesh analysis
- Superposition
- Source transformation
- Thevenin/Norton equivalents
- Should be a good review of last semester. Make sure you can do nodal analysis.

- Use nodal analysis to find vo in the circuit below:

Find the Thevenin equivalent from a to b

Find the mesh currents if v1 = 10cos(4t) V and v2 = 20cos(4t – 30o) V

- Power in a circuit is still p = v*I
- However, the power in an AC circuit changes continually. We use average power.
- PAVG = ½ VmImcos(θv – θi)

- However, the power in an AC circuit changes continually. We use average power.
- Resistive loads absorb power all the time. Reactive loads don’t.
- RMS values of currents/voltages
- Power factors

Find the average power absorbed by each element if vs = 8cos(2t – 40o) V

Find the RMS value of the waveform below:

- Used in high power applications
- Used in power generation plants
- Used in alternators/generators
- Typically consists of 3 voltage sources spread out by 120o in phase
- Wye or Delta Connections

- Table 12.1 (page 518) summarizes about everything about 3 Phase circuits.

For the - circuit below, calculate the phase and line currents:

- Also known as transformers
- You’ll be spending about 2 months on this in physics
- The number of windings in the coils affect the produced voltage and current.
- This is the summary for this chapter.

Find the average power delivered to the 4 Ohm resistor:

- Variation in behavior of a circuit with a change in signal frequency.
- Bode plots
- Only a little

- Resonance
- We’ve done this before in lab

- Quality factor and bandwidth
- Passive filters:
- Lowpass/HighPass/Bandpass/Bandstop

- Active filters with Op Amps
- This is a very long, but very important chapter.
- It is also very understandable and useful.

Calculate the resonant frequency, the quality factor, and the bandwidth for the circuit below:

- A way of solving sinusoidal and non-sinusoidal problems
- Lets use do algebra instead of calculus
- Make the RLC problems just a few steps instead of 15.

- Works by transferring the whole problem from the time domain into the frequency domain, solving the problem algebraically, and then doing an inverse Laplace transform at the end to get back to the time domain.
- Laplace makes solving complex problems much easier

- Covered in the differential equations class.

Find the Laplace Transform of:

f(t) = te-2tu(t – 1)

Find the inverse Laplace transform of:

Find v0 using the Laplace Method:

- These are difficult, and we will only cover them if we have time at the end of class
- They are covered in the differential equations class and in control systems.

- Fourier transforms are used to express non-sinusoidal sources as an infinite sum of sinusoids.
- We can then apply the methods we’ve used in AC analysis.

- Page 764 has a great picture of what the Fourier transform does.