Topic 9 Flashcards
First part of Chapter 11 (15 cards)
What is instantaneous power (p(t))? What is its formula?
Power (in Watts) at any instance of time. It is equal to the instantaneous voltage x instantaneous current.
What is average power?
Since instantaneous power is difficult to measure, it is normally more convenient to measure average power. It is the average of instantaneous power over one period.
T is period length.
What is a wattmeter?
Instrument for measuring average power.
Formula for average power using phasor voltage and current?
Where V is phasor voltage, and I* is the complex conjugate of the phasor current.
Power equations in terms of resistance?
How much power do inductors and capacitors absorb?
0
What is the maximum average power transfer formula?
How do you find maximum average power transfer for a pure RESISTIVE load?
RL = Zth
What value must the load impedance be equal to for maximum power transfer?
Maximum power is transferred to the load when load impedance is equal to the complex conjugate of the Thevenin impedance.
In AC circuits, what is Thevenin impedance?
Impedance is Rth (real part) + Xth (imaginary)
What is VL and IL?
Voltage and Current through/across a load. This is not the same as Vth, you must calculate it using voltage division.
What is effective or RMS value?
Only relevant for time-varying sources. The effective value of a periodic current is a DC current that can deliver the same average power to a resistor as the periodic current.
Formulas for the Root Means Square values for voltage and current?
Swap current for voltage values for Vrms.
How do you calculate average power using rms values?
Formulas for average power absorbed by a resistor using rms?
