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Single-Phase AC Power Analysis Quiz

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Questions and Answers

What is the formula for average power in an electrical circuit?

$P = \frac{1}{T} \int_{0}^{T} p(t) dt$ or $P = \frac{1}{T} \int_{0}^{T} v(t)i(t) dt$

What is the formula for average power in a resistive circuit?

$P = VI cos\Phi = I^2R

What is the formula for average power in a pure inductive or capacitive circuit?

$P = VI cos\Phi = 0

What type of load always absorbs power in an electrical circuit?

A resistive load (R) Signup and view all the answers

What type of load absorbs zero average power in an electrical circuit?

A reactive load (L or C) Signup and view all the answers

Explain the concept of average power and its measurement in electrical circuits.

The average power is the average of the instantaneous power over one period and can be calculated using the formula $P = \frac{1}{T} \int_{0}^{T} p(t) dt$. It is more convenient to measure than instantaneous power, and the wattmeter, the instrument for measuring power, responds to average power. Signup and view all the answers

Derive the expression for average power in electrical circuits using phasor notation.

The expression for average power in electrical circuits using phasor notation is given by $P = \frac{V_{rms}I_{rms}}{2} \cos(\theta_v - \theta_i)$, where $V_{rms}$ and $I_{rms}$ are the rms voltage and current, and $\theta_v$ and $\theta_i$ are the phase angles of the voltage and current, respectively. Signup and view all the answers

What is the average power in a resistive circuit and in a pure inductive or capacitive circuit?

In a resistive circuit, the average power is given by $P = V_{rms}I_{rms}\cos(\Phi)$, where $\Phi = 0$. In a pure inductive or capacitive circuit, the average power is zero, as $\Phi = \pm 90$ and $\cos(\Phi) = 0. Signup and view all the answers

What is the concept of complex power and how is it related to the average power in electrical circuits?

The complex power $S$ absorbed by the AC load is a combination of real power (average power) and reactive power. It is defined as $S = P + jQ$, where $P$ is the average power and $Q$ is the reactive power. Signup and view all the answers

What is the behavior of resistive and reactive loads in terms of power absorption?

A resistive load (R) always absorbs power, while a reactive load (L or C) absorbs zero average power. This is because the average power in a reactive load is dependent on the phase angle, leading to a power factor of zero. Signup and view all the answers