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(II) For a time-dependent voltage \(V(t),\) which is periodic with period \(T,\) the rms voltage is defined to be \(V_{\mathrm{rms}}=\left[\frac{1}{T} \int_{0}^{T} V^{2} d t\right]^{\frac{1}{2}} .\) Use this definition to determine \(V_{\mathrm{rms}}\) (in terms of the peak voltage \(V_{0}\) ) for \((a)\) a sinusoidal voltage, i.e., \(V(t)=V_{0} \sin (2 \pi t / T)\) for \(0 \leq t \leq T ;\) and \((b)\) a positive square-wave voltage, i.e., $$ V(t)=\left\\{\begin{array}{ll} V_{0} & 0 \leq t \leq \frac{T}{2} \\ 0 & \frac{T}{2} \leq t \leq T \end{array}\right. $$

Short Answer

Expert verified
The RMS voltage is \( \frac{V_0}{\sqrt{2}} \) for both sinusoidal and positive square-wave voltages.

Step by step solution

01

Understand the RMS Voltage Formula

The root mean square (RMS) voltage for a time-dependent voltage is given by the formula: \[ V_{\text{rms}} = \left[ \frac{1}{T} \int_{0}^{T} V^{2} dt \right]^{\frac{1}{2}}. \] Our task is to evaluate this expression for different forms of the voltage function \(V(t)\).
02

RMS Voltage for a Sinusoidal Voltage

For a sinusoidal voltage \( V(t) = V_0 \sin\left( \frac{2\pi t}{T} \right) \):1. Compute \(V(t)^2 = V_0^2 \sin^2\left( \frac{2\pi t}{T} \right)\).2. Integrate over the period \([0, T]\): \[ \int_0^T V_0^2 \sin^2\left( \frac{2\pi t}{T} \right) dt. \]3. Use the identity \( \sin^2(x) = \frac{1 - \cos(2x)}{2} \) to simplify the integral.4. Complete the integration to find: \[ \frac{1}{T} \int_0^T V_0^2 \left( \frac{1 - \cos\left( \frac{4\pi t}{T} \right)}{2} \right) dt = \frac{V_0^2}{2}. \]5. Take the square root to find: \[ V_{\text{rms}} = \frac{V_0}{\sqrt{2}}. \]
03

RMS Voltage for a Positive Square-Wave Voltage

For a positive square-wave voltage:1. Define the piecewise function: \[ V(t) = \begin{cases} V_0 & 0 \leq t < \frac{T}{2} \ 0 & \frac{T}{2} \leq t < T \end{cases}. \]2. Compute \(V(t)^2\) for each piece: - For \(0 \leq t < \frac{T}{2}, V(t)^2 = V_0^2\). - For \(\frac{T}{2} \leq t < T, V(t)^2 = 0\).3. Integrate each piece separately: - For \(0 \leq t < \frac{T}{2}, \int_0^{T/2} V_0^2 dt = \frac{V_0^2 T}{2}\). - For \(\frac{T}{2} \leq t < T, \int_{T/2}^T 0 \, dt = 0\).4. Sum the integrals and find the average over a period: \[ \frac{1}{T}\left( \frac{V_0^2 T}{2} + 0 \right) = \frac{V_0^2}{2}. \]5. Take the square root to find: \[ V_{\text{rms}} = \frac{V_0}{\sqrt{2}}. \]
04

Compile the Results

For both the sinusoidal and positive square-wave voltage forms, the RMS voltage is found to be:\[ V_{\text{rms}} = \frac{V_0}{\sqrt{2}}. \] This demonstrates that the RMS voltage in terms of the peak voltage \(V_0\) is the same for both types of periodic waveforms.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Sinusoidal Voltage
A sinusoidal voltage is a type of alternating current (AC) voltage that follows the shape of a sine wave over time. This wave-like pattern is fundamental in many electrical applications because it allows for the smooth and efficient transmission of energy. When you see something described as sinusoidal, it means it varies periodically in a smooth and predictable manner based on the sine function. In terms of voltage, this sinusoidal pattern can be mathematically expressed as:
\[ V(t) = V_0 \sin\left( \frac{2\pi t}{T} \right), \]
where \(V_0\) is the peak voltage and \(T\) is the period of the waveform. This equation tells us that the voltage magnitude oscillates between positive and negative peak values, creating a smooth and continuous wave.
- Sinusoidal voltages are prevalent in power systems, due to their ability to minimize energy loss.- They are also important in the design of circuits, such as oscillators and filters, which react to specific frequencies." into energy.
Square-Wave Voltage
Square-wave voltage is another form of AC voltage characterized by a waveform that switches abruptly between two levels, usually the maximum and zero, resulting in a shape that resembles a square. This waveform is used in digital electronics and pulse-width modulation applications. Unlike the gradual changes seen in sinusoidal waveforms, square-waves have sharp transitions.
A positive square-wave voltage can be represented mathematically as a piecewise function:
\[V(t) = \begin{cases} V_0 & 0 \leq t < \frac{T}{2} \ 0 & \frac{T}{2} \leq t < T \end{cases},\]
where \(V_0\) is the peak voltage, and \(T\) is the period of the waveform. This setup defines the two halves of the cycle:
  • During the first half of the period \((0 \leq t < \frac{T}{2})\), the voltage is at its peak,\(V_0\).
  • During the second half \((\frac{T}{2} \leq t < T)\), the voltage drops to zero.
Square-wave voltages are useful for their simplicity and the ease with which they can be generated and controlled, especially in applications requiring rapid switching, such as computer processors and signal processing circuits.
Integral Calculus
Integral calculus is a branch of calculus focusing on the concept of integration, which is essentially the process of finding the area under a curve. In the context of electrical engineering, it is crucial for deriving measurements such as the RMS voltage. The RMS (Root Mean Square) value is an important concept since it gives a consistent method for assessing the magnitude of a varying waveform.
To find the RMS voltage, integral calculus helps us evaluate the function\[ V_{\text{rms}} = \left[ \frac{1}{T} \int_{0}^{T} V^{2} dt \right]^{\frac{1}{2}}, \]
this expression enables us to compute the average power of an AC signal over one complete cycle. It involves squaring the voltage function, integrating over the period \(T\), and then taking the square root of the average.
  • The squaring of the voltage function ensures all values contribute positively to the average.
  • Integration calculates the area, which represents energy. This step is essential as it provides the accumulated total over a cycle.
  • Finally, taking the square root adjusts for the initial squaring, giving a meaningful average value.
Understanding and applying integral calculus allows us to simplify complex waveform analyses, making it an invaluable tool in electronics and electrical engineering.

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