Chapter 1: Problem 13
The current through a particular circuit element is given by \(i(t)=10 \sin (200 m t) A\) in which \(t\) is in seconds and the angle is in radians. a. Sketch \(i(t)\) to scale versus time for \(t\) ranging from 0 to \(15 \mathrm{ms}\) b. Determine the net charge that passes through the element between \(t=0\) and \(t=10 \mathrm{ms}\), c. Repeat for the interval from \(t=0\) to \(t=15 \mathrm{ms}\).
Short Answer
Step by step solution
Understanding the Problem Statement
Sketching the Current over Time
Calculating Charge from 0 to 10ms
Calculating Charge from 0 to 15ms
Conclusion
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Waveform Sketching
- Amplitude: The amplitude of the sinusoidal function here is 10 A. This means the wave oscillates between +10 A and -10 A.
- Period: The period \(T\) is the time it takes for the wave to complete one full cycle. It is calculated as \( T = \frac{1}{f} \), where \( f \) is the frequency. For this function, the frequency is determined by \( \frac{200 \pi}{2 \pi} = 100 \) Hz, so the period \(T\) is 0.01 seconds or 10 milliseconds.
- Sketching: You start at 0 ms with \(i(t) = 0\), climb to 10 A at 2.5 ms, return to 0 A at 5 ms, fall to -10 A at 7.5 ms, and return to 0 at 10 ms, completing one full cycle. From 10 ms to 15 ms, it repeats starting again from 0 A, representing half a cycle.
Charge Calculation
- Charge Formula: The charge \(Q\) is defined by the integral \( Q = \int_{t_1}^{t_2} i(t) \, dt \). This represents the area under the current-time graph between two times \(t_1\) and \(t_2\).
- Calculation from 0 to 10ms: For time \(t = 0\) to \(t = 10 \mathrm{ms}\), the wave completes exactly one period. Since the sinusoidal wave is symmetrical, the areas above and below the time axis are equal, canceling each other out, resulting in a net charge of 0 C.
- Calculation from 0 to 15ms: For \(t = 0\) to \(t = 15 \mathrm{ms}\), one and a half cycles are considered. Over the additional half cycle (from 10ms to 15ms), there is a net positive area under the curve, resulting in a calculated charge of approximately 0.0318 C.
Integral of Sinusoidal Function
- Integration Process: The integral \( \int 10 \sin(200 \pi t) \, dt \) yields \(-\frac{10}{200 \pi} \cos(200 \pi t) + C\), where \(C\) is the constant of integration. It turns the sinusoidal function into one involving cosine.
- Boundary Evaluation: For a fixed interval, evaluate the antiderivative at the upper and lower bounds and subtract: \[ Q = \left[-\frac{10}{200 \pi} \cos(200 \pi \times t_2) + C\right] - \left[-\frac{10}{200 \pi} \cos(200 \pi \times t_1) + C\right] \].
- Specific Intervals: Applying this to both 0 to 10 ms and 0 to 15 ms gives precise values reflecting the net charge — 0 C and 0.0318 C, respectively, highlighting symmetry and area concepts when interpreting sinusoidal functions over their cycles.