Gibilisco - Alternating-current Basics

The length of time between a point in one cycle and the same point in the next cycle of an AC wave is referred to as the period. It represents the time taken for the wave to complete one full cycle. The frequency, on the other hand, refers to the number of cycles that occur in a given time period. Magnitude relates to the size or amplitude of the wave, while polarity indicates the direction or orientation of the wave.

A degree of phase represents 1/360 of a cycle. In a cycle, there are 360 degrees. This means that each degree represents 1/360th of the total cycle. Therefore, the correct answer is 1/360 of a cycle.

AC (alternating current) is easier to transform from one voltage to another compared to DC (direct current). This is because AC voltage can be easily stepped up or stepped down using transformers. Transformers work based on the principle of electromagnetic induction, which is more efficient for AC than DC. On the other hand, transforming DC voltage requires the use of more complex and less efficient methods such as choppers or inverters. Therefore, the ability to easily transform AC voltage makes it advantageous in utility applications.

The period of an AC wave is the time it takes for one complete cycle of the wave to occur. The frequency of an AC wave is the number of cycles that occur in one second. Since the period represents the time for one cycle and the frequency represents the number of cycles in one second, they are inversely related. Therefore, the period of an AC wave is equal to 1 divided by the frequency in hertz.

In a perfect sine wave, the peak-to-peak amplitude is equal to twice the peak amplitude. This means that the distance between the highest point (peak) and the lowest point (trough) of the wave is twice the height of the peak. It is important to note that the peak-to-peak amplitude is a measure of the total variation of the wave, while the peak amplitude refers to the maximum value of the wave.

Frequency is the correct answer because it refers to the number of cycles or oscillations per second in an alternating current (AC) waveform. In AC, the direction of current flow constantly changes, causing the frequency to vary. However, in direct current (DC), the current flows in only one direction, so the frequency remains constant at zero. Therefore, frequency can vary with AC but never with DC.

The correct answer is that three-phase AC consists of three sine waves in different phases. In three-phase AC, there are three separate waveforms that are 120 degrees out of phase with each other. These waveforms are typically represented as sine waves and are used in power distribution systems to provide a more efficient and balanced power supply. Each waveform carries the same frequency but has a different phase relationship, resulting in a more stable and reliable power transmission.

The type of natural energy source used does not affect the power output available from a particular ac generator. The power output of an ac generator is determined by factors such as the strength of the magnet, the number of turns in the coil, and the speed of rotation of the coil or magnet. The type of natural energy source used, such as wind, water, or fossil fuels, may determine the initial source of energy to rotate the coil or magnet, but it does not directly impact the power output once the generator is in operation.

When two perfect sine waves have the same frequency and the same amplitude, but are in opposite phase, they will interfere destructively. This means that the positive peaks of one wave will coincide with the negative peaks of the other wave, resulting in cancellation. As a result, the composite wave will have zero amplitude, meaning it does not exist.

The phase difference between two waves is determined by the fraction of a cycle that they differ by. In this case, the waves differ by exactly 1/20 of a cycle. To convert this fraction into degrees, we multiply it by 360 (since a full cycle is 360°). Therefore, 1/20 * 360 = 18°. Hence, the phase difference between these two waves is 18°.

The positive peak voltage in a utility circuit is equal to the peak value of the voltage waveform, which is √2 times the rms value. In this case, the rms voltage is 117 V, so the positive peak voltage can be calculated as √2 * 117 V ≈ 165 V. Therefore, the correct answer is +165 V.

The frequency of an ac wave is determined by the number of cycles it completes in one second. The period of the wave is given as 1.000 millisecond (1.000 ms), which means it completes 1 cycle in 1 ms. The sixth harmonic of the wave would complete 6 cycles in the same time period. To find the frequency, we divide the number of cycles (6) by the time period (1 ms), which gives us a frequency of 6 kHz.

The angular frequency of an AC signal is equal to 2π times the frequency. In this case, the given frequency is 1770 Hz. Therefore, the angular frequency can be calculated by multiplying 1770 by 2π, which gives us 11,120 rad/s.

A triangular wave exhibits a defined rise and a defined decay, and the two are equal. This means that the waveform increases from its lowest point to its highest point in a defined manner, and then decreases from its highest point back to its lowest point in the same defined manner. The rise and decay are symmetrical, resulting in equal durations for both phases of the waveform.

An ac signal with only one frequency component appears as a single pip on a spectrum analyzer. This is because a spectrum analyzer displays the frequency content of a signal, and when there is only one frequency component, it will be represented as a single point or pip on the display. The other options, such as a sine wave, square wave, or sawtooth wave, would show multiple frequency components, resulting in a different waveform representation on the spectrum analyzer.

When two perfect sine waves with the same frequency and phase are combined, they constructively interfere, resulting in a composite wave. The amplitude of the composite wave is determined by adding the amplitudes of the two original waves together. Therefore, the correct answer is that the composite wave is a sine wave with an amplitude equal to the sum of the amplitudes of the two original waves.

If a 175-V dc source were connected in series with the utility mains from a standard wall outlet, the result would be fluctuating dc. This is because the utility mains provide alternating current (ac), which constantly changes direction. When the dc source is connected in series, it would cause the current to fluctuate between the dc voltage and the ac voltage from the mains. As a result, the output would be a fluctuating direct current (dc), with the voltage constantly changing between the dc source voltage and the ac voltage from the mains.

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