CH 8: Alternating current

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What is the relationship between average power (Pave), RMS current (Irms), and RMS voltage (Vrms) in a purely resistive AC circuit?

Pave = Irms^2 / Vrms

Pave = Irms^2 * Vrms

Pave = Irms / Vrms

Pave = Irms * Vrms (correct)

What is the relationship between frequency (f) and period (T) in an AC circuit?

T = f^2

T = 1/f (correct)

T = 1/f^2

T = f

Which formula can be used to calculate the average power (Pave) in a resistive AC circuit, given the RMS current (Irms) and resistance (R)?

Pave = Irms * R

Pave = Irms / R

Pave = Irms^2 / R

Pave = Irms^2 * R (correct)

Why is AC preferred over DC for power transmission over long distances?

AC can be easily stepped up and down in voltage, reducing energy loss. Signup and view all the answers

Which of the following devices operates exclusively with AC?

Transformers Signup and view all the answers

Which of the following is NOT an advantage of alternating current (AC) over direct current (DC)?

AC is more efficient for long-distance power transmission due to lower voltage drop. Signup and view all the answers

In an AC circuit, the voltage and current vary over time in a sinusoidal pattern. At what points in the cycle do the maximum values (Vmax and Imax) occur?

At the peaks of the cycle Signup and view all the answers

What is the root mean square (RMS) voltage (Vrms) defined as?

The equivalent DC voltage that would produce the same amount of heat in a resistor as the AC voltage. Signup and view all the answers

In the context of AC circuits, what does the term 'transformability' refer to?

The ability to change the voltage level of the AC signal using transformers. Signup and view all the answers

Which of the following statements about the RMS current (Irms) is correct?

It is the equivalent DC current that would produce the same amount of heat in a resistor as the AC current. Signup and view all the answers

What does the period (T) of an AC signal represent?

Time taken to complete one cycle Signup and view all the answers

How does the frequency (f) of an AC signal relate to the number of cycles?

It is directly proportional to the number of cycles Signup and view all the answers

What is the role of transformers in AC circuits for power transmission?

Step up or down voltage Signup and view all the answers

How does average power calculation differ between DC and resistive AC circuits?

In AC, average power depends on resistance and RMS current Signup and view all the answers

Why is understanding RMS values important when dealing with AC circuits?

To analyze the sinusoidal variation Signup and view all the answers

Which parameter indicates the actual power used or dissipated in a purely resistive circuit?

$P_{ave}$ Signup and view all the answers

What is the standard frequency of AC power in South Africa?

50 Hz Signup and view all the answers

How does the utilization of RMS values aid in solving problems related to AC circuits?

To simplify calculations compared to DC circuits Signup and view all the answers

In an AC circuit, what is the phase relationship between the voltage and current waveforms?

The phase relationship depends on the circuit components Signup and view all the answers

What is the significance of using RMS values for AC voltage and current?

RMS values are used to compare the heating effects of AC with DC Signup and view all the answers

What is the relationship between the RMS voltage (Vrms) and the maximum voltage (Vmax) in an AC circuit?

Vrms = √2 * Vmax Signup and view all the answers

Why is AC preferred over DC for long-distance power transmission?

AC can be easily stepped up or down in voltage using transformers Signup and view all the answers

In an AC circuit, what is the period (T) defined as?

The time taken for one complete cycle of the waveform Signup and view all the answers

What is the primary reason for using high voltages in long-distance power transmission?

All of the above Signup and view all the answers

What is the relationship between the frequency (f) and the period (T) of an AC waveform?

f = 1/T Signup and view all the answers

In a purely resistive AC circuit, what is the phase relationship between the voltage and current waveforms?

The voltage and current are in phase Signup and view all the answers

What is the primary advantage of using AC in electric generators and motors?

AC allows for easy changing of magnetic fields Signup and view all the answers

What is the significance of using high voltages in AC power transmission?

Reduces current needed for the same power transfer Signup and view all the answers

Why is it easier to convert AC to DC compared to converting DC to AC?

AC involves changing magnetic fields Signup and view all the answers

What is the main advantage of using transformers in AC circuits?

Step up or down voltage levels Signup and view all the answers

Which statement best describes Root Mean Square (RMS) values in AC circuits?

They allow comparison to constant DC values Signup and view all the answers

What do Vmax and Imax represent in an AC circuit?

Peak voltage and current values Signup and view all the answers

In which scenario would thinner wires be used for power transmission?

High-voltage AC transmission Signup and view all the answers

How do RMS Current (Irms) and RMS Voltage (Vrms) simplify analysis in AC circuits?

By facilitating comparisons with DC circuits Signup and view all the answers

What happens to voltage and current values at every half cycle of an AC waveform?

Both values are zero Signup and view all the answers

Which statement best explains why high-voltage AC transmission reduces energy loss?

Reduced current leads to lower heating losses in power lines. Signup and view all the answers

Which of the following formulas can be used to calculate the average power ($P_{ave}$) in a purely resistive AC circuit, given the RMS current ($I_{rms}$) and resistance ($R$)?

$P_{ave} = I_{rms}^2 R$ Signup and view all the answers

What is the relationship between the frequency ($f$) and the period ($T$) of an AC waveform?

$f = 1 / T$ Signup and view all the answers

Why is AC preferred over DC for long-distance power transmission?

AC can be easily stepped up and down in voltage, reducing energy loss. Signup and view all the answers

What is the significance of using RMS values for AC voltage and current?

RMS values allow for direct comparison to DC values. Signup and view all the answers

In an AC circuit, what is the phase relationship between the voltage and current waveforms for a purely resistive load?

The voltage and current are in phase. Signup and view all the answers

What is the primary advantage of using AC in electric generators and motors?

AC can be easily transformed to different voltage levels. Signup and view all the answers

In the context of AC circuits, what does the term 'transformability' refer to?

The ability to change the voltage and current levels of an AC signal. Signup and view all the answers

What is the relationship between the RMS voltage ($V_{rms}$) and the maximum voltage ($V_{max}$) in an AC circuit?

$V_{rms} = \sqrt{2} V_{max}$ Signup and view all the answers

What is the standard frequency of AC power in South Africa?

50 Hz Signup and view all the answers

CH 8: Alternating current

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Questions and Answers

What is the relationship between average power (Pave), RMS current (Irms), and RMS voltage (Vrms) in a purely resistive AC circuit?

What is the relationship between frequency (f) and period (T) in an AC circuit?

Which formula can be used to calculate the average power (Pave) in a resistive AC circuit, given the RMS current (Irms) and resistance (R)?

Why is AC preferred over DC for power transmission over long distances?

Which of the following devices operates exclusively with AC?

Which of the following is NOT an advantage of alternating current (AC) over direct current (DC)?

In an AC circuit, the voltage and current vary over time in a sinusoidal pattern. At what points in the cycle do the maximum values (Vmax and Imax) occur?

What is the root mean square (RMS) voltage (Vrms) defined as?

In the context of AC circuits, what does the term 'transformability' refer to?

Which of the following statements about the RMS current (Irms) is correct?

What does the period (T) of an AC signal represent?

How does the frequency (f) of an AC signal relate to the number of cycles?

What is the role of transformers in AC circuits for power transmission?

How does average power calculation differ between DC and resistive AC circuits?

Why is understanding RMS values important when dealing with AC circuits?

Which parameter indicates the actual power used or dissipated in a purely resistive circuit?

What is the standard frequency of AC power in South Africa?

How does the utilization of RMS values aid in solving problems related to AC circuits?

In an AC circuit, what is the phase relationship between the voltage and current waveforms?

What is the significance of using RMS values for AC voltage and current?

What is the relationship between the RMS voltage (Vrms) and the maximum voltage (Vmax) in an AC circuit?

Why is AC preferred over DC for long-distance power transmission?

In an AC circuit, what is the period (T) defined as?

What is the primary reason for using high voltages in long-distance power transmission?

What is the relationship between the frequency (f) and the period (T) of an AC waveform?

In a purely resistive AC circuit, what is the phase relationship between the voltage and current waveforms?

What is the primary advantage of using AC in electric generators and motors?

What is the significance of using high voltages in AC power transmission?

Why is it easier to convert AC to DC compared to converting DC to AC?

What is the main advantage of using transformers in AC circuits?

Which statement best describes Root Mean Square (RMS) values in AC circuits?

What do Vmax and Imax represent in an AC circuit?

In which scenario would thinner wires be used for power transmission?

How do RMS Current (Irms) and RMS Voltage (Vrms) simplify analysis in AC circuits?

What happens to voltage and current values at every half cycle of an AC waveform?

Which statement best explains why high-voltage AC transmission reduces energy loss?

Which of the following formulas can be used to calculate the average power ($P_{ave}$) in a purely resistive AC circuit, given the RMS current ($I_{rms}$) and resistance ($R$)?

What is the relationship between the frequency ($f$) and the period ($T$) of an AC waveform?

Why is AC preferred over DC for long-distance power transmission?

What is the significance of using RMS values for AC voltage and current?

In an AC circuit, what is the phase relationship between the voltage and current waveforms for a purely resistive load?

What is the primary advantage of using AC in electric generators and motors?

In the context of AC circuits, what does the term 'transformability' refer to?

What is the relationship between the RMS voltage ($V_{rms}$) and the maximum voltage ($V_{max}$) in an AC circuit?

What is the standard frequency of AC power in South Africa?

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