Khái Niệm Cơ Bản Về Mạch AC

Front

What is the typical unit of frequency in AC circuits?

Back

Hertz

Answer explanation

The typical unit of frequency in AC circuits is Hertz (Hz), which measures cycles per second. Other options like Newton, Ohm, and Watt refer to force, resistance, and power, respectively, and are not units of frequency.

Front

RMS in AC analysis

Back

Root mean square value

Answer explanation

RMS stands for Root Mean Square value, which is a statistical measure used in AC analysis to determine the effective value of an alternating current or voltage. It is not the actual average or resistance average.

Front

The frequency of household AC in most countries is:

Back

50/60 Hz

Answer explanation

The standard frequency for household AC power in most countries is either 50 Hz or 60 Hz, depending on the region. This is essential for the proper functioning of electrical appliances.

Front

Which waveform is commonly used in AC electrical systems?

Back

Sine wave

Answer explanation

The sine wave is the most common waveform in AC electrical systems due to its smooth periodic oscillation, which allows for efficient energy transfer and is fundamental in alternating current applications.

Front

In an AC circuit with pure resistance, the current and voltage are:

Back

In phase

Answer explanation

In an AC circuit with pure resistance, the current and voltage are in phase, meaning they reach their maximum and minimum values simultaneously. This is why the correct answer is 'In phase'.

Front

The peak value of a sine wave is 10V. What is its RMS value?

Back

7.07V

Answer explanation

The RMS value of a sine wave is calculated as peak value divided by √2. For a peak value of 10V, RMS = 10V / √2 ≈ 7.07V. Thus, the correct answer is 7.07V.

Front

If the RMS voltage is 100V, what is the peak voltage approximately?

Back

141.4V

Answer explanation

The peak voltage (V_peak) can be calculated from the RMS voltage (V_rms) using the formula V_peak = V_rms × √2. For 100V RMS, V_peak = 100V × 1.414 ≈ 141.4V, making 141.4V the correct answer.

Front

The average value of a fully rectified sine wave is:

Back

2Vpeakπ​​

Answer explanation

The average value of a fully rectified sine wave is calculated as 2Vpeak/π. This is derived from integrating the absolute value of the sine wave over one period and normalizing it, confirming that the correct answer is 2Vpeak/π.

Front

Which form is NOT a representation of AC voltage? Options: Instantaneous, RMS, Peak-to-peak, Constant

Back

Constant

Answer explanation

The constant form does not represent AC voltage, as it implies a steady value, while AC voltage varies over time. Instantaneous, RMS, and peak-to-peak are all valid representations of AC voltage.

Front

The time period of a 50 Hz AC signal is:

Back

0.02 s

Answer explanation

The time period (T) is the inverse of frequency (f). For a 50 Hz signal, T = 1/f = 1/50 = 0.02 s. Thus, the correct answer is 0.02 s.