An article analyzing direct current and alternating current

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An article analyzing direct current and alternating current

Posted Date: 2024-02-01

One of the main differences in the type of current in a circuit is whether the current is alternating current (alternating current) or direct current (direct current).

Both alternating current and direct current are widely used in electrical and electronic circuits, each serving different purposes.

Both AC and DC have their own characteristics and offer different advantages and can be used in different situations.

What is direct current, direct current

As the name suggests, DC is a form of electricity that flows in one direction—it's direct current, hence the name.

DC in basic circuits

The characteristics of direct current can be shown graphically. Here, it can be seen that the current is only positive or negative.

Diagram showing properties of direct current

Apply direct current, direct current

DC DC is used in many areas:

Batteries: Non-rechargeable and rechargeable batteries can only provide DC power. Rechargeable batteries also require direct current charging.

Electronic Devices: All devices like computers, radios, mobile phones, virtually all electronic devices use direct current to power electronic circuits. Bipolar transistors, FETs, and integrated circuits using these components all require DC to power them and will be damaged if reverse polarity is supplied. Although many of these items are powered by AC power, there is a unit inside the device called the power supply that converts the incoming AC power into DC power at the correct voltage.

Some electrical equipment: While many electrical equipment uses alternating current, some use direct current.

Solar Panels: Solar panels used to generate electricity generate DC electricity directly from the solar panel itself. When used with AC power to feed in power or to provide local AC power to an AC power source, a device called an inverter is required to convert the DC power from the solar panels to AC power.

What is alternating current, alternating current

Alternating current, alternating current is different from direct current. As the name suggests, it flows first in one direction and then in the other.

Diagram explaining alternating current

The image above shows the current waveform changing as a sine wave, with the current moving first in one direction and then in the other.

It's usually more common to see voltage changes. Likewise, with an alternating waveform, the voltage will change positive or negative.

It can be seen that for current and voltage, the waveform changes, in this case first positive and then negative.

AC sine wave waveform voltage

Sine waves are easy to present and understand, but a variety of other waveforms can also constitute AC waveforms with alternating current.

There are several key points to alternating waveforms. The first is the time period of the waveform. This is the time from a point on one cycle of the waveform to the same pint on the next cycle. Usually the peak is the easiest to see as shown in the diagram but it can take any point - for example when a specific voltage is reached in a given direction - this could be a voltage trigger point etc. The zero crossing is another easily identifiable point.

Another point about the alternating waveform is its frequency. This is the number of times a given point on the waveform is seen in one second, measured in hertz, hertz, where 1 hertz is one cycle per second. The example shown has a frequency of 3 Hz because three cycles are seen in one second.

As other examples, the frequency of the mains supply is 50 Hz or 60 Hz, depending on the country. Europe and many other countries use 50 Hz, while North America, the Caribbean, and some South American countries use 60 Hz.

AC applications

Alternating current is often used for power distribution. It has the advantage that it can be easily converted to other voltages using a simple transformer - transformers cannot work with DC.

If the power is distributed at high voltage, the losses are much lower. Consider, for example, a 250-volt power supply carrying 4 amps and 1 Ω line resistance. As power, watts = volts x amps, the power carried is 1000 watts. The power loss is I2x R = 16 Watts.

If a voltage line carries 4 amps, but the voltage is 250 000 volts, i.e. 250 kV, and the line carries 4 amps, then the power losses are still the same, but the losses in the entire transmission system carrying 1 MW and 16 watts are almost negligible.

It is for this reason that high voltages are used for power transmission and then reduced to relatively safe levels for use in homes and commercial properties.

Given that alternating current is used in power supply systems, it is also used in motors, heating, and many other projects without converting it to direct current.

AC and DC

In many areas, the decision can be made about AC vs. DC, and which form of power supply is best for a given application.

AC, AC, and DC, DC all have their advantages and disadvantages, but that means there are options to choose the best option for any given use or application. Alternating current, alternating current, is commonly used for power distribution, which is why the electrical sockets in our homes and at work provide alternating current to power whatever power is needed, but direct current, direct current, is more widely used in electronic boards themselves and in many other applications.

Both AC power supplies and DC power supplies are widely used in the electrical and electronic industries, and each has its own advantages.

Both alternating current and direct current are capable of providing power transmission, but with slightly different advantages.

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