What is the difference between dc and ac current

The Ac current can be produced with a device named alternator that produces the alternating current. Suppose a piston is inserted inside a pipe and connected with a rotating rod as in the pin pic below. Here the piston has two strokes one towards upward and the other towards backward on the upward stroke, the water moves in a clockwise direction and the backward direction the water displaces in an anticlockwise direction so in this way water direction changes its direction periodically with oscillation of the piston.

Every Ac Waveforms have a divider line or called the zero voltage line that divides the waveform two halves as the Ac current changes the magnitude and direction periodically so on every one complete cycle it reaches zero volts. The total amount of time taken by a waveform to repeat itself or to repeat its one cycle is called time period. You can also say the total amount of time taken by wave form to complete its one complete cycle is called time period. The rate at which the waveform repeats itself is called frequency or you can say the the number of times the waveform repeats in one second is called frequency.

The DC current is a unidirectional flow of current or electric charge unlike AC it does not change the magnitude and polarity with time. The DC current has constant magnitude and direction and as the direction and magnitude not changes so the frequency of DC current is zero.

The electrons in DC current flow from high electron density to low electron density. We can get DC from Ac current using the process called rectification and the device that does this is called a rectifier. Not all electrical devices use DC power, though. Many devices, household appliances, especially, such as lamps, washing machines, and refrigerators, all use AC power, which is delivered directly from the power grid via power outlets.

Although many of today's electronics and electrical devices prefer DC power because of its smooth flow and even voltage, we could not get by without AC. Both types of power are essential; one is not "better" than the other. In fact, AC dominates the electricity market; all power outlets bring power into buildings in the form of AC, even where the current may need to be immediately converted into DC power. This is because DC is not capable of traveling the same long distances from power plants to buildings that AC is.

It is also a lot easier to generate AC than DC due to the way generators turn, and the system is on the whole cheaper to operate—with AC, power can be hauled through national grids via miles and miles of wire and pylons easily. DC primarily comes into play, where a device needs to store power in batteries for future use. Smartphones, laptops, portable generators, torches, outdoor CCTV camera systems… you name it, anything battery-powered relies on storing DC power.

In DC, the electrons flow steadily in a single direction, or "forward. A magnetic field near a wire causes electrons to flow in a single direction along the wire, because they are repelled by the negative side of a magnet and attracted toward the positive side.

This is how DC power from a battery was born, primarily attributed to Thomas Edison's work. AC generators gradually replaced Edison's DC battery system because AC is safer to transfer over the longer city distances and can provide more power.

Instead of applying the magnetism along the wire steadily, scientist Nikola Tesla used a rotating magnet. When the magnet was oriented in one direction, the electrons flowed towards the positive, but when the magnet's orientation was flipped, the electrons turned as well.

Another difference between AC and DC involves the amount of energy it can carry. Each battery is designed to produce only one voltage, and that voltage of DC cannot travel very far until it begins to lose energy. But AC's voltage from a generator, in a power plant, can be bumped up or down in strength by another mechanism called a transformer.

Transformers are located on the electrical pole on the street, not at the power plant. They change very high voltage into a lower voltage appropriate for your home appliances, like lamps and refrigerators. AC can even be changed to DC by an adapter that you might use to power the battery on your laptop.

Here is a short animation showing this principle:. Generating AC can be compared to our previous water analogy :. To generate AC in a set of water pipes, we connect a mechanical crank to a piston that moves water in the pipes back and forth our "alternating" current. Notice that the pinched section of pipe still provides resistance to the flow of water regardless of the direction of flow.

AC can come in a number of forms, as long as the voltage and current are alternating. If we hook up an oscilloscope to a circuit with AC and plot its voltage over time, we might see a number of different waveforms.

The most common type of AC is the sine wave. The AC in most homes and offices have an oscillating voltage that produces a sine wave. Triangle waves are found in sound synthesis and are useful for testing linear electronics like amplifiers. We often want to describe an AC waveform in mathematical terms. For this example, we will use the common sine wave.

There are three parts to a sine wave: amplitude, frequency, and phase. V t is our voltage as a function of time, which means that our voltage changes as time changes. The equation to the right of the equals sign describes how the voltage changes over time. V P is the amplitude. The sin function indicates that our voltage will be in the form of a periodic sine wave, which is a smooth oscillation around 0V. This is given in the form of hertz or units per second. The frequency tells how many times a particular wave form in this case, one cycle of our sine wave - a rise and a fall occurs within one second.

As time varies, our waveform varies. Phase is a measure of how shifted the waveform is with respect to time. It is often given as a number between 0 and and measured in degrees.

We can turn to our trusty outlet for a good example of how an AC waveform works. In the United States, the power provided to our homes is AC with about V zero-to-peak amplitude and 60Hz frequency. We can plug these numbers into our formula to get the equation remember that we are assuming our phase is 0 :. We can use our handy graphing calculator to graph this equation. If no graphing calculator is available we can use a free online graphing program like Desmos Note that you might have to use 'y' instead of 'v' in the equation to see the graph.

Notice that, as we predicted, the voltage rise up to V and down to V periodically. Additionally, 60 cycles of the sine wave occurs every second. If we were to measure the voltage in our outlets with an oscilloscope, this is what we would see WARNING: do not attempt to measure the voltage in an outlet with an oscilloscope! This will likely damage the equipment. This is also correct. When talking about AC since the voltage changes constantly , it is often easier to use an average or mean.

To accomplish that, we use a method called "Root mean squared.