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Difference between AC and DC Circuits

Alternating Current:
In alternating current the flow of electric charges reverses after a certain period. The period in which the current reverses can also be known as frequency of the current. This is mostly produced by generators where the polarity of the bushes reverses after certain period and hence the flow of the electrons also reverses.

Direct Current:
In direct current, the flow of electrons or electric charges does not reverses that is it remains in the same direction. The direct current is very stable however it is more dangerous than the AC. The DC is also produced by generator however the AC generated by the generator is smartly converted to the DC. In DC generators the bushes changes the polarity and also the circuitry which takes the charges from the bushes. This way the current always flows in one direction. The DC is also generated mostly from the batteries.

DC Circuits and AC circuits:
In DC circuits the voltage source is constant and hence a constant current flows through the circuit. Due to this fact the DC circuits has pure resistances.

To calculate current in DC circuits we require simple equation like:

I = $\frac{V}{R}$;

The voltage in the DC circuit is given by V and resistance is given by R and since both are constant so the DC is constant and is proportional to voltage V.

In AC circuits, the voltage source produces electric current with a certain frequency and hence the circuit is not pure resistive in nature, the circuit offers resistive as well as reactive impedance.  The impedance is the combination of resistance, inductance and capacitance.

To calculate current in AC circuits we require equation like;

I = $\frac{V}{(Impedance)}$;

Since in AC circuits the voltage source is not constant and hence the current is also not constant and varies in proportional to that of the voltage.

The voltage in the AC circuit is given by;

V = V0 sin wt;

Impedance = XR + XL + XC;

We can understand the difference between AC and DC circuits by example.

Ex. Find the current if the voltage source of 15 volts is connected to a resistance of 5 ohms?

Ans. From the question it is clear that the voltage source is constant and hence the current produced would be DC. Since V = 15 volts and R = 5 ohms so the current would be;

I = $\frac{15}{5}$;

I = 3 amperes.

Ex. Find the current if the voltage source of 15 volts with a frequency of 50 hertz is connected to a circuit which has an impedance of 5?

Ans. As from the question it is clear that the voltage source is not constant is varying with the frequency of 50 hz, so the current produced is also proportional to that of the voltage and is also varying. Now using the above equation we can write the AC as;

I = $\frac{15\sin (100\pi t)}{5}$

I = 3 sin(100 πt);

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From Yahoo Answers

Question:So I had this EXACT question and been searching google for an answer which lead me to a question site with the same question, but with my luck noone had answered. So I just decided to copy and paste it here. "what is difference between DC current breaker and Ac current Breaker? Can I use the AC current breaker 380V in 24DC-voltage for the same current rating?" SOMEONE KNOW THE ANSWER, PLEASE! :P

Answers:AC alternates - so the current naturally passes through zero twice very cycle. Interruption in an AC circuit breaker takes place at one of those natural current zeros. There is arcing during the course of interruption - dielectric strength builds up gradually as the breaker contacts physically open, and until the contacts have opened sufficiently, conduction will re-establish after the initial currents zeros. But once the contacts are open sufficiently to provide enough dielectric strength, the arc will be extinguished. The breaker mechanism may include provides to accelerate arc extinction - typical scheme include arrangements that extend and cool the arc. DC does not alternate, so there are no natural current zeros. That implies two things. First, the physical opening of the breaker must be faster and physically greater to create sufficient dielectric withstand to extinguish the arc. That is usually what is done with smaller breaker. But for breakers with larger electrical ratings, it may be necessary to include a provision to force an artificial current zero. One approach is to include a capacitor that is charged by the normal DC voltage, and that is inserted into the circuit as the breaker opens to oppose the normal voltage to force the current to zero.

Question:

Answers:The source of energy. In a DC circuit, the source of energy provides a constant voltage to the circuit. In an AC circuit, the source of energy provides a varying voltage to the circuit, usually varying sinusoidally with time, causing an alternating current in a pure resistive load.

Question:

Answers:Alternating current (ac) reverses the flow of electrons 60 times per second and can be used in transformers to increase or reduce voltage. Most homes have single phase current (110 volts) for lights, radios, microwave ovens, etc.) and two phase current (220 volts) for electric stoves, central air conditioning, and clothes dryers, etc.). Direct current (dc) is usually obtained in the home using batteries at about 1.5 volts per cell, but can be placed in series (as in a flashlight) to add cell voltages. Most vehicles us 12 volt batteries. Because the voltage of batteries is generally much less than ac sources it is much safer if accidentally touched. However, high dc voltages of perhaps 110 volts would be more dangerous than 110 volt ac because dc current tenses muscles in one direction and if a dc wire is grabbed it may not be possible to let go. Many dc batteries use heavy metals (cadmium, etc.) that are highly toxic and must be disposed of correctly. In some jurisdictions retailers who sell toxic batteries must also accept them for proper disposal to prevent contamination of groundwater flowing away from dumps.

Question:So in an RC circuit, you can have DC or AC currents?

Answers:RC - Roman Catholics AC - Anglo Catholics DC - Doomsday Catholics They are not compatible with each other and they will blow up if you join these circuits together. Most explosive is the DC

From Youtube

Capacitors in AC and DC Circuits :Capacitors in AC and DC CircuitsThe simplest capacitor consists of two metal plates located at a certain distance in parallel to each other. The space between the capacitor's plates can be filled with air or solid dielectric. The larger the area of such plates and the smaller the distance between them, the bigger is the electric capacitance of the capacitor.If the capacitor plates are connected to the DC power supply, the charges of such power supply will move to the capacitor, and the capacitor charging current will start flowing in the circuit. As the capacitor charge increases, the voltage on it will also grow, and the voltage difference between the capacitor and the power supply will begin to decrease. This will also lead to a decrease in the charging current. When the voltage on the capacitor reaches that of the ideal voltage source, the voltage difference between the power supply and the capacitor will be equal to zero, and, therefore, there will be no charging current any more.In other words, accumulation of charge on the capacitor is accompanied by an increase in its resistance to electric current. The capacitor charged from the power supply voltage acts as an infinitely large resistor in the DC circuit, and, as a result, such circuit breaks.On the other hand, if we connect the capacitor to an AC power supply, the capacitor will be conducting AC current, which is a charging and discharging current of the capacitor. That's why the capacitor in the AC current can be ...