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What is the Difference Between AC and DC Current?

By S. Mithra
Updated May 17, 2024
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Electricity is a type of energy that involves the movement of electrons along a conductor, such as a wire. The flow of electrons can occur in one direction or both directions along the wire. When electricity flows in one direction, it is referred to as direct current (DC). Alternating current (AC) is when the electrons flow in both directions — one and then the other. Batteries produce direct current, and electrical power grids that provide electricity to homes and other buildings use alternating current.

Direct Current

In nature, electricity occurs only rarely, in some animals or with lightning. In the search to create electrical energy, scientists discovered that electrical and magnetic fields are related. A magnetic field near a wire causes electrons to flow in a single direction along the wire because they are repelled and attracted by the poles of the magnet. This is how DC power from a battery was born, a development that is primarily attributed to American inventor Thomas Edison's work and promotion during the 19th century.

Alternating Current

In the late 19th century, another scientist, Serbian-American engineer Nikola Tesla, worked on developing AC because could transfer different amounts of power. Instead of applying the magnetism along the wire steadily, he used a magnet that was rotating. When the magnet was oriented in one direction, the electrons flowed toward 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 that each one can carry. Every battery is designed to produce only one voltage level, and that voltage of direct current cannot travel very far until it begins to lose energy. AC voltage from a generator in a power plant can be bumped up or down in strength by another mechanism, called a transformer.


Transformers are used wherever an electrical voltage needs to be increased or decreased. For example, they are commonly seen on electrical poles. A power plants produces electricity at a very high voltage so that it can travel great distances. The voltage must be reduced, however, before the electricity reaches homes and other buildings that use it to power appliances, machinery and other devices. AC also can be changed to DC by an adapter, such as the kind used to power the battery on a laptop computer.

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Discussion Comments
By sibanisankar — On Jan 15, 2015

Which has more heat effect (dc or ac)?

By fahdshihab — On Feb 07, 2014

How we can use the electrical current to overcome the magnetic field on a pipe when we want to weld?

By anon278193 — On Jul 04, 2012

How does DC current lose its energy?

By anon259617 — On Apr 07, 2012

What is the difference between voltage and power?

By anon259538 — On Apr 06, 2012

What happens if you chop the ground rod off that is located outside the house and that is buried approximately six feet down?

By anon245504 — On Feb 05, 2012

DC current is more dangerous because it doesn't pulse like AC. If it gets you, it will hold you till you fry.

By anon240536 — On Jan 14, 2012

Are electrical blankets harmful to humans?

By cdulnik — On Jul 04, 2011

Ac is the best way to utilize electricity.

Nikola Tesla is the man behind AC and all the devices that improve our lives. Check out Nikola Tesla the Forgotten Wizard online.

Tom Edison was a type of inventor who had no idea what electricity is. He would steal others ideas and claim they were his.

The main difference between AC and DC is AC sets up a type of "radiation within the wire" and the work is done at the point of contact, whereas DC must travel the full distance from the source to the load and back to the source.

By anon178282 — On May 20, 2011

what is the different between 100 mA using 14 VDC and 100 mA using 120 VAC?

By anon167560 — On Apr 13, 2011

which is more dangerous, DC or AC, and why?

By anon163529 — On Mar 28, 2011

DC loses more energy when traveling further due to what happens when applying the magnetism along the wire steadily and not using the magnet that is rotating. When the magnet is oriented in one direction, will the electrons flow towards the positive, but when the magnet's orientation is flipped, did the electrons turn as well?

By anon153322 — On Feb 17, 2011

why is the electricity power supply in AC form but not in DC form?

By anon152318 — On Feb 13, 2011

Why can't direct current be transformed?

By anon149150 — On Feb 03, 2011

What is the difference between an AC and a DC generator? Is it really the commutator and the split rings?

By anon146846 — On Jan 27, 2011

how does a battery produce a DC current? i really want to know. please tell me.

By anon133951 — On Dec 13, 2010

can anyone tell me how many hertz it takes to crack water molecule. specific if possible and can it be done with both AC or DC or only one.

By prabhatkumar — On Nov 17, 2010

what is the phase difference in electronics?

By anon127709 — On Nov 17, 2010

what is a rectifier.

By anon123226 — On Oct 31, 2010

If I want to check the voltage coming out of a battery charger with a volt meter, do I check AC or DC volts?

By anon119412 — On Oct 18, 2010

Which is more dangerous, ac or dc?

By anon112844 — On Sep 22, 2010

Actually, DC is a much better way to transfer high power over long distances. It requires a high voltage with reduced current, just like AC does, but the losses are much less than with AC. The reason that AC was initially used was because the change from high voltage DC to AC was very difficult to do reliably, and really wasn't feasible until the 1960's. Search this with Google and you'll find out more than you will on this forum. Search: High voltage direct current supergrids. It is an amazing article and very informative.

By anon108720 — On Sep 04, 2010

why is energy loss in DC more than that of AC during transmission ?

By anon103296 — On Aug 11, 2010

an advantage ac voltage has over dc voltage is that in a motor it does not require carbon brushes or commutators to contact the shaft as it rotates.

this is an advantage because the contact creates both heat and sparks, especially at high speeds, which could cause problems if the motor is situated in an environment near flammable or explosive vapours. hope this can help.

By anon102278 — On Aug 07, 2010

In general taking a step forward and a step backward implies that we are in the same position. i mean at the same place, you said that in AC the electrons move backward and forward, hence there will be no movement of electrons, but moving of electrons through a conductor causes electricity. Then how can you argue that it causes electricity?

By anon92673 — On Jun 29, 2010

The article says, "Transformers are located on the electrical pole on the street, not at the power plant." That is incorrect! There are transformers at the power plant that step the voltage up from what the generator produces, unless the generator happens to produce the correct voltage.

The voltage has to travel over transmission lines, because the energy losses due to heat are lower when current is lowered. By stepping up voltage in a transformer simultaneously steps down the current. Once the electricity nears an area where it is to be consumed, the voltage is stepped down and the increased losses due to heat are offset by the reduced cost of the numerous wires in a residential area being rated for a lower voltage.

By anon92567 — On Jun 29, 2010

why do we use ac in our wall outlets? why not dc?

By anon88268 — On Jun 03, 2010

If an AC voltage has a frequency of 60 HZ, what is its period?

By anon87881 — On Jun 02, 2010

In power electronics how is converting power ac to dc (rectifier) and dc to ac power(inverter) used and given motor(load)?

By anon83685 — On May 12, 2010

I want the brief explanation and the use of the flux inside the soldering iron and its nature.

By anon83567 — On May 11, 2010

I am doing a debate in my science class over whether ac or dc is better. i am doing the dc side. any ideas for what will help me win? please post back.

By anon80141 — On Apr 26, 2010

I am an artist who knows very little about electricity. I am wiring 30 clock mechanisms together. They each take 1 AA battery.

I was planning on wiring ten together and using a 15v 1.5A dc plug- however, it seems the 1.5 was not enough and I would need a 2.5A. I can't seem to find this type of plug anywhere on the internet.

Any suggestions to help me wire this would be a huge help! Thank you!

By anon72171 — On Mar 22, 2010

Briefly explain five differences between AC and DC.

By anon70800 — On Mar 16, 2010

what are the important key concepts to focus on the power supplies chapter?

By anon67626 — On Feb 25, 2010

is there any downside/danger to hooking up DC power to an AC motor such as the one in a drill or saw?

By anon61059 — On Jan 18, 2010

33.voltage is low in dc

By anon58016 — On Dec 29, 2009

Regarding the safety measurements

First: You have to have very good voltmeter probes, what i mean is very good quality.

Second: Be careful about the attaching the probes you have and hold them from the insulation side

Third: Be very very careful with measuring the high voltages

Fourth: Don't trust any electrical device even it's turned off.

Fifth: The basic rule, what i am calling the golden rule is that "You are the one that if some thing happens will get harmed" so you have to create rules before you do anything.

i hope what i know about safety measurements will give a brief an idea about this subject.

thank you. eng.mostafa from iraq

By anon56755 — On Dec 17, 2009

if we take an a.c component, why we find only volt-frequency characteristics and v-i characteristics, why don't we measure current vs frequency?

By anon54517 — On Nov 30, 2009

to anon44613: you measure voltage in parallel because you are measuring the voltage across whatever it is you are measuring. you break the circuit and insert the ammeter in series because to measure current you measure the flow of electrons through the circuit.

By anon52561 — On Nov 15, 2009

I have a welding machine 220/440 Dc 3phase. Can i hook to 220/440ac 1phase if a transformer is needed? what type?

By anon44613 — On Sep 09, 2009

Why does a voltmeter connect in parallel and an ammeter connect in series?

By anon44539 — On Sep 08, 2009

when is the difference between ac/dc used?

By shubhamb1994 — On Sep 02, 2009

Who discovered AC and DC and in which year?

By anon43293 — On Aug 27, 2009

In the conversion of a.c to d.c, how high is the d.c current compared to a.c current?

By anon43291 — On Aug 27, 2009

why is current high in d.c but low in a.c.?

By anon42993 — On Aug 25, 2009

I know that the DC current is unidirectional whereas the AC current is bidirectional. My question is, in AC, whether the current will flow from the phase to neutral? If so then why it is not indicated by the indicator when placed in the neutral; terminal of the socket?

By anon42819 — On Aug 24, 2009

what happens to the electrons when ac current flows through a conductor? Do they oscillate about their mean position or do they travel from one end to the other?

By anon42817 — On Aug 24, 2009

when ac current reverses what happens? does it go back through the same conductor from where it was coming?

By anon40561 — On Aug 09, 2009

which countries use a/c and which use d/c

By sherzod — On Aug 05, 2009

DC is just as harmful as AC, as long as voltage, amperage, hertz (a.k.a.) "Frequency of the current" are the same.

By anon39702 — On Aug 03, 2009

which is more harmful to human body ac or dc and why?

By anon39225 — On Jul 31, 2009

which is more harmful to human body, ac or dc? and why?

By sherzod — On May 08, 2009

response to anon7774:

I will try answer it: the current that you get from hot wire comes only from hot wire and it does not go back, it goes out through neutral wire.

Electrons within the wire are the ones that change the direction, because of the magnetic field from generator, as long as electrons are in order by a magnetic field, you will get your current.

By anon30186 — On Apr 15, 2009

Very nice article. I liked it very much. It is short and understandable. And very practical.

By thudins — On Mar 31, 2009

Why will DC not harm you, but AC will?

By hullo909 — On Jan 17, 2009

I hope this is what you mean "anon3951".











(The dots indicate blank spaces.

The net resistance between B and C(the direction of flow of current) is 6 ohms, as there is no current flowing through AD (Wheatstone Bridge). Hence two 12 ohm resistors are in parallel. I hope i've answered your problem.

By anon21798 — On Nov 21, 2008

Moving charge in a magnetic field will experience a force, in other words, if the wire (or any conductor) is moving in the magnetic field, a force will be experienced by the electrons in the conductor, causing them to move; hence causing a current to flow (in the opposite direction).

By anon21760 — On Nov 21, 2008

give the different ways on how electricity generated in AC and DC.

By anon19056 — On Oct 05, 2008

There is no difference in ac and dc wiring

By anon15046 — On Jun 30, 2008

what type of current is flowing through a fluorescent lamp?

By aallafi2000 — On Jun 10, 2008

what is the difference between AC and DC conductivity?

By dennisc — On May 18, 2008

question: when checking charger for a battery that has DC current, when i put my charger on AC it goes to DC and reads 15dc does that mean the charger is good?

By anon7774 — On Feb 02, 2008

Hey, I am not clear about the AC current. When the current comes from the outlet into my fridge through hot wire, then what happens to it when it changes the direction? Does it go back to outlet through the hot wire? Then where does it go back from the outlet? And what happens to the neutral wire when the current is changing its direction?

By anon7445 — On Jan 26, 2008

Is there any difference in AC and DC wiring? If yes, how one can differentiate it?

By anon7041 — On Jan 16, 2008

Which one would glow more brightly-a bulb in ac or in dc?

By anon6122 — On Dec 17, 2007

which is more dangerous and why ?


By pgeddes — On Oct 19, 2007

I used 6 ga. AC wire to connect an inverter to the batteries in my RV. Will the AC wire be OK (it does seem to work OK) or will it cause some problem since I did not use 6 ga. DC wire? I think the main problem is that the AC wire is much stiffer and harder to work with than DC wire. If that is the only disadvantage it is behind me since the installation is complete.

By anon3951 — On Sep 25, 2007

Hi maybe you could show me how to figure out this problem. Four resistors of 6 ohms each form the sides of a diamond. A fifth resistor of 10 ohms the long diagonal of the diamond. What is the resistance of the combination between the ends of the long diagonal? What is the resistance between one end of the long diagonal and one end of the short diagonal?

By basictest — On Aug 11, 2007

What are the safety measures in using voltmeter?

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