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Basic example of electricity (C) Carson Dunlop Associates Electrical Definitions FAQs

Q&A about Amps, Volts, Watts, Ground, Phase, Resistance and more

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Questions & answers about the definitions of common electrical terms including amps, volts, watts, resistance, current, ohms, electrical phases. .

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Electrical Amps, Volts (Current), Resistance (Ohms), Watts & Electrical Phase FAQs

Question: how to convert AC amps to DC Amps or vice versa

Is 1 amp AC equal to 1amp DC? My golf club stores the batteries for member's walking power carts. There are about 20 battery chargers and batteries plugged into one AC circuit that is presumably a 15 amp circuit.

My charger has a 2 amp output to the battery and the others are probably the same.

If all of the batteries needed charging at the same time, drawing 40 amps, then the batteries would have to share the available 15 amps resulting in a very slow charge.
Am I correct? (May 26, 2015) Mike L

Reply:

Technically AC & DC amps are not precisely equivalent.

The DC amperage draw will be slightly less than AC. For example if you are selecting an electrical switch capable of handling 5A at 125VAC, it should be fine to use that switch on a DC current since the actual DC amperage draw will be a bit under 5 amps.

Power = Amps x Volts regardless of AC or DC.

20A at 120VAC = 240 Watts (power)

Also the amperage rating of a switch is increased as the voltage is decreased.

Example: a 120VAC 5-Amp switch can handle about 600 Watts and according to batterystuff.com's calculator, supports a 12-Volt DC amperage of 55.

 

Question: how to calculate the operating cost of a well pump and booster pump

Is there a formula i can use to calculate the cost of a water well pump, and a booster pump? (June 18, 2015) barry s

I havec a question about calculating a well pump and booster pump for cost. i didn't receive an answer so i put my e-mail, by the way you do an excellent job on teaching basic electrical, keep up the good work. thanks barry 2000hrs 6-18-2015 bbrechbiel1950@gmail.com

Reply: Here's the formulat for well pump operating cost measured in watt-hours

To convert the current draw (from the pump data tagor by actual measurement) to watts and watt hours to relate the electricity usage to what appears on your electric meter and electric bill in watt hours:

Energy E in watt-hours (Wh) = Power P (in watts W) x time period t in hours (h), or

E (Wh) = P(W) x t (h)

 

Question: is it ok if a power inverter produces more amps than my application requires?

In selecting inverters for a specific product I know the Volts need to be the same, but as for the amps....if your inverter produces more Amps than needed, is this a problem? (July 5, 2015) layne said:

Reply:

Layne

No not as I understand it; the amps rating is the maximum amount of current draw or demand that can be asked of the inverter. If your application draws less current that's ok.

 

Question: What do I need to hook up DC running lights and a porch light on a gutted Airstream International trailer?

I have a 1967 Airstream International planted in the backyard and want to run an extension cord out to it to run basic electric.

It has 5 amber running lights and a porch light on the outside that runs on DC. It is completely gutted and I have access to the single wire from each fixture.

What do I need to do to hook up the outside running lights to a power strip. - Rob

Reply: AC - DC power converter, extension cord, connectors, caution

Rob,

At your local electrical supplier or auto supply store or even at Radio Shack you should be able to pick up a small External AC to DC power converter (aka AC to DC Power Supply). What you need is a converter that will have high enough Amps output for the few trailer lights that you cited.

I used the term "External AC to DC Power converter or power supply because you don't want to have to buy a separate cabinet or case and do assembly. When shopping don't rule out existing computer or other electronic power supply "bricks" - just take a look at the DC Wattage output that the supply can provide. If it's big enough you'll be OK.

For just a few running lights and a porch light, most likely you won't even be drawing 10 watts, but to be on the safe side and to allow for expanded use of your power supply once you figure out how useful it is, I'd look at a unit with 35 watts or larger output.

Take a look at our DEFINITIONS of ELECTRICAL TERMS beginning at the top of this page for help with AC, DC, Amps, and Watts.

Run a weather-resistant outdoor-rated extension cord from an outdoor GFCI protected receptacle over to the Airstream and inside it where it will be weather protected.

To that 120V (probably 15A) circuit, you'll plug in your AC to DC Converter. You'll then wire the DC output terminals to your Airstream lighting circuit.

If you're going to use this electrical supply system frequently you might want to put together a suitable plug connection feeding the DC powered circuit and a suitable connector on the wires that you run from the AC-DC converter.

For more permanent power conversion of an older Airstream or other mobile home or trailer, I'd look at what's offered by RV suppliers.

Certainly I had no trouble retrofitting an AC to DC connector and power supply on an old slide-on pickup truck camper, thus allowing us to "plug in" to any 120V DC power source and run all of the DC devices in the camper.

Is a car battery AC or DC?

Does a 12 volt car battery provide AC or DC current On 2017-05-19 by Ravi -

Reply by (mod) - what kind of current is provided by a car battery?

Thanks for the question, Ravi: a 12 volt car battery provides DC current.


Where is heat generated in an electrical wire: the conductor, the insulator, or both?

Does a insulator generate more heat than a conductor and why?

I mean same volt,b ut the insulator has greater resistance and lower ampere.and just apposite for the conductor.

Naturally the conductor should generate more heat.

AN electric wire carrying even 150 amp should be blown. On 2014-01-29 by Anonymous

Reply by (mod) - electrical conductors do heat up

Anon, electrical conductors do heat up - from current flowing through the wire.

An insulator does not *generate* heat because it is not conducting electricity. Electricity wants to flow through the path of least resistance: in this case, the metal conductor wire.

Rather the insulator prevents the wire from short-circuiting and causing a fire or shock as the current-carrying conductor runs through a building (or through anything else).

Electrical wire insulation in fact must be designed and rated to withstand the heat expected to be generated when a wire of a given size is used with a given current flow measured in Amps.

That's why using an over-sized fuse or circuit breaker is a fire hazard: if we permit more current to flow through a wire than it is designed to carry safely, the wire may overheat, damaging its insulation and shorting or otherwise causing a fire.


Why doesn't a 400A electrical conductor get hot when carrying 100A?

A electric conducter may carry 400 amperes.what does it mean? why it is not heated up when it is carrying 100 amperes? On 2014-01-29 by atmadhi -

Reply by mod: your question is stated improperly: wires do get warm or hot when carrying current.

Electrical wires are warmed when carrying current, Atmadhi.

Just how much heat is generated depends on the current flow (amps) and the wire resistance (ohms), and the wire temperature, in turn, will be affected by its ability to transfer some of that heat to the surrounding environment (air, water, concrete, or whatever material through which the wire passes).

Thank you to our readers for their generous comments

On 2013-01-27 by Pauli

This is a fantastic site - thanks for sharing your knowledge and expertise!

I think the 350W may be a typo since you state that 120V x 15A = 1800W - unless I am misinterpreting or missed something.

"15-Amp 120V electrical circuits: typical U.S. 120V household electrical circuit uses #14 gauge copper wire and is protected (and thus limited) by a 15-amp circuit breaker. Such a circuit can deliver about 350 watts of electrical power to devices plugged into it, and another roughly 10 watts is consumed by the resistance of the circuit and its devices (receptacles and switches)."

This is a fantastic site - thanks for sharing your knowledge and expertise!

On 2011-12-23 by gc

awesome explanations, thank you very much, I now understand the basics of electricity

On 2011-06-29 by Josh

Great description, thanks

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