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by Ron Kurtus

A total of 724 comments and questions have been sent in. They are listed according to date.

You can read them to further your understanding of the subject.

List of next 10 letters




AC World Voltages Can i use a 110-220v appliance on 240v Australia
AC World Voltages Using 220 volts in India Saudi Arabia
DC Coupling two DC sources together India
AC Where do AC electrons go? Australia
AC Transformers What are five uses of a transformer? India
AC World Voltages Correction on AC frequency history in UK UK
AC World Voltages AC frequency fluctuation India
AC World Voltages Why does the US use 60Hz AC? India
AC World Voltages Cited article on voltages Australia
AC Transformers Can I use AC transformer to convert DC to AC India

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First 10 letters

Can i use a 110-220v appliance on 240v

Topic: AC World Voltages


August 23, 2014

can i use a 110-220v appliance on 240v

claude - Australia



A 220 volt appliance should be able to work on 240 v. However, you need to make sure they both have the same outlet plugs.

Also, if the frequency is different, the appliance may run at a different speed.

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Using 220 volts in India

Topic: AC World Voltages


August 11, 2014

Appliance says ' FREQUENCY SWITCHABLE 50 / 60 & VOLTAGE 220.
Does this appliance ( Refrigerator of SAMSUNG ) workable in India, since India follows 240 v & 50 cycle ?

masroor - Saudi Arabia



There is a tolerance or variation in voltage, so a 220 volt appliance should function in the 240 volt India voltage. However, you may need a plug adapter. I'm not sure what outlet plugs they use.

It is good to check with travel agencies for India to find out what outlets they use.

Best wishes on your travels.

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Coupling two DC sources together

Topic: DC


August 5, 2014

under what conditions can two dc sources can be coupled with each other?

velayudham - India



Ideally, you would want the DC sources to have close to the same voltage and current output. Otherwise, you could damage the lower-leveled source.

For example, connecting a 10 volt battery to a 1.5 volt battery would probably damage the 1.5 volt battery and create a short circuit.

Also, of course, the terminals should be plus (+) to minus (-).

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Where do AC electrons go?

Topic: AC


July 14, 2014

The diagram (above) showing how AC moves through transmission wires is missing.

If the electrons move back and forth how do they go anywhere?

Drew - Australia



The animation showing how AC electrons move back and forth in a wire requires a Flash plugin. I plan to have a new animation without requiring Flash soon.

While in a DC circuit, electrons enter the battery or DC generator at the (+) terminate and exits at the (-) terminal. But in an AC circuit, the electrons simply move back and forth in the wire, starting at the AC generator. The motion of the electrons--and their electromagnetic waves--then power any devices in a circuit.

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What are five uses of a transformer?

Topic: AC Transformers


June 20, 2014

5 uses of transformer

Harjinder singh - India



1. Transformers are used to increase voltage.
2. They can also be used to decrease voltage.
3. Signal and audio transformers are used to match voltage to the input of amplifiers.
4. Audio transformers allowed telephone circuits to carry on a two-way conversation over a single pair of wires.
5. A balun transformer can convertsa signal that is referenced to ground to a signal that has balanced voltages to ground.

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Correction on AC frequency history in UK

Topic: AC World Voltages


May 21, 2014

I stumbled upon your page and thought I should make some comments.

Your article states that the U.K. initially used 60Hz supplies and switched to 50Hz after World War II. In fact 50Hz was adopted as a standard in the 1920's for the National Grid, which came into operation during the 1930's to tie the country's previously fragmented generating networks together. Locally generated power in the early years used a variety of frequencies, but 50Hz was already in quite widespread use at this time. Certainly 60Hz was used in places, but it wasn't any sort of national standard as the article seems to imply, and other frequencies (e.g. 40Hz) were also employed.
All of these non-50Hz areas gradually converted to the 50Hz standard as they linked up with the National Grid.

As a side note, Britain still had local DC systems in the older parts of some towns into the 1950's and 1960's, although in decreasing numbers as time went past,

In the United States, some areas started out with frequencies other than 60Hz. Some parts of upstate New York used 25Hz, for example, which resulted in much more expensive transformers and other difficulties. Some parts of the West Coast also had 50Hz local systems at one time, e.g. Los Angeles used 50Hz until conversion to 60Hz in the 1920's or early 1930's.


Paul - UK



Thanks for pointing out the mistake on the background of AC frequency in the UK.

I corrected the page Background of Worldwide AC Voltages and Frequencies concerning the UK switching to 50Hz after WWII.

The history of selecting voltages and frequencies gets quite convoluted. I'll try to add some details like you have given at a later date.

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AC frequency fluctuation

Topic: AC World Voltages


May 3, 2014

1- what is the relation between frequency, voltage & current ?
2- why frequency fluctuate 48.5hz to 51.5hz ?
3- why generator speed didn't fluctuate with load fluctuation ?

Manas Ranjan - India



Frequency of AC is independent of voltage and current. The frequency fluctuates primarily because the generator speed may vary slightly. Also variation in load can affect the generator speed.

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Why does the US use 60Hz AC?

Topic: AC World Voltages


April 20, 2014

1) Why usa use 120volt 60 hertz instead of 50hertz? What is the reason behind this?

lomesh - India



The lesson Background of Worldwide AC Voltages and Frequencies explains that most countries originally used 60Hz, but then a major electrical supplier wanted to use 50Hz. Many countries switched over, even though is 50Hz was less efficient. The United States stayed with the more efficient 60Hz.

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Cited article on voltages

Topic: AC World Voltages


March 13, 2014

I have cited your article ( as a reference in the Wikipedia article "Schuko", concerning the German Schuko plug.
This is in relation to the use of 220 V centre tapped supplies (giving dual out of phase 110 V - above earth - supplies) in Europe up until the 1950s.
If possible, could you provide a reference to a primary source of this information, since I have not found it as a reference in your article "Background of Worldwide AC Voltages and Frequencies"

Peter - Australia



Thanks for citing the article on AC voltages.

References concerning the change in European voltages include: and

I plan to add information on the Schoko and other electrical outlets in the near future.

I hope this helps.

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Can I use AC transformer to convert DC to AC

Topic: AC Transformers


February 28, 2014

can we use th ac transformer structure for a 7v dc input nd higher ac output??

arpan - India



A Power Inverter us used to convert DC to AC. Some people use them in their automobiles to power small electronic devices requiring AC from the DC battery.

Although inverting 7 V DC is possible, there may not be enough current.

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