Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Direct Current shopping experience:
1. Compare - without doubt the biggest advantage that the Direct Current offers shoppers today is the ability to compare thousands of Direct Current at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Direct Current? Wrong! If the Direct Current is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Direct Current then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Direct Current? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Direct Current and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Direct Current wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Direct Current then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Direct Current site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Direct Current, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Direct Current, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
Direct current (
DC or "
continuous current (electricity)") is the constant flow of
Electric charge . This is typically in a
Conductor (material) such as a wire, but can also be through
semiconductors, Electrical insulations, or even through a vacuum as in
Electron beam. In direct current, the electric charges flow in the same direction, distinguishing it from alternating current (AC). A archaism for
direct current was
Galvanic current.
image:TypesOfDirectCurrentDiagram.pngThe first commercial electric power transmission (developed by
Thomas Edison in the late
19th century) used direct current.Because of the advantage of alternating current over direct current in transforming and transmission, electric power distribution today is nearly all alternating current. For applications requiring direct current, such as
third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current.
See 'War of Currents
.
Various definitions
Within
electrical engineering, the term DC is a synonym for "constant". For example, the voltage across a DC voltage source is constant as is the current through a DC current source. The DC solution of an electric circuit is the solution where all voltages and currents are constant. It can be shown that any voltage or current waveform can be decomposed into a sum of a DC component and a time-varying component. The DC component is defined to be the average value of the voltage or current over all time. The average value of the time-varying component is zero.
Although DC stands for "Direct
Current", DC sometimes refers to "constant polarity." With this definition, DC voltages can
vary in time, such as the raw output of a rectifier or the fluctuating voice signal on a telephone line.
Some forms of DC (such as that produced by a voltage regulator) have almost no variations in voltage, but may still have variations in output
electric power and current.
Applications
Direct current installations usually have different types of
sockets,
switches, and
fixtures, mostly due to the low voltages used, from those suitable for alternating current. It is usually important with a direct current appliance not to reverse polarity unless the device has a
diode bridge to correct for this. (Most battery-powered devices do not.)
High voltage direct current is used for long-distance point-to-point power transmission and for Submarine power cables, with voltages from a few kilovolts to approximately one megavolt.
image:Direct current symbol.svgDC is commonly found in many low-
voltage applications, especially where these are powered by battery (electricity), which can produce only DC, or
solar power systems, since
solar cells can produce only DC. Most automotive applications use DC, although the alternator is an AC device which uses a
rectifier to produce DC. Most
electronics circuits require a DC power supply. Applications using fuel cells (mixing hydrogen and oxygen together with a catalyst to produce electricity and water as byproducts) also produce only DC.
Most
telephones connect to a twisted pair of wires, and internally separate the AC component of the voltage between the two wires (the audio signal) from the DC component of the voltage between the two wires (used to power the phone).
Telephone exchange communication equipment, such as DSLAM, uses standard -48V DC power supply. The negative polarity is achieved by Ground (electricity) the positive terminal of power supply system and the Battery (electricity) bank. This is done to prevent
electrolysis depositions.
An electrified third rail can be used to power both
Rapid transit and overground trains.
See also
External links
- " AC/DC: What's the Difference?".
Direct current (
DC or "
continuous current (electricity)") is the constant flow of
Electric charge . This is typically in a Conductor (material) such as a wire, but can also be through semiconductors, Electrical insulations, or even through a
vacuum as in Electron beam. In direct current, the
electric charges flow in the same direction, distinguishing it from alternating current (AC). A archaism for
direct current was
Galvanic current.
image:TypesOfDirectCurrentDiagram.pngThe first commercial
electric power transmission (developed by Thomas Edison in the late 19th century) used direct current.Because of the advantage of alternating current over direct current in transforming and transmission, electric power distribution today is nearly all alternating current. For applications requiring direct current, such as
third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current.
See 'War of Currents.
Various definitions
Within electrical engineering, the term DC is a synonym for "constant". For example, the voltage across a DC voltage source is constant as is the current through a DC
current source. The DC solution of an
electric circuit is the solution where all voltages and currents are constant. It can be shown that any voltage or current waveform can be decomposed into a sum of a DC component and a time-varying component. The DC component is defined to be the average value of the voltage or current over all time. The average value of the time-varying component is zero.
Although DC stands for "Direct
Current", DC sometimes refers to "constant polarity." With this definition, DC voltages can
vary in time, such as the raw output of a rectifier or the fluctuating voice signal on a telephone line.
Some forms of DC (such as that produced by a
voltage regulator) have almost no variations in voltage, but may still have variations in output
electric power and current.
Applications
Direct current installations usually have different types of
sockets,
switches, and
fixtures, mostly due to the low voltages used, from those suitable for alternating current. It is usually important with a direct current appliance not to reverse polarity unless the device has a
diode bridge to correct for this. (Most battery-powered devices do not.)
High voltage direct current is used for long-distance point-to-point power transmission and for Submarine power cables, with voltages from a few kilovolts to approximately one megavolt.
image:Direct current symbol.svgDC is commonly found in many low-voltage applications, especially where these are powered by battery (electricity), which can produce only DC, or
solar power systems, since solar cells can produce only DC. Most automotive applications use DC, although the
alternator is an AC device which uses a rectifier to produce DC. Most
electronics circuits require a DC
power supply. Applications using
fuel cells (mixing hydrogen and oxygen together with a catalyst to produce electricity and water as byproducts) also produce only DC.
Most
telephones connect to a twisted pair of wires, and internally separate the AC component of the voltage between the two wires (the audio signal) from the DC component of the voltage between the two wires (used to power the phone).
Telephone exchange communication equipment, such as
DSLAM, uses standard -48V DC power supply. The negative polarity is achieved by Ground (electricity) the positive terminal of power supply system and the
Battery (electricity) bank. This is done to prevent
electrolysis depositions.
An electrified third rail can be used to power both Rapid transit and overground trains.
See also
External links
- " AC/DC: What's the Difference?".
Direct current - Wikipedia, the free encyclopedia
Direct current (DC or "continuous current") is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and ...
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