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Eric Quinn
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Electricity 101 |
| You might be a routing table guru, but do you know the basics of electricity and how it can affect your network? |
| by Eric Quinn |
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3/18/2003 -- When it comes to facilities management there are those who know what to do and those who scratch their head. Maintaining the infrastructure of plumbing and electrical circuits is just as confusing to the uninitiated as routing tables are. Because of the increased globalization of today's corporations, its important to understand how everything can affect your network, including electricity, a vital component.
Electricity can be divided into categories, depending on how powerful it is and how it was designed to behave. There are three main categories you need to understand: AC vs. DC, Voltage and Hertz. Each one has the potential to make or break your network because most electrical components are designed to work only with specific types of electricity. Look at the back of a printer. There will probably be a single value for voltage (v) and for Hertz (Hz). If there is a range of values then the device will work with multiple values. For example, my printer will work only with 110v but with 50-60 Hz. But just what do these values mean?
Voltage is electrical pressure and is one component of total power. How much electricity a device gets is a function of the pressure forcing the electricity down the line. Voltage forces amperage (amps) into a device. The total power received is measured in watts and is equal to volts times amps. A 110v device receiving 1 amp just received 110 watts of power. A 220v device receiving 1 amp receives 220 watts of power. Same amount of power being transferred but because the pressure or voltage was twice the amount, the second device receives twice the effect. This makes it dangerous to plug a device that wants 1 amp and is rated for rated for 110v into a plug rated at 220v. The device will suck up 1 amp and will probably burn out because the pressure is too great. The reverse is also true but the device may not operate due to not receiving enough power.
Alternating Current (AC) and Direct Current (DC) may both be used to operate a device. AC operates in a sine wave where the voltage fluctuates from a positive peak to a negative peak. ON a circuit rated for 110v, the sine wave will fluctuate from +110 to -110 (The peak to peak value is actually higher because of the curvature of the wave). How often this wave cycles is the Hertz or cycle frequency. The western hemisphere mostly uses electricity operating at 60 Hz while the Eastern hemisphere mostly uses 50 Hz. This means that the fluctuation occurs more rapidly in the U.S. than it does in the U.K.
AC is the preferred method of delivering electricity because devices can be used to break the voltage down into smaller pieces. A transformer can be used to break 220v AC down to 110v AC. High voltage lines can be used to deliver 15,000v to a neighborhood and local transformers will break the electricity down for the homes. DC doesn't have the cycle variation, a 220v DC flow is always +220v. Because there is no variation, there is no way to break the voltage into smaller pieces. AC can be converted into DC simply by lopping off the negative voltage and smoothing out the positive peak but 50 Hz can't be changed into 60Hz.
Some devices are equipped to sense the incoming voltage, configure themselves and use it. Others don't have that mechanism built in. Other devices may run off DC voltage and won't care how the original AC was made. 50Hz or 60, it all gets turned into DC and the device using the electricity never notices. This is why most laptops, portable CD players and handheld game players can work anywhere. They run off DC and AC is used to recharge or for conversion.
The real problem people run into is with the Hz. AC can be used to create a magnetic field to keep a motor turning. If the Hz is incorrect, the motor will turn too fast or too slow. This may not be much of a problem with a small handheld drill but what does it do to a hair drier? You can set your PC's power supply to interact with 220v/50Hz but what about your printer? Will it work okay after the transformer has converted the voltage?
You can purchase transformers that will convert voltage from one value to another. Some transformers will only convert one way, say from 110v to 220v or vice versa and would be referred to as a step-up or step-down transformer. Others can transform voltage in either direction. You also need to know what the voltage is like where the work will be done. Japanese voltage runs at 110v while voltage up to 250 can be found in India and South Africa. There's typically a little bit of slop allowed, most devices from the US will run fine on the Japanese 100v, but be careful going up with precision devices. 
Questions? Comments? Post your thoughts below!
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Eric Quinn, CCNP, CCDP, CCSI, is a security instructor and consultant. He is also co-author of the CCNP Remote Access Exam Cram by Coriolis Press. He writes the “Link State Update” column for TCPmag.com, and is a contributing editor for CertCities.com. Reach him at .
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There are 11  user Comments for “Electricity 101”
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| 3/20/03: Steve Olson from Harrisburg, Pa says: |
Not a very good article. For example, "Voltage forces amperage (amps) into a device" is incorrect for two reasons. "Voltage forces amperage" should actually read "Voltage forces current, which is measured in amperes (amps). Current flow is a more universal term. Also, it's not so much as the voltage forcing current through as it is the resistance of the device causes the current flow. This resistance is measured in ohms. How can you write an article on the basics of electricity without ohms?? This leads to another error. You state "This makes it dangerous to plug a device that wants 1 amp and is rated for rated for 110v into a plug rated at 220v. The device will suck up 1 amp and will probably burn out because the pressure is too great." Completely incorrect. The device is using 1 amp @ 110v because it has an internal resistance of (I=e/r) 110 ohms. If plugged into a 220v circuit, the device will draw 2 amps. The device will burn up because it has twice the current flowing through it. |
| 3/21/03: D. Collison from Albany, NY says: |
I agree with the first writer, Steve Olson from PA. The article's wording is ambiguous and basically incorrect in a couple of places. And how can you talk about electricity without at least memtioning Ohms?? From what I remember in school, voltage, current and resistance ARE the three variables electricity consists of. |
| 3/25/03: A. C. Smith from Davenport, IA says: |
The article has a good concept behind it. If your an infrastructure manager, an SA or NA or a hardware tech you need to understand the fundamentals of electrical power. This is especially true if you support global users as I do. Unfortunately this article is insufficient for the purpose, both in space allotted and technical accuracy. A series of good articles would be welcome. |
| 4/19/03: pnug from UK says: |
The article probably raises dangerous issues in that you call it electricity 101. Well Im an electrical engineer changing careers to the IT industry and the author knows very little about electricity. I could write an article on electricity distribution and application within IT but I couldnt write an IT article. Im not good enough yet. The responedents have a better idea. The 3 fundamentals of power are voltage, current and reseistance. These make up the power triangle. Lets not even mention Hz at this stage as we get into harmonics, non sinusoidal loads, ups's and self generation. Which should all be considered for the lkarge enterprise. If you want to write an article write about something you know about. Generally the articles here are pretty good but this is dagerous and obviously well outside the authors scope of expertise. Stick to what your good at. The safest thing for all concerned would be to remove the article. A final point if someone comes along and can physically plug a 110volt device into a 220 volt power source someone shoild be fired. That why we have different connectors. Yes there are universal connectors but these are for equipment with auto sense to detect the voltages. |
| 5/5/03: T Fletcher from Philadelphia, PA says: |
In addition to the previous issues, a 110v circuit oscillates between +110 and 0, not -110 as stated in the article. A circuit that oscillates between +110 and -110 would be 220v. |
| 5/29/03: Ollie Cox from UK says: |
T Fletcher has it wrong too! Have a look at a good Australian site www.phys.unsw.edu.au/~jw/power.html which says the following:- "When talking of AC, RMS values are so commonly used that, unless otherwise stated, you may assume that RMS values are intended*. For instance, normal domestic AC in Australia is 240 Volts AC with frequency 50 Hz. The RMS voltage is 240 volts, so the peak value Vm= V.21/2 = 340 volts. So the active wire goes from +340 volts to -340 volts and back again 50 times per second. (This is the answer to the teaser question at the top of the page: rectification of the 240 V mains can give both + 340 Vdc and -340 Vdc.) "* An exception: manufacturers and sellers of HiFi equipment sometimes use peak values rather than RMS values, which makes the equipment seem more powerful than it is." |
| 1/3/04: George Franklin from England says: |
This title suggested a link with what a network engineer needs to know with regards electricity and the effects on a network. Well, where was the Network part, surely it would have been good to mention UPS and Residual circuit breakers etc and that all companies require a qualified electrician to undertake ANY electrical work, unless you want to be sued! I suggest discussing electrical load and the effects of motors on a circuit causing interference a more interesting topic, i.e. The need for proper planning with regards to power points and the dangers of fire due to using to many units on extension leads, who has worked in a company at some time that has 3 or 4 things plugged into one extension. You can’t discuss electricity without compared it to a water pumped system and anyone who works looking after a network knows the biggest problem is heat and that all network devices fail due to lack of air ventilation or non air conditioned areas. All circuits are unstable and devices struggle to maintain a suitable supply voltage, with digitals circuits the effects of oxidation and heat will degrade any circuit, however with today’s throw away production attitude, a device is scrapped after 3 years of service as it is most likely to fail due to it MTF time. Proper network planning should start with proper electrical inspection and socket positions, such that it is not on the same ring or radial as other office equipment. Also the electrical circuit should have a measuring device to keep an eye on any spikes or surges, voltage drops. If you don’t have ALL network devices on UPSs on your network, I suggest you make the suggestion to your IT Boss since he’s more likely to give you a pay rise when you remind him of the recent power Cut! , I also agree with the others you need to mention resistance, without resistance you couldn’t control or limit the flow of current and actually is probably the most important element to understanding electricity. |
| 1/3/04: George Franklin from England says: |
This title suggested a link with what a network engineer needs to know with regards electricity and the effects on a network. Well, where was the Network part, surely it would have been good to mention UPS and Residual circuit breakers etc and that all companies require a qualified electrician to undertake ANY electrical work, unless you want to be sued! I suggest discussing electrical load and the effects of motors on a circuit causing interference a more interesting topic, i.e. The need for proper planning with regards to power points and the dangers of fire due to using to many units on extension leads, who has worked in a company at some time that has 3 or 4 things plugged into one extension. You can’t discuss electricity without compared it to a water pumped system and anyone who works looking after a network knows the biggest problem is heat and that all network devices fail due to lack of air ventilation or non air conditioned areas. All circuits are unstable and devices struggle to maintain a suitable supply voltage, with digitals circuits the effects of oxidation and heat will degrade any circuit, however with today’s throw away production attitude, a device is scrapped after 3 years of service as it is most likely to fail due to it MTF time. Proper network planning should start with proper electrical inspection and socket positions, such that it is not on the same ring or radial as other office equipment. Also the electrical circuit should have a measuring device to keep an eye on any spikes or surges, voltage drops. If you don’t have ALL network devices on UPSs on your network, I suggest you make the suggestion to your IT Boss since he’s more likely to give you a pay rise when you remind him of the recent power Cut! , I also agree with the others you need to mention resistance, without resistance you couldn’t control or limit the flow of current and actually is probably the most important element to understanding electricity. |
| 3/4/04: Anonymous says: |
what are the effects of using a 60 hz motor on 50 hz supply? |
| 5/25/04: Anonymous says: |
Does anyone know of a good Electricity 101 link! |
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