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Thread: Amps vs. Watts vs. Volts?

  1. #1

    Default Amps vs. Watts vs. Volts?

    Can someone point me to an "electronics for dummies" type page, or explain this to me? I still after all these years don't understand the difference between these. My dad has tried to explain it to me several times with little success. :-(

    Thanks in advance!

  2. #2
    Flashaholic*
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    Default Re: Amps vs. Watts vs. Volts?

    Lemme have the honour of taking up the challenge. Let's take electricity as water. Wire as garden hose.

    Voltage is amount of pressure. So more voltage, more pressure, water shoot out of hose faster.

    Ampers is amount of water. Bigger hose, more water can flow at one time.

    To make it as unconfusing as possible, take your normal everyday garden hose: You pinch it, you get higher voltage, you change hose to bigger hose, more water can flow, but that doesn't = higher voltage because water may flow slower instead.

    Watts = total amount of water flowing and at what speed = Volts x Amps.

    Tell me which part do you not understand and I'll see if I can simplify it some more.

  3. #3

    Default Re: Amps vs. Watts vs. Volts?

    "To make it as unconfusing as possible, take your normal everyday garden hose: You pinch it, you get higher voltage, you change hose to bigger hose, more water can flow, but that doesn't = higher voltage because water may flow slower instead."

    No, pinching it adds resistance, voltage stays the same, current drops.

  4. #4

    Default Re: Amps vs. Watts vs. Volts?

    The amount of worked performed by a circuit today was 100 watts.

    It did it with 100 amps. It didn't take much force since it had so many amps. It only took 1 volt.

    If there were only 50 amps, it would take twice as much force. It would take 2 volts.

    If there were only 25 amps, it would take four volts.

    ............................

    My men lifted 100 lbs today (watts). Their labor contract said they were only allowed to lift 1 pound each (amps). It took 100 men (1 volt each) to lift the 100 pounds.

    The labor union renegotiated, and they can now lift 2 pounds each (amps). It now only takes 50 men (2 volts each) to lift the 100 pounds.

    I'm trying to renegotiate for them to lift 4 pounds each (amps). That way, it will only take 25 men (4 volts each) to lift the 100 pounds.

    ........................

    Watts (the work done) = Amps (the resources consumed) times Volts (the strength of the resource units)

  5. #5

    Default Re: Amps vs. Watts vs. Volts?

    Let me throw this analogy at you:

    Electrons do the work and the more that come through a gate and the speed at which they pass through, the more work (watts) can be done. The gate restricts how many electrons can pass through at the same time. The gate (wire) size dictates this number and think of this number as amps. Now the electrons can flow through the gate at different speeds (voltage) and the faster they go through, the more energy or power they impart (Watts).

    Watts = Amps X Volts

    It helps me to think of the electrons moving through the wire as I can see that amperage capacity is then a function of wire size (how many electrons can fit in the gate or tunnel cross section) and then I visualize the speed at which they are moving as the voltage or velocity.

    To use this analogy further, consider a resistor or resistance as speed bumps [img]images/icons/grin.gif[/img] The electrons are slowed down at this point and a voltage drop occurrs. As the electrons hit the speed bumps and are slowed, energy is lost.

    Another reason I like to think of voltage being the velocity of the electrons is that I can visualize electrons speeding through a wire and if they come to a gap in the wire, the faster they are moving, the farther I can see them successfully jumping across this gap (arc). The greater the voltage, the greater the arc.

    The annoying static electricity is a result of a few, misbehaved electrons, going well in excess of the speed limit and doing Evil Kenevil stunts at our expense.
    [img]images/icons/tongue.gif[/img]

  6. #6

    Default Re: Amps vs. Watts vs. Volts?

    Thanks very much guys!!

  7. #7

    Default Re: Amps vs. Watts vs. Volts?

    Chris,
    Try to think in literal terms.

    Watts: The amount of work to do.

    Amperage: The resources (the number of electrons)you're working with.

    Voltage: The power (the muscle of each electron)of each unit of your resources.

  8. #8
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    Default Re: Amps vs. Watts vs. Volts?

    Ask 'em about resistor values now. [img]images/icons/tongue.gif[/img]

  9. #9

    Default Re: Amps vs. Watts vs. Volts?

    Ooh, the pretty colors... [img]images/icons/grin.gif[/img]

  10. #10

    Default Re: Amps vs. Watts vs. Volts?

    Black
    Brown
    Red
    Orange
    Yellow
    Green
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    Violet
    Gray
    White

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    Default Re: Amps vs. Watts vs. Volts?

    10kohm
    1kohm
    100ohm
    10ohm
    1ohm
    1milliohm...

    am i anywhere near the right track? [img]images/icons/wink.gif[/img]

  12. #12

    Default Re: Amps vs. Watts vs. Volts?

    "am i anywhere near the right track?"

    um, no.

  13. #13
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    Default Re: Amps vs. Watts vs. Volts?

    What is Electricity?
    By Dave Barry

    What in the world is electricity?

    And where does it go after it leaves the toaster?

    Here is a simple experiment that will teach you an important electrical lesson: On a cool, dry day, scuff your feet along a carpet, then reach your hand into a friend's mouth and touch one of his dental fillings. Did you notice how your friend twitched violently and cried out in pain? This teaches us that electricity can be a very powerful force, but we must never use it to hurt others unless we need to learn an important electrical lesson.

    It also teaches us how an electrical circuit works. When you scuffed your feet, you picked up batches of "electrons," which are very small objects that carpet manufacturers weave into carpets so they will attract dirt. The electrons travel through your bloodstream and collect in your finger, where they form a spark that leaps to your friend's filling, then travels down to his feet and back into the carpet, thus completing the circuit.

    Amazing Electronic Fact: If you scuffed your feet long enough without touching anything, you would build up so many electrons that your finger would explode! but this is nothing to worry about unless you have carpeting.

    Although we modern persons tend to take our electric lights, radios, mixers, etc. for granted, hundreds of years ago people did not have any of these things, which is just as well because there was no place to plug them in. Then along came the first Electrical Pioneer, Benjamin Franklin, who flew a kite in a lightning storm and received a serious electrical shock. This proved that lightning was powered by the same force as carpets, but it also damaged Franklin's brain so severely that he started speaking only in incomprehensible maxims, such as "A penny saved is a penny earned." Eventually he had to be given a job running the post office.

    After Franklin came a herd of Electrical Pioneers whose names have become part of our electrical terminology: Myron Volt, Mary Louise Amp, James Watt, Bob Transformer, etc. These pioneers conducted many important electrical experiments. For example, in 1780 Luigi Galvani discovered (this is the truth) that when he attached two different kinds of metal to the leg of a frog, an electrical current developed and the frog's leg kicked, even though it was no longer attached to the frog, which was dead anyway. Galvani's discovery led to enormous advances in the field of amphibian medicine. Today, skilled veterinary surgeons can take a frog that has been seriously injured or killed, implant pieces of metal in its muscles, and watch it hop back into the pond just like a normal frog, except for the fact that it sinks like a stone.

    But the greatest Electrical Pioneer of them all was Thomas Edison, who was a brilliant inventor despite the fact that he had little formal education and lived in New Jersey. Edison's first major invention in 1877, was the phonograph, which could soon be found in thousands of American homes, where it basically sat until 1923, when the record was invented. But Edison's greatest achievement came in 1879, when he invented the electric company. Edison's design was a brilliant adaptation of the simple electrical circuit: The electric company sends electricity through a wire to a customer, then immediately gets the electricity back through another wire, then (this is the brilliant part) sends it right back to the customer again.

    This means that an electric company can sell a customer the same batch of electricity thousands of times a day and never get caught, since very few customer take the time to examine their electricity closely. In fact the last year any new electricity was generated in the United States was 1937; the electric companies have been merely re-selling it ever since, which is why they have so much free time to apply for rate increases.

    Today, thanks to men like Edison and Franklin, and frogs like Galvani's, we receive almost unlimited benefits from electricity. For example, in the past decade scientists developed the laser, an electronic appliance so powerful that it can vaporize a bulldozer 2,000 yards away, yet so precise that doctors can use it to perform delicate operations to the human eyeball, provided they remember to change the power setting from "Vaporize Bulldozer" to "Delicate."

  14. #14

    Default Re: Amps vs. Watts vs. Volts?

    [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img]

  15. #15
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    Default Re: Amps vs. Watts vs. Volts?

    Originally posted by Empath:
    The amount of worked performed by a circuit today was 100 watts.

    It did it with 100 amps. It didn't take much force since it had so many amps. It only took 1 volt.

    If there were only 50 amps, it would take twice as much force. It would take 2 volts.

    If there were only 25 amps, it would take four volts.

    ............................

    My men lifted 100 lbs today (watts). Their labor contract said they were only allowed to lift 1 pound each (amps). It took 100 men (1 volt each) to lift the 100 pounds.

    The labor union renegotiated, and they can now lift 2 pounds each (amps). It now only takes 50 men (2 volts each) to lift the 100 pounds.

    I'm trying to renegotiate for them to lift 4 pounds each (amps). That way, it will only take 25 men (4 volts each) to lift the 100 pounds.

    ........................

    Watts (the work done) = Amps (the resources consumed) times Volts (the strength of the resource units)
    <font size="2" face="Verdana, Arial">Just to clarify it a little bit, watt is a unit of power. The actual work done is measured in watt-hours or watt-seconds. High power makes quick work.

    aa

  16. #16
    Flashaholic* Wingerr's Avatar
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    Default Re: Amps vs. Watts vs. Volts?

    That Dave Barry guy is a scream- Calvin and Hobbesque, only more so..

  17. #17
    Flashaholic
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    Default Re: Amps vs. Watts vs. Volts?

    Short form:
    V is voltage in, uhh, volts
    I is current in Amperes
    R is resistance in ohms
    W is power in watts

    Ohms law:
    V=I*R
    Power law:
    W=V*I or W=I^2*R (using ohms law)

    The rest is just different ways of arranging these equations.

  18. #18

    Default Re: Amps vs. Watts vs. Volts?

    Thank You People for such a nice & wonderFul explanation.
    i am on my way to understand this things.

    Still i need a few clarifications, pls. can anyOne help me out.


    1} In home sockets/plugs voltage is constant {240V in india}, so we just need to calculate & AmPs are given so we just need to calculate Power {Watts} with
    formula P = V*I.
    But sometimes this formula doesnt give accurate results.
    I just saw my SMPS, which is 450W & has 230V & 5A.

    Now according to the formula:
    V*I = W
    230*5 = 1150W



    This doesnt get equal to the one mentioned on the SMPS.

    y Is this so ??


    2} In Mobile phones or any device battery operated, how do we calculate electric consumption.
    'coz it is measured in mAh {1000mAh = 1Ah}, but it has variable voltage.
    & a lot others other things.

    its just a lot of confusing.

    Can someone pls explain in simple manner ?

  19. #19
    HKJ's Avatar
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    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by dharmil007 View Post
    Can someone pls explain in simple manner ?
    I am afraid that there is no simple explanation.

    With AC power the formula is not P=V*I, but need an added Power Factor (PF), this can also sometimes be called "cos phi".
    I.e. the formula is P=V*I*PF
    The PF is between 0 and 1.
    For resistors the PF is 1, for most other stuff it is less than 1. Some equipment is marked with the PF (or cos phi).


    When looking at ratings on the back of equipment the current is often specified to high. This value is used when you calculate the mains fuse, to avoid it blowing when you turn the equipment on.


    Battery supplied equipment does vary in how they draw their power:
    1) Some will draw a constant current, independent of voltage
    2) Some will increase current draw when voltage drops, i.e. using nearly constant power.
    3) Some will reduce current draw when voltage drops.
    If you look in my flashlight reviews you will see a chart showing current and power draw, depending on voltage.
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  20. #20
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    Default Re: Amps vs. Watts vs. Volts?

    I discovered something interesting the other day.

    Electrons move very slowly through wire!

    Its not the electrons doing the work so much as the magnetic field.

    The electrons appear to move at or near the speed of light, say, when you flick a switch, and the light comes on immediately, because they are all packed in the wire 'shoulder to shoulder' and pushing the first electron in line causes the last electron in line to move..

    but the speed of the electron is measured in feet per second! hard to believe, I know, counter-intuitive too, but check it out, Don.
    originally cpf member #14 write me at gmail.

  21. #21

    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by dharmil007 View Post
    Can someone pls explain in simple manner ?
    There are two ways of transmitting electricity through wires, direct and alternating current, DC and AC in short, you may have come across them. Direct current is where the direction of the current (travel of electrons) doesn't change, and alternating current is where the direction alternates. Imagine a straight wire. DC is where the current always flows to the left, for instance, whereas in AC the current will alternate in flow from right to left.

    DC current is used in small electrical devices powered by batteries, so the P=IV equation can be used directly. AC is used by power plants to transmit power to your sockets due to the ability of its voltage to be stepped up and down via transformers, reducing power loss during transmission (don't worry about this, it's not really that relevant to your question). The thing is since the current and voltage in an AC circuit always vary, they cannot be plugged directly into the P=IV equation. Instead, we have to take something called the root mean square value of the current and voltage, calculated by squaring the the values of one cycle of the oscillation, taking the mean (I won't go into detail) and then square-rooting it. Basically, this would give a value of current and voltage that is equivalent to the values in a DC circuit that does the same amount of work (i.e. power).

    Now as far as I know the AC current that we get from the mains follows that of a sine curve. Meaning the potential difference varies in a way that plotting the voltage against time on a graph would yield a sine curve. To obtain the RMS values for this type of AC circuit, it is simply dividing the maximum current or voltage by the square root of 2. The reason behind this will become clear when you see the graph. Therefore, to obtain the power of an AC circuit, meaning anything that's connected to the mains, the equation to follow is P=I(RMS)V(RMS), or P=[I(max)V(max)]/2.

    Try that and you should get the correct values in your picture.

    Regarding your second question, mAh represents how long a battery can sustain a particular current. 1000 mAh just means the battery can sustain a current of 1000 milli-amperes for one hour, 500 milli-amperes for two hours etc. Current alone isn't enough in determining how long your battery will last, you'll also need the voltage, and using that you can determine the amount of energy the battery has stored. Since it is a lithium ion battery, the potential difference between the two terminals is (for convenience's sake), 3.7V. So using P=IV, the battery has stored 3700 milli-watt hours of energy (power is work done per unit time). That means your battery has enough stored energy to keep a machine that draws 3700 milli-watts of power running for one hour. It's very very tricky to try to use this number to predict how long the battery will last, as like you mentioned, the power consumed by the phone varies according the usage and the PD across a Li-ion battery in reality isn't always 3.7V. However, if, say your phone lasts 10 hours on a single charge, you can estimate that it has consumed, on average, 370 milli-watt hours of energy, per hour
    Last edited by SPNKr; 06-03-2012 at 07:50 AM. Reason: Error in explanation

  22. #22

    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by SPNKr View Post

    Now as far as I know the AC current that we get from the mains follows that of a sine curve. Meaning the potential difference varies in a way that plotting the voltage against time on a graph would yield a sine curve. To obtain the RMS values for this type of AC circuit, it is simply dividing the maximum current or voltage by the square root of 2. The reason behind this will become clear when you see the graph. Therefore, to obtain the power of an AC circuit, meaning anything that's connected to the mains, the equation to follow is P=I(RMS)V(RMS), or P=[I(max)V(max)]/2.

    Try that and you should get the correct values in your picture.
    i Treid calculating, but it dint gave the answer.
    [I(max)*V(max)]/2
    [5*230]=1150/2=575W
    But the SMPS has 450W ??


    Quote Originally Posted by SPNKr View Post
    Regarding your second question, mAh represents how long a battery can sustain a particular current. 1000 mAh just means the battery can sustain a current of 1000 milli-amperes for one hour, 500 milli-amperes for two hours etc. Current alone isn't enough in determining how long your battery will last, you'll also need the voltage, and using that you can determine the amount of energy the battery has stored. Since it is a lithium ion battery, the potential difference between the two terminals is (for convenience's sake), 3.7V. So using P=IV, the battery has stored 3700 milli-watt hours of energy (power is work done per unit time). That means your battery has enough stored energy to keep a machine that draws 3700 milli-watts of power running for one hour. It's very very tricky to try to use this number to predict how long the battery will last, as like you mentioned, the power consumed by the phone varies according the usage and the PD across a Li-ion battery in reality isn't always 3.7V. However, if, say your phone lasts 10 hours on a single charge, you can estimate that it has consumed, on average, 370 milli-watt hours of energy, per hour
    Thanks for the explanation.
    But, This is not what i meant in the question
    Maybe i was too confused mySelf, so coudnt put it in proper terms.

    What i meant was :
    Voltage is used in supply.
    Then in mobile phones why it is the term that is used for drainage & it varies. ??


    & another question which i came through.

    i Have an AC, the trigger used for AC is of 25AmPs.
    When i used multimeter, it showed that while turning on AC, Amp had gone to 20AmPs & gradually came down to 10-12AmPs.
    So according to the formula my AC uses 2900W {240*12} or 2.9kW.
    i Need to calculate this on the input {trigger} or Output ???

    & this is how my Electric bill is calculated ???

  23. #23

    Default Re: Amps vs. Watts vs. Volts?

    I just did a little reading up, and found out 230V actually refers to the RMS value. I'm not sure why we don't get 450W, it could be that 450W refers to the output power, and some power is lost to resistance in the power supply. It could also be that it's mislabeled.

    Voltage is the potential difference between 2 points on a circuit, and in your phone it's referring to the PD between the two terminals of the battery. As I've mentioned before the terminal voltage of the battery varies according to how much it's charged, this is due to the chemistry of the battery. Li-ions are 4.2V when fully charged and the voltage slowly decreases as they're discharged. The voltage measurement is a way of telling you how full your battery is.

    I'm not quite sure what you mean by trigger, but if you're trying to measure the amount of work your device can do, you use the output. If you're interested in your electricity bills, measure the input. This is because the input of your devices is essentially the output of the power plant to your home, and they'll charge according to that.

    I just noticed this thread is 9 years old O.O

  24. #24
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    Default Re: Amps vs. Watts vs. Volts?

    As I wrote above: You cannot just multiply voltage and current to get power when working with AC, it only works for resistive loads (except if you do it fast enough)!

    This also means that you need special meters to measure power when working with AC, no ordinary DMM can do it.
    The meter needs to multiply voltage and current in real time and calculated the average of that. For digital meters that means measuring and multiplying voltage and current a few 1000's times each second.

    The green meter below can do that, the two other cannot:
    My website with flashlight, battery and charger information: lygte-info.
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  25. #25
    *Flashaholic* Mr Happy's Avatar
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    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by HKJ View Post
    The green meter below can do that, the two other cannot:
    The two yellow meters shown there are quite expensive. The green meter (a Metrahit Energy?) is very expensive!
    Tiefer, tiefer, irgendwo in der Tiefe gibt es ein Licht

  26. #26

    Default Re: Amps vs. Watts vs. Volts?

    Out of interest, what is the model number of the Fluke on the left?
    Is it still commercially available?

  27. #27
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    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by Mr Happy View Post
    The two yellow meters shown there are quite expensive. The green meter (a Metrahit Energy?) is very expensive!
    Yes, it is the Energy and the ability to measure Watt was the main reason I bought it (It can also measure the PF I wrote about). I do have other DMM's, even some more expensive, but none of them can measure Watt.
    There are a few other meters that can do Watt, but they are rather limited.

    Quote Originally Posted by peterharvey73 View Post
    Out of interest, what is the model number of the Fluke on the left? Is it still commercially available?
    It is the 189 and the other Fluke is the 289 that has replaced the 189 in the Fluke lineup.
    My website with flashlight, battery and charger information: lygte-info.
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  28. #28

    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by HKJ View Post
    ...
    It is the 189 and the other Fluke is the 289 that has replaced the 189 in the Fluke lineup.
    So the 189 has replaced the "179" in the Fluke line up???
    I notice you do have a 179.
    The 189 is a new model? I have not seen this around???

  29. #29
    *Flashaholic* Mr Happy's Avatar
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    Default Re: Amps vs. Watts vs. Volts?

    Quote Originally Posted by peterharvey73 View Post
    So the 189 has replaced the "179" in the Fluke line up???
    I notice you do have a 179.
    The 189 is a new model? I have not seen this around???
    No, the 289 has replaced the 189 (which is now discontinued).

    The 289 in my opinion is inferior in several respects, being bigger, more battery hungry, and having a more complicated user interface with lots of menus and stuff. Sometimes the march of progress is..."backwards"
    Tiefer, tiefer, irgendwo in der Tiefe gibt es ein Licht

  30. #30
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    Default Re: Amps vs. Watts vs. Volts?

    I got this fluke clamp meter to measure the maximum demand of motors when they start up, it seems to work..only $198...model 374 fluke clamp meter;

    http://www.fluke.com/fluke/usen/elec....htm?PID=70402

    "..proprietary inrush measurement technology to filter out noise and capture motor starting current exactly as the circuit protection sees it.."
    originally cpf member #14 write me at gmail.

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