# ohms law

Discussion in 'Tech/Mech General' started by betterthenatent, Mar 19, 2011.

1. ### betterthenatent

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Can anyone refresh my memory on ohms law. We are having our first trip of the year next week and I thought I might take a 1-2 w fan heater will this be OK on a hook up. A few examples would help.

2. ### MunchieFunsterLife Member

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OHMS law states that the current flowing in any conductor is directly proportional to the EMF and inversley proportional to the resistance providing the temperature remains constant.

If my memory hasn't failed me.

3. ### peter HFunsterLife Member

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Power (watts) = Volts X Amps

or

Amps = Watts / Volts

so

2000 watts / 240 volts = 8 amps approx

4. ### callumwa

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P = I x V

Power (P) in watts = (I) current in Amps x (V) Voltage in Volts

1 Kw rated heater is 1000 watts, so at 240 volts is drawing approx 4amps....

2Kw (2000 watts) drawing approx 8 amps... and so on..

5. ### betterthenatent

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Thanks for the replies. I sort of had an idea that was it but some how I thought a 1kw appliance would draw more currant.

6. ### rainbow chasers

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ohms law = oh my god, the whole site has gone out!

7. ### lunarmanFunsterLife Member

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Not wishing to be pedantic but ohms law makes does no reference to power.

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them.

The mathematical equation that describes this relationship is: I = V/R

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.

8. ### Simannjo

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Ohms law = have on what you want untill the post trips...

9. ### bigfootFunster

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Ohm sweet ohm

10. ### GromettFunster

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Draw a triangle on a piece of paper. Put the letter V at the top.
Put an I at the bottom left and an R at the bottom right.

Cover the one you want to find out with your finger and what is left is the formula.

For example you want to know what V is. The answer is IR
You want to know what I is. The answer V over R (V/R)

Power is Current X Voltage. Using ohms law and transposition of the above formulas you can work out.

W = I2R (I Squared x R)
W = IV
W = V2/R (V Squared over R)

There are 12 formulae in total using these 4 variables.

Bear in mind though that these only apply to resistive loads only. When you get into capacitive and Inductive loads you have to take Xc and Xl into account. These are Inductive Reactance and Capacitive Reactance but don't worry too much about these if doing rough and ready calcs for cabling etc.

However when working on 12V car gear, remember that the voltage can be as high as 14.4V when working out current flow in cables.

Karl

11. ### GromettFunster

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W = IV.
Tranposed
I = W/V

Quick a rough way I use is each 1KW is 4 Amps. Not totally accurate but close enough for checking if a breaker will cope with a 1KW heater etc.

Karl

12. ### dave newell lvsTrader-Vehicle Services

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You're not going to get much heat out of a 1-2 watt heaterr though.

D.

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14. ### DBSilverfox

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When I was at school they taught us to remember it as the girl's name - Ivy Watts. (I x V = Watts), and use the triangle trick.

Always stuck.

David

15. ### gollyFunster

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Don,t forget when calculating your total Amps to take account of the battery charger and fridge etc. I have a card with the amps used by each appliance I use, then I know if I have to switch anything off before putting say the kettle on. Sad I know but better than tripping the post or even the site supply.

John

16. ### scotjimlandFunsterLife Member

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Now that's been done... :thumb:

could someone explain E=mc2 (in laymen's terms)

Karl ?

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Not sure on the fine details, but it has to do wit Museums:thumb:
Ohm is where the art is:Cool:

18. ### Wildman

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there you go.

where E is energy, m is mass, and c is the speed of light in a vacuum. The formula is dimensionally consistent and does not depend on any specific system of measurement units. For example, in many systems of natural units, the speed (scalar) of light is set equal to 1 ('distance'/'time'), and the formula becomes the identity E = m'('distance'2/'time'2)'; hence the term "mass–energy equivalence

19. ### TerryFunsterLife Member

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That sounds a good idea to me :thumb:Plug it in -if it works its OK
terry

20. ### scotjimlandFunsterLife Member

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that's not Ohms law... that's Murphy's law oh: