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Rayengine
Joined: 18 May 2001
Posts: 314
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 05 Dec 2003 11:19 What is EMF? |
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Dear All,
I always found a unit (EMF) in RF Signal Generator, IC specification, but I don't know the exact meaning of the figures. How is unit related to common unit likes dBuV and dBm. Please help!
BR
Rayengine
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Beepster
Joined: 21 Jul 2001
Posts: 139
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| 05 Dec 2003 16:21 |
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| EMF may be ( electro motive force ) or "volts"
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flatulent
Joined: 19 Jul 2002
Posts: 4856
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Location: Middle Earth
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| 05 Dec 2003 18:07 Re: What is EMF? |
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| It does stand for electromotive force which is measured in volts. For some reason people like to say volts instead of emf although they say current and not amps.
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ME
Joined: 14 Mar 2002
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| 05 Dec 2003 18:14 |
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Most people say voltage, which is measured in volts.
Voltage and volts is not the same.
Just like current and amps is not the same.
Both EMF and Voltage are measured in volts.
EMF is the voltage without the voltage drop from the internal ouput resistance of the signal generator.
Therefore the real output voltage is always lower than the EMF.
The output voltage changes with changing current draw. The EMF never changes.
Only when you draw no current, the output voltage is as high as the EMF.
If your signal generator has an output resistance of for example 50 ohms, then you can calculate the output voltage if you know the EMF and the current.
Please read this document:
http://www.korins.co.kr/m/fourier/support/Physics/electricity%20and%20magnetism/EMF-%20Voltage%20and%20Internal%20Resistance.pdf
| Quote: |
The potential difference between the terminals of a voltage source when it is not
connected to an external circuit is the electromotive force (E.M.F) of that source. The
symbol ε will be used for the electromotive force. When an external circuit is
connected to the source the potential difference V between the terminals will drop
below its open circuit value. The difference between ε and V is caused by the
internal resistance r of the source. The value of V will be:
V Ir = − ε
where Ι is the current through the external circuit. |
Another link:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 05 Dec 2003 19:03 Re: What is EMF? |
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In physics type things like electromagnetic field theory, the line integral of the electric field is called emf and measured in volts.
In circuits text books from 75 or more years ago, ideal voltage generators used in the circuit analysis examples were labeled as having an emf of so many volts.
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