Talk:Potential difference
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I added this equivalent definition which was removed:
- the amount of work that a unit charge that flows from the first point to the second can perform
since I find it more intuitive: one rarely moves a charge from one pole of a battery to the other, but one often exctracts energy from the electrons which flow naturally between the poles. Higher voltage means you get to extract more energy per electron.
In the explanation of emf, I put "force" in quotes, since the emf isn't really a force.
I added information about capacitors and coils and reintroduced the information about transformers that was deleted. AxelBoldt
With apologies to AxelBoldt, I have removed the following paragraphs:
- Since the current I is defined as the amount of charge per time, and potential difference V is energy per charge, the product VI equals energy per time, which is known as power.
- In a capacitor, the potential difference between the two plates is proportional to the charge on the plates; the proportionality constant is the capacitor's capacitance.
- The voltage at the ends of an induction coil is proportional to the time rate of change of the current flowing through the coil, and is directed so as to slow down this change. The proportionality constant is the coil's inductance. By using alternating current and combining two coils of different inductances, it is possible to transform between high and low voltages. These transformers are important in electric power transmission since power losses are minimized if high voltages are used, which are however undesirable in the home.
I think these are better discussed in the individual articles on power, capacitor, inductor and transformer. -- Heron
Removed this line:
- In mechanical systems the potential difference is the velocity difference.
Eh? What?
Potentiometer = potential meter?
Did potentiometer originally refer to a voltmeter? Obviously it doesn't anymore, but someone put it in the article as such, and I read the term in an Isaac Asimov short story as a meter that measured (positronic) voltages. - Omegatron 19:14, Jun 8, 2004 (UTC)
Yes. The original potentiometer was a type of bridge circuit for measuring voltages. The target voltage is connected across a piece of resistance wire, and a standard electrochemical cell of known voltage is then shorted across a variable-length section of the resistance wire using a sliding contact. The contact is moved until no current flows into or out of the standard cell, as indicated by a galvanometer in series with the cell. We then know that the voltage across the selected section of wire is equal to that of the cell. It is then just a matter of calculating the unknown voltage from the cell voltage and the fraction of the resistance wire that was shorted to the cell. The galvanometer does not need to be calibrated, as its only function is to read zero. -- Heron 19:41, 8 Jun 2004 (UTC)