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The proof of this is a little more difficult than the first term; more details and alternate approaches for the proof can be found in the references. [ 28 ] [ 29 ] [ 30 ] As the loop moves and/or deforms, it sweeps out a surface (see the right figure).
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections [1] for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. [2] The terminal marked negative is the source of electrons.
The term on the left is the rate of change of the charge density ρ at a point. The term on the right is the divergence of the current density J at the same point. The equation equates these two factors, which says that the only way for the charge density at a point to change is for a current of charge to flow into or out of the point.
Inside a source of emf (such as a battery) that is open-circuited, a charge separation occurs between the negative terminal N and the positive terminal P. This leads to an electrostatic field E o p e n c i r c u i t {\displaystyle {\boldsymbol {E}}_{\mathrm {open\ circuit} }} that points from P to N , whereas the emf of the source must be able ...
A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers ...
Franklin called this device an "electrical battery", [4] but that term later came to have a different meaning, referring instead to a set of one or more galvanic cells. At that time, the word "battery" was a military term for a group of cannons. [32] Franklin was the first to apply the terms "positive" and "negative" to electricity.
However, if the value assigned to E ea is negative, the negative sign implies a reversal of direction, and energy is required to attach an electron. In this case, the electron capture is an endothermic process and the relationship, E ea = −ΔE(attach) is still valid. Negative values typically arise for the capture of a second electron, but ...
Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode.