Re: why does a battery heat up when conected to negitive and positive.

We will analyze the fact that "batteries heat up when connected to negative 
and positive" in two part: electrotechnics and chemistry.

Electrotechnics :
A battery is a power source. It means, it has a potential voltage with
an almost constant value of voltage V (e.g. 1,5 volts). When connected
to a circuit, it emits electrical current I, where I = V/R, and R
is total resistance of the circuit.

A wire is a good conductor. It has a very little resistance. When a circuit
contains only a wire, it has a very litthe value of R. While V is constant,
and R is very little, the value I = V/R would be very large.

The physical form of 'current' is electrons moveing throught the circuit.
Large value of I means that a very large amount of electron are moving
throught the circuit, including the battery. And the kinetic energy
of large amount of electrons through the wire and the battery forms
'heat'.


Chemistry :

The battery itself is a chemical element, with its own anode (positive
pole) and cathode (negative pole). When the anode and cathode connected
directly, the chemical reaction happens. This is endothermic reaction
that emits energy. Heat is the main form of energy emitted.