# The value of q will be negative, therefore

The value of ?AB can be
positive or negative. Positive value means the electromotive force moves the
electric current from the hot junction of metal A to the cooler junction.

The
next thermoelectric effect was found thirteen years later, the Peltier effect. This
effect was observed by J. Peltier. He found that the current passes through
different metals caused the temperature difference at the junction of the
metals. The differential Peltier coefficient, ?AB, is defined as the
ratio between the heating rate of each junction to the applied current:

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(2)

With q is the heating rate and I
is the applied current. The value of ?AB can be written as ?B – ?A, or the difference
between the Peltier coefficient between metal B and metal A. This effect can be
applied for cooling purpose. If  ?B –
?A is negative, the value of q will be negative, therefore heat is
absorbed. This can be explained when ?B