The reference directions of the voltage and of the current are the ones from figure 7.
Figure 7: Signs convention as load
With the reference direction chosen for the voltage, a voltage 
that is positive means that the potential 
of the terminal A is superior to the potential 
of the terminal B. With the reference direction chosen for the current, a current 
that is positive corresponds to the movement of the positive loads from A to B. The potential of the input terminal being superior to the one of the output terminal of the current, the dipole absorbs therefore electrical power.The product 
is therefore positive.
If is positive and is negative, the potential of the input terminal of the current is inferior to the one of the output terminal. The dipole provides electrical power. The product is negative.
If is negative and is positive, the load transfer is made from the terminal with lower potential to the terminal with higher potential. The dipole provides electrical power. The product is negative.
Finally, when both and are negative, the load transfer is made from the terminal with higher potential to the terminal with lower potential. The dipole absorbs electrical power. The product is positive.
With the convention from figure 7, a product 
that is positive, corresponds to a dipole that absorbs electrical power. A product that is negative, corresponds to a supply of electrical power. It is said to be the signs convention as load. This convention is usually chosen for all the dipoles planned to absorb electrical energy (all the passive elements, such as the resistances, the inductances, the capacitors, as well as all the electrical loads: heat resistances, lamps, motors etc.).
