If there is two batteries connected in series, each battery is 6V. What is the EMF of the battery?​

The EMF of each battery is 6 volts and the EMF of two batteries connected in series is 12 volts.

Explanation:

According to the Kirchhoff's Voltage Law, net voltage of a closed circuit must be zero. That is:

(1)

Where is the voltage of the i-th component of the closed circuit, measured in volts. Please notice that voltage for a power generating element (i.e. EMF) is less than zero and for a power consuming element is greater than zero (i.e. Batteries being charged by the EMF). In addition, if n-elements are connected in series, then the equivalent voltage is:

(2)

Let consider that closed system is formed by two batteries connected in series and an EMF, by (1) and (2) we have that:

(3)

If we know that , then the EMF of the battery is:

The EMF of each battery is 6 volts and the EMF of two batteries connected in series is 12 volts.