Why Use e.m.f. Instead of Terminal Voltage for Power Calculation?

[Janiceleong26]

1. Homework Statement

Homework Equations

P=IV

The Attempt at a Solution

I used the terminal voltage of battery B, that is I minus the voltage across the internal resistance of battery B from the e.m.f. of battery B, then I multiply it with the current which is 2.5A (calculated earlier) . But it should be just the e.m.f. of battery B multiply the current. Why the e.m.f. and not the terminal p.d.?

 

[mfb]

That's probably a matter of definition of "power transformed by battery B". One calculation gives the power that actually leaves the battery, one gives the power that is required from the energy source within the battery (a part of it will heat the battery).

 

[Janiceleong26]

That's probably a matter of definition of "power transformed by battery B". One calculation gives the power that actually leaves the battery, one gives the power that is required from the energy source within the battery (a part of it will heat the battery).

Got it, thanks