Alkaline batteries have the advantage of putting out constant voltage until very nearly the end of their life. How long will an alkaline battery rated at 1 A ⋅ h and 1.58 V keep a 1 W flashlight bulb burning?

Answer 1

P = E*I = 1.0 W.
1.58I = 1.0
I = 0.633A.

A*h = 1.
0.633*h = 1.
h = 1.58 Hours.

Answer 2

MITA VITTUA