Resistors make horrible voltage regulators, why are you using a battery like that? The whole idea screams 'bad' to me. If you want a variable voltage source buy a variable voltage regulator IC a pot to control the voltage and a few caps for the input and output, and feed it from a 12V DC wallwart supply.
Even if your load is a static one like a bulb or a small motor using a resistor for 1.5 volts will waste over 90% of the power from the battery directly as heat, the battery would hardly last long enough to be useful, and the run time from that 12V is probably a little worse than a 9volt battery, meaning pitifully short.