Voltmeter Reading?

Question

If i have a 12v battery, and a 6v and 3v bulbs are connected in a circuit...what wud be the reading across each bulb when a voltmeter is connected??

Answer 1

in parallel the voltage drop would be proportional to the resistance.
The bulbs must be 6 and 3 ohms (not volts)
total resistance = 9 ohms
voltage drop and resistance are proportional.
total 9 ohms
across the 6 ohm bulb would be 6/9 * 12 = 8
across the 3 ohm bulb would be 3/9 * 12 = 4

Answer 2

First, you are short information on this one, namely the resistances of the 6v and 3v bulbs.

If you connect the bulbs in parallel, the voltage across them will be 12v, both before and after they burn out.

If you connect them in series they will still burn out, as the combination of resistances will not be enough to limit the current the battery can supply. After the 6v bulb burns out, the voltage across each will be 0.

A reasonable assumption is that both bulb filaments heat to the same temperature when connected to their rated voltages. Then
6^2/R = 3^2/r and
R/r = 4, so
12 = i(R + r) = i(r + 4r) = 5ir
then
V(6) = iR = (12/5)(R/r) = 4*12/5 = 9.6v
V(3) = ir = (12/5)(r/r) = 12/5 = 2.4v
9.6 + 2.4 = 12.0

(9.6/6)^2 = 2.56 times the rated capacity of the 6v bulb