What is the rating of the bulb?

[TheDanny]

Homework Statement

Given a 24VDC Generator, a 12VDC Battery(Discharged), a bulb(no rating yet), pieces of thick wires(unlimited length you can use)

You need the 24VDC generator to charge the 12VDC battery, but direct will damage the battery. What should I do with the bulb? I need to build a circuit to charge the battery with 24v generator and a bulb is used and what is the rating of the bulb?

The Attempt at a Solution

I tried to fix it parallel but the voltage will be still the same to the battery. What other solution? in figure A.

Figure B. Is the bulb going to light up with both battery same rating 1.5VDC and different rating with 1.5VDC and 4.5VDC.
[PLAIN]http://img837.imageshack.us/img837/3183/63973231.jpg

 

[Stonebridge]

Taking part A
If a parallel circuit doesn't work, what other type of connection should you try?
There are only two ways of connecting the bulb and battery to the generator.

 

[TheDanny]

If I connect it in series, can the light bulb light on and the battery is charging?

 

[Stonebridge]

Yes, no problem. The same current will flow through the bulb as the battery if they are in series. You need to have 12V across the battery, so if the generator supplies 24V, you need half of that across the bulb. Can you see what happens now?

 

[TheDanny]

Ok. That mean Part B if cell A is 3VDC and cell B is 1.5VDC, that mean the bulb will come on and with both 1.5VDC the bulb will remain un-powered because of no potential different?

 

[Stonebridge]

Yes the batteries' will oppose each other, and if they are both the same (1.5V) there is no winner, no potential difference and no current.
If one is 4.5V and the other is 1.5V then yes, there is 3V to power the bulb.

 

[TheDanny]

Thank you for the answer. Then I solved my problems.

I will try it practically.