I'm also having some trouble with this. I've attached a schematic of three questions that I am struggling with. I have to find the voltage of these three arrangements and as far as I can see, none of them would work or be safe. Each cell is 1.5v.

Any help would really be appreciated.

Thanks.

 

Hello,

You just hyjacked an old existing thread:
different batteries in parallel

As this is not allowed over here I moved it to its own thread.

What have you done to solve the problem?

Bertus

 

Hi,
Sorry about that. Pretty new here!

I don't know how to go about working it out. I'm unsure as to whether the voltage would average across the two different sized sources or if the higher voltage would be the dominant.

With the first two drawings, I can't see how they would give any voltage at all.

 

Hello,

Take a close look at the schematics:

For the circuits 1 and 2:
Take a reference point.
Look good at the directions of the cells.
If the cell is in forward direction, add the value.
If the cell is in the opposite direction, subtract the value.

Bertus

 

4.5 Volts?

 

Do as bertus suggested. I've annotated the first two with node labels. Start at one end and call that node 0V. Then write the voltage at each node as you go.

For the third one, pick one of the common points (i.e., the left or right wire) as the 0V node. Then label the voltage at the other side of the top battery and label the voltage at the other side of the bottom battery. Now consider that you will have two different voltages connected by a wire. If we are talking about ideal batteries and ideal wires, how much current would flow?

As to your original suspicion that the arrangments are unsafe, the answer is yes and no for the first two and yes for the third. If current flows "backwards" in a battery, it is being charged. While an ideal battery has no problem with this, many real batteries do not tolerate this well and can leak, catch fire, or explode.