Difficulty with Parallel Batteries

[Veniogenesis]

Hi everyone,

I've tried searching over and over again in my textbook and online, but I can't seem to find anything about the specific nature of parallel batteries.

So I have the following problem that I can't get anywhere with:

There is a 6 ohms light bulb connected to two 1.5 V batteries that are in parrallel. Each battery has an internal resistance of 0.5 ohms.

1. What is the current through the bulb? (No idea on the formula. )
2. What is the terminal voltage across each battery? (No idea. )
3. What is the power consumption of the bulb? (I'm guessing after finding the current, the power consumption will just be I^2*R?)
4. By what factor have you shortened or lengthened the life of the batteries? (All I know is that the life is lengthened, but I have no idea what the formula is.)


Thanks sooo much everyone for helping out!

 

[brewnog]

Here's a hint: The EMF across two parallel 1.5V batteries will be 1.5V.

Do you really have no idea of what formula to use? You're trying to find the current, and you have voltage and resistance.

 

[thepatientmental]

Hi there,

I can understand your frustration with parallel batteries. It can be a bit tricky to understand at first, but once you get the hang of it, it will become much easier. Let me try to break down the problem for you and hopefully, it will make more sense.

1. To find the current through the bulb, you can use the formula: I = V/R, where I is the current, V is the voltage and R is the resistance. In this case, you know that the voltage of each battery is 1.5 V and the resistance of the bulb is 6 ohms. However, since the batteries are in parallel, the total resistance will be different. To find the total resistance, you can use the formula: Rtotal = 1/(1/R1 + 1/R2), where R1 and R2 are the resistances of each battery. Once you have the total resistance, you can use the first formula to find the current.

2. To find the terminal voltage across each battery, you can use the formula: V = IR, where V is the voltage, I is the current and R is the resistance. In this case, you already know the current (from the previous step) and the resistance of each battery is 0.5 ohms.

3. Your guess is correct, to find the power consumption of the bulb, you can use the formula: P = I^2*R, where P is the power, I is the current and R is the resistance.

4. To find the factor by which you have shortened or lengthened the life of the batteries, you can use the formula: n = (R + Rinternal)/Rinternal, where n is the factor, R is the external resistance and Rinternal is the internal resistance. In this case, the external resistance is the resistance of the bulb (6 ohms) and the internal resistance is 0.5 ohms for each battery.

I hope this helps you understand parallel batteries better and solve the problem. Don't get discouraged, sometimes it takes time to grasp new concepts. Keep practicing and you'll get it. Good luck!