# Two batteries with inner resistor in parallel

• lalallaland
In summary, two batteries, A and B, with e.m.f values of 100V and 95V and internal resistance values of 5ohms and 3ohms respectively, are connected in parallel. An 80 ohm resistor is connected across the battery terminals. The task is to calculate the value and direction of the current in each battery. After setting up the KVL equation, it was determined that the current in each battery is 1.183, and the batteries are not truly connected in parallel.
lalallaland
Homework Statement
two batteries A and B are connected in parallel, and an 80 ohm resistor is connected across the battery terminals. the e.m.f and the internal resistance of battery A are 100V and 5ohms respectively, and the corresponding values for battery B are 95V and 3ohms respectively.
Relevant Equations
Calculate the value and direction of the current in each battery.
I am kind of stuck at this exercise and I would like some help.

Thanks a lot!

lalallaland said:
Homework Statement: two batteries A and B are connected in parallel, and an 80 ohm resistor is connected across the battery terminals. the e.m.f and the internal resistance of battery A are 100V and 5ohms respectively, and the corresponding values for battery B are 95V and 3ohms respectively.
Homework Equations: Calculate the value and direction of the current in each battery.

I am kind of stuck at this exercise and I would like some help.

Thanks a lot!
Please draw the circuit and show us how you would set up the KCL equations. Thanks

Hi berkeman,

I started to calculate the terminal voltage, cause I thought that might help.
v= terminal voltage

(v/80) + (v-100)/5 + (v-95)/3 =0

v=94.66 V

with that, I calculated the current across the 80 ohm resistor:

I=v/R = 94.66/80 = 1.183

From the answer sheet, I know that this is correct as it is the sum of the individual currents in each battery.
But I do not know how to calculate it. I tried using the current divider rule, but it doesn't work.

#### Attachments

• batteries in parallel.pdf
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Ah, sorry, the drawing helps a lot. I thought the resistor was in parallel with the mismatched batteries, so that's why I asked for the KCL equation(s).

Since it is just one loop per the figure, a KVL equation is the better fit. Can you write that equation to see if it helps? The current around the loop through the various components is the same, right?

lalallaland said:
Homework Statement: two batteries A and B are connected in parallel
As has been pointed out, they are then NOT in parallel. This is not just semantics. It is important to use proper terminology in science.

berkeman

## 1. What is the purpose of having two batteries with inner resistor in parallel?

Having two batteries with inner resistor in parallel allows for a more efficient and reliable power source. By connecting the batteries in parallel, the overall voltage remains the same while increasing the total current capacity. The inner resistors also help to balance the load and prevent one battery from draining faster than the other.

## 2. How do the inner resistors affect the overall performance of the batteries?

The inner resistors in the batteries help to regulate the flow of current and prevent overloading. They also help to maintain a stable voltage output, ensuring that the batteries do not overheat or become damaged. The overall performance of the batteries is improved by having these inner resistors in place.

## 3. Can I mix different types of batteries with inner resistors in parallel?

It is generally not recommended to mix different types of batteries in parallel, especially if they have different inner resistors. This can lead to imbalances in voltage and current, and may cause damage to the batteries. It is best to use batteries of the same type and specifications when connecting them in parallel.

## 4. How does connecting batteries with inner resistors in parallel affect the overall circuit?

Connecting batteries with inner resistors in parallel affects the overall circuit by increasing its total current capacity. This means that the circuit can handle more devices or components without overloading. However, it is important to ensure that the total voltage and current of the batteries are within the limits of the circuit.

## 5. Are there any safety precautions I should take when using batteries with inner resistors in parallel?

Yes, there are a few safety precautions to keep in mind when using batteries with inner resistors in parallel. It is important to use batteries of the same type and specifications, and to ensure that the total voltage and current do not exceed the limits of the circuit. Additionally, it is recommended to use a fuse or circuit breaker to prevent overloading and potential hazards.

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