# Calculating Battery Internal Resistance: V=IR Method

• accol
In summary, the conversation discusses a battery with an emf of 24V and terminal voltage of 22V when connected to a 7.5ohm resistor. The internal resistance of the battery is found to be .68ohm, but the process to reach this answer is unclear. The questions asked are about the voltage drop across the internal resistance, the current through the circuit, and how to combine these two answers to find the internal resistance.
accol
1. A battery is manufactured to have and emf of 24V, but the terminal voltage is only 22V when the battery is connected across a 7.5ohm resistor...what is the internal resistance of the battery?

3. Ok I have the answer already which is .68ohm...but I can't find a way to get to it. At first I tried V=IR or 24=I*7.5 and then plugged that answer into the same equation but with the voltage of 22. I also tried the opposite way. That answer didn't work.

I also tried subtracting the volts from each other to get .27R. Can someone please tell me what I am doing wrong?

What's the voltage drop across the internal resistance?
What's the current through the circuit?
Combine these two answers to find the internal resistance.

I would first like to commend you for attempting to solve this problem and seeking help when you encountered difficulties. It shows a strong critical thinking mindset and a willingness to learn.

Now, let's go through the steps to solve this problem using the V=IR method.

First, we need to understand the equation V=IR. This equation means that the voltage (V) across a resistor is equal to the current (I) flowing through the resistor multiplied by the resistance (R) of the resistor.

In this problem, we are given the emf (electromotive force) of the battery, which is the maximum potential difference it can provide. This value is 24V. However, when the battery is connected to a 7.5ohm resistor, the terminal voltage is only 22V. This means that there is a voltage drop of 2V across the resistor.

Using the V=IR equation, we can set up the following equation:

22V = I * 7.5ohm

Now, we need to solve for the current (I) flowing through the resistor. To do this, we divide both sides of the equation by 7.5ohm. This gives us:

I = 22V / 7.5ohm

Simplifying this, we get I = 2.93A. This means that there is a current of 2.93A flowing through the resistor.

Now, we can use this current value and the given voltage drop of 2V to calculate the internal resistance of the battery. We can rearrange the V=IR equation to solve for R, which gives us:

R = V / I

Substituting the values, we get R = 2V / 2.93A. Simplifying this, we get R = 0.68ohm. This is the internal resistance of the battery.

In summary, to calculate the internal resistance of the battery using the V=IR method, we need to first identify the voltage drop across the resistor, calculate the current flowing through the resistor, and then use these values to solve for the internal resistance. I hope this explanation helps you understand the problem and the steps to solve it. Keep up the good work!

## 1. What is the purpose of calculating battery internal resistance using the V=IR method?

The V=IR method is used to determine the internal resistance of a battery, which is important for understanding its overall performance and efficiency. It can also help identify any potential issues or deterioration in the battery.

## 2. How is the V=IR method used to calculate battery internal resistance?

This method involves measuring the voltage (V) and current (I) of the battery while it is under load, then using the equation R=V/I to calculate the internal resistance (R) of the battery.

## 3. What factors can affect the accuracy of the V=IR method?

The accuracy of this method can be affected by factors such as the accuracy of the voltage and current measurements, the temperature of the battery, and the type and condition of the load applied.

## 4. Can the V=IR method be used for all types of batteries?

While the V=IR method can be used for most types of batteries, it may not be suitable for batteries with very low internal resistance or for batteries that cannot handle a load. In these cases, alternative methods may be more appropriate.

## 5. What are some potential applications of knowing a battery's internal resistance?

Knowing a battery's internal resistance can help in determining its overall health and predicting its remaining lifespan. It can also be useful in designing and optimizing battery-powered systems, such as in electric vehicles or renewable energy systems.

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