# Ideal Batteries' Internal Resistance

• LowerMammal
In summary, a circuit with five resistors and an ideal battery with an internal resistance has been constructed. The values for the resistors are given and the measured voltage across the battery terminals is known. Using the potential divider equation, the internal resistance of the battery can be calculated by dividing the total external resistance by the amperage.
LowerMammal

## Homework Statement

A circuit is constructed with five resistors and one real battery as shown above right. We model. The real battery as an ideal emf V = 12 V in series with an internal resistance r as shown above left. The values for the resistors are: R1 = R3 = 59 Ω, R4 = R5 = 79 Ω and R2 = 140 Ω. The measured voltage across the terminals of the batery is Vbattery = 11.61 V.
What is r, the internal resistance of the battery?

## Homework Equations

Vb = Vo((R/r)/(1+R/r))
Vb= voltage across battery terminals
Vo= Internal voltage
r= internal resistance
R= external resistance
Total ext. resistance in parallel: 1/Rt= 1/r1 + 1/r2
total ext. resistance in series: Rt = r1 + r2

## The Attempt at a Solution

Taking total resistance dividing by the amperage.

No figure attached.

Taking total resistance dividing by the amperage.

That would just give you the ideal voltage which is already known.

Hint: Potential divider

## 1. What is internal resistance in batteries?

Internal resistance in batteries refers to the resistance within the battery itself that limits the flow of electric current. It is caused by the materials used in the battery and the chemical reactions that take place within it.

## 2. Why is internal resistance important in batteries?

Internal resistance affects the performance and efficiency of a battery. It can cause voltage drops and reduce the amount of usable energy that the battery can provide. In high drain applications, a battery with low internal resistance is necessary for optimal performance.

## 3. How does internal resistance affect battery life?

High internal resistance can lead to increased heat and stress within the battery, which can decrease its lifespan. It can also cause self-discharge and reduce the amount of energy that can be stored in the battery.

## 4. Can internal resistance be reduced in batteries?

Internal resistance is inherent to the materials and design of the battery, so it cannot be completely eliminated. However, it can be reduced by using high-quality materials, efficient designs, and proper manufacturing processes.

## 5. How can internal resistance be measured in batteries?

Internal resistance can be measured by using a multimeter and performing a voltage drop test. This involves measuring the voltage of the battery under load and calculating the internal resistance using Ohm's Law (R = V/I).

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