# Magnitude of the current in a battery

• nickm
In summary, Kirchoff's junction & loop laws states that the current through a junction or loop is the sum of the currents through the individual loops. The Attempt at a Solution was trying to find the current in a battery in a multi-loop circuit, but couldn't find a solution. After figuring out that the current had to be positive, the student was able to solve the problem.
nickm

## Homework Statement

Find the magnitude of the current in the 14V cell.

## Homework Equations

Kirchoff's junction & loop laws:
I1 = I2 + I3

ƩΔV = 0

V = IR

Rseries = R1 + R2 + ...

1/Rparallel = 1/R1 + 1/R2 + ...

## The Attempt at a Solution

At first I assumed that the current inside an ideal battery is 0 amps. But it appears that is incorrect. I've been going over my notes and looking through my book for a while now, but I have had no luck in finding out how to find the current in a battery in a multi-loop circuit. I have also tried setting up 2 different loop equations but those were wrong too. I know that the value has to be positive because it wants the magnitude. I'm not going to give up on this but I do need help from a reliable source. Any help is welcome.

nickm said:

## Homework Statement

Find the magnitude of the current in the 14V cell.

## Homework Equations

Kirchoff's junction & loop laws:
I1 = I2 + I3

ƩΔV = 0

V = IR

Rseries = R1 + R2 + ...

1/Rparallel = 1/R1 + 1/R2 + ...

## The Attempt at a Solution

At first I assumed that the current inside an ideal battery is 0 amps. But it appears that is incorrect. I've been going over my notes and looking through my book for a while now, but I have had no luck in finding out how to find the current in a battery in a multi-loop circuit. I have also tried setting up 2 different loop equations but those were wrong too. I know that the value has to be positive because it wants the magnitude. I'm not going to give up on this but I do need help from a reliable source. Any help is welcome.

How do you know your "2 different loop equations" were wrong?

Also, in the context of this problem, I'm 98.3% positive that "1/Rparallel = 1/R1 + 1/R2 + ..." is irrelevant.

What I had done was Loop 1 being the circuit containing the 14 V battery and the 29V battery. Setting up the equation 12I2 - 23I1 = -43 for the top loop and 12I1 - 27I2 = -66 for the bottom loop. Then I put together a system of equations. I multiplied the top loop equation by 9 and the bottom by 4 so that the I2 would cancel. This gave me the value of I1 to be about 4.094 amps. Knowing that the current in a series of resistors is equal to each other, I had assumed that the battery was some sort of resistor so I had put that answer down and the system showed to be wrong.

Also, thanks for the quick response!

nickm said:
What I had done was Loop 1 being the circuit containing the 14 V battery and the 29V battery. Setting up the equation 12I2 - 23I1 = -43 for the top loop and 12I1 - 27I2 = -66 for the bottom loop. Then I put together a system of equations. I multiplied the top loop equation by 9 and the bottom by 4 so that the I2 would cancel. This gave me the value of I1 to be about 4.094 amps. Knowing that the current in a series of resistors is equal to each other, I had assumed that the battery was some sort of resistor so I had put that answer down and the system showed to be wrong.

Also, thanks for the quick response!

Ah. When you went around your loops and summed the voltage supplies, you didn't take into account the fact that you're passing through one going from positive to negative, and the other negative to positive.

Gah, it is always the little mistakes! Thank you so much, I finally got it! :D

## 1. What is the magnitude of the current in a battery?

The magnitude of the current in a battery refers to the strength or intensity of the flow of electric charge through the battery. It is typically measured in amperes (A) and can vary depending on factors such as the type of battery, its age, and the load connected to it.

## 2. How is the magnitude of the current in a battery determined?

The magnitude of the current in a battery is determined by the difference in potential (voltage) between the positive and negative terminals of the battery, as well as the resistance of the circuit. This is described by Ohm's Law: I = V/R, where I is the current in amperes, V is the voltage in volts, and R is the resistance in ohms.

## 3. Can the magnitude of the current in a battery be changed?

Yes, the magnitude of the current in a battery can be changed by altering the voltage or resistance in the circuit. For example, increasing the voltage or decreasing the resistance will result in a larger current, while decreasing the voltage or increasing the resistance will result in a smaller current.

## 4. What happens if the magnitude of the current in a battery is too high?

If the magnitude of the current in a battery is too high, it can cause the battery to overheat and potentially damage it. This is because a high current can lead to excessive heat generation, which can degrade the battery's components and decrease its lifespan.

## 5. How does the magnitude of the current in a battery affect its lifespan?

The magnitude of the current in a battery can have a significant impact on its lifespan. A higher current can lead to increased heat generation, which can accelerate the chemical reactions within the battery and shorten its lifespan. It is important to use the appropriate current for the specific type of battery to ensure its longevity.

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