1. Dec 10, 2012

### a_patel32

1. The problem statement, all variables and given/known data

A current of 20 amperes is being drawn from a battery whose emf is 24 volts. The
internal resistance of the battery is 0.3 ohms. By how many volts is the battery "loaded
down"?

2. Relevant equations

V = IR

3. The attempt at a solution I dont know what it means for the battery to be loaded down? Try searching for it but could not find anything. Please advice.

2. Dec 10, 2012

### Staff: Mentor

Granted, "loaded down" is an inexact (perhaps colloquial) expression. In this case it refers to the amount by which the emf presented at the battery's terminals has fallen below its rated value.

3. Dec 10, 2012

### a_patel32

Oh so after a battery has been used?

4. Dec 10, 2012

### Staff: Mentor

No, while it is being used.

5. Dec 10, 2012

### a_patel32

Okay, I'm still unsure of how to solve this but I understand what you are saying so far, i think.

6. Dec 10, 2012

### Dick

I'm kind of curious here. How much the emf at the terminals is below the rated value depends on what load you put on the battery right? So the "loaded down" voltage will be a function of the load resistance, right? Not a single number?

7. Dec 10, 2012

### Staff: Mentor

Indeed. Which is why the question asks, 'By how many volts is the battery "loaded
down"?' given a load drawing 20 A.

Last edited: Dec 10, 2012
8. Dec 10, 2012

### Staff: Mentor

You have a 24V ideal voltage supply in series with 0.3 Ohms inside a box labelled "24V Battery". If a load that draws 20A is connected to this battery, what voltage will you "see" at the battery's terminals?

9. Dec 10, 2012

### Curious3141

Is it necessary to calculate that? If "load down" refers to the amount by which the "usable" voltage has fallen, then they don't even need to provide the EMF of the cell, right? (given that they already stated the internal resistance and the current drawn)

10. Dec 10, 2012

### Dick

Ooops. I missed that they gave you the current. Duh. Sorry. Carry on.

11. Dec 10, 2012