Calculating A-hrs: Understanding a Car Battery's Performance and Efficiency

  • Thread starter Thread starter nckaytee
  • Start date Start date
  • Tags Tags
    Calculation
Click For Summary

Homework Help Overview

The discussion revolves around calculating the duration a car battery rated at 70 A-hrs can last when operating at a current of 15 A. Participants are exploring the relationship between amp-hours and time, as well as the conversion of units involved in the calculation.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants present different methods for calculating the time duration, including direct division of amp-hours by current. Some raise questions about the conversion to coulombs and the implications of these conversions on the final answer.

Discussion Status

The discussion includes various interpretations of the problem, with some participants questioning the calculations and assumptions made. There is no explicit consensus on the correct approach or final answer, but guidance is being offered regarding unit conversions and the relationships between the quantities involved.

Contextual Notes

Participants are working with a practice exam context, which may impose constraints on the methods they can use. There is also a focus on ensuring understanding of the underlying principles rather than simply arriving at a numerical answer.

nckaytee
Messages
39
Reaction score
0
My teacher posted a practice exam with no answers so I want to make sure I am doing my problems right.

A car battery is rated at 70 A-hrs. How many minutes can this battery last if it operates at a current of 15A?

I made an equation 70A/60min = Xmin/15A

So, X=17.5 min

Am I right?
 
Physics news on Phys.org


nckaytee said:
My teacher posted a practice exam with no answers so I want to make sure I am doing my problems right.

A car battery is rated at 70 A-hrs. How many minutes can this battery last if it operates at a current of 15A?

I made an equation 70A/60min = Xmin/15A

So, X=17.5 min

Am I right?

An amp is one coulombs per sec. That means that an Amp hour is 3600 coulombs.

70 amp hours is 252,000 coulombs.

15 amps is 15 coulombs per sec = 54,000 coulombs in an hour.
 


so 900 minutes?
 


nckaytee said:
so 900 minutes?

How did you get 900 minutes?

You have 252,000 coulombs to spend and you spend 54,000 an hour? How many hours is that again? Times how many minutes an hour?
 


Just divide 70 A-h by the 15 A, the A cross themselves out and your left with just the hours not necessary to switch to coulombs.
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 5 ·
Replies
5
Views
5K
  • · Replies 6 ·
Replies
6
Views
7K
Replies
10
Views
6K
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 3 ·
Replies
3
Views
4K
Replies
54
Views
12K
Replies
0
Views
2K