Jumping a dead battery in a car

In summary, jumping a dead battery in a car involves using jumper cables to connect the dead battery to a charged one in another vehicle. The positive and negative terminals of both batteries must be matched correctly, and the charged vehicle should be running while the dead one is being jumped. Once the dead battery has enough charge, the cables can be removed and the car should be able to start. It is important to follow safety precautions and consult the vehicle's manual for specific instructions.
  • #1
Eastonc2
20
0

Homework Statement


so the problem, along with the figure, can be found http://www.cramster.com/answers-nov-09/physics/problem-3268-12-car-battery-dies-somuch-volt_697332.aspx?rec=0


Homework Equations


I=V/R,



The Attempt at a Solution



I am able to calculate parts a and b, however, once the batteries are in parallel, I am completely confounded. The concept of the current that would be running through the dead battery completely eludes me.
 
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  • #2
Have you learned to use Kirchhoff's Laws?

That should do it.
 
  • #3
Ok, so, how do I take the second, 'dead', battery into account? I am actually working on a slightly different problem in terms of voltage and resistance, but the arrangement is essentially identical. Do I calculate the current that it would pass through the resistors as well? it's just that when we went over kirchhoffs laws we didn't really cover any instances involving batteries in parallel like this, and it's really throwing me for a loop :wink: lol, get it? sorry bout that last part...
 
  • #4
What I'm trying to find is a break down of the work required. I know how to do the calculations, I am just unsure of how the numbers would work out because of this second battery. I might be approaching this thinking it's more complicated than it actually is, but I see that second battery, the dead one, and don't know what to do with it, and the effect it has on the rest of the circuit.
 
  • #5
You will need voltage equations for two of the three possible loops.

You may need a junction equation, depending upon how you define the currents.
 
  • #6
so, I guess what I'm looking for is, can the dead battery still pass current through the right loop given that the battery on the left is charging it?
 
  • #7
Set up your Kirchoff equations for the loops and your currents in and out of a junction. Just make a guess as to the direction of the current through the second battery if you have no intuition about it. Solve and if you chose the wrong direction you'll get the opposite sign. Once you solve for the currents it should make sense to you.
 
  • #8
Eastonc2 said:
so, I guess what I'm looking for is, can the dead battery still pass current through the right loop given that the battery on the left is charging it?

Yes, it can ... but will current pass through it with this model ? The answer should be interesting.

BTW: What were your answers for (a) and (b) ?
 
  • #9
Set up the equations correctly and you don't have to guess.
 
  • #10
[STRIKE]Well, the bird flies a finite distance, in a finite amount of time, but does that in an infinite number of intervals ![/STRIKE]

OOPS! Wrong thread ! DUH!

Thanks gneill . My computer killed my reply & I jumped to the wrong thread to re-post.
 
Last edited:
  • #11
SammyS said:
Well, the bird flies a finite distance, in a finite amount of time, but does that in an infinite number of intervals !

Well, THAT post was a bit of a train-wreck.
 
  • #12
help on the bird problem just up the list?
 

1. How do I jump start a dead battery in a car?

To jump start a dead battery in a car, you will need a set of jumper cables and another vehicle with a working battery. First, park the two cars close enough so that the jumper cables can reach both batteries. Make sure both cars are turned off and put on the parking brake. Then, attach one of the red clips of the jumper cables to the positive (+) terminal of the dead battery. Next, attach the other red clip to the positive terminal of the working battery. After that, attach one of the black clips to the negative (-) terminal of the working battery. Finally, attach the other black clip to an unpainted metal part of the car with the dead battery, such as a bolt or bracket. Start the working car and let it run for a few minutes. Then, try starting the car with the dead battery. If it doesn't start, let the working car run for a few more minutes before trying again.

2. Can I jump start my car if the battery is completely dead?

Yes, you can jump start your car even if the battery is completely dead. However, it may take longer for the dead battery to charge enough to start the car. If you try to start the car and it doesn't start after a few attempts, you may need to replace the battery.

3. Is it safe to jump start a car in the rain?

It is generally safe to jump start a car in the rain as long as you follow safety precautions. Make sure both cars are turned off and put on the parking brake. Also, make sure the jumper cables are not touching each other or any metal parts of the car. It is also important to avoid getting any water on the battery terminals or jumper cable clamps. If possible, it may be safer to wait until the rain has stopped before attempting to jump start a car.

4. Do I need to replace my car battery after jump starting it?

Jump starting a car does not necessarily mean you need to replace the battery. However, if your car battery has been dead for a while or if it has been jump started multiple times, it may be time for a replacement. It is always a good idea to have your battery checked by a professional to determine if it needs to be replaced.

5. Can I jump start a car by myself?

It is possible to jump start a car by yourself, but it is not recommended. Jump starting a car can be dangerous if not done correctly, and it may be difficult to handle both cars and the jumper cables by yourself. It is best to ask for help from a friend or a professional if you need to jump start your car.

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