Point me in the right direction

In summary, the conversation discusses a problem involving a storm cloud with a potential difference of 1.00 X 10^8 V and a tree. The problem also involves the transfer of 50.0 C of charge and the absorption of 1.00% of energy by the tree. The question asks how much water can be boiled away, given that the water has a specific heat of 4186 j /kg * degrees Celsius, a boiling point of 100 degrees Celsius, and a heat of vaporization of 2.26 X 10^6 J /kg. The conversation also touches on the topic of energy stored in a capacitor and the use of equations to solve the problem. It is noted that the conversation is
  • #1
jpnnngtn
Here's the problem:

A certain storm cloud has a potential difference of 1.00 X 10^8 V relative to a tree. If, during a lightning storm, 50.0 C of charge is transferred through this potential difference and 1.00% of the energy is absorbed by the tree, how much water (sap in the tree) initially at 30 degrees Celsius can be boiled away? Water has a specific heat of 4186 j /kg * degrees Celsius. It has a boiling point of 100 degrees Celsius, and a heat of vaporization of 2.26 X 10^6 J /kg


I know that this problem has to do with Energy stored in a capacitor.

Potential Difference = 1.00 X 10^8


C = e(o)(A / d) "I don't have an area or a distance so that wouldn't matter"

I think what is throwing me off is the temperature included in this problem, for that matter, everything involving the water.
 
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  • #2
Originally posted by jpnnngtn
Here's the problem:

A certain storm cloud has a potential difference of 1.00 X 10^8 V relative to a tree. If, during a lightning storm, 50.0 C of charge is transferred through this potential difference and 1.00% of the energy is absorbed by the tree, how much water (sap in the tree) initially at 30 degrees Celsius can be boiled away? Water has a specific heat of 4186 j /kg * degrees Celsius. It has a boiling point of 100 degrees Celsius, and a heat of vaporization of 2.26 X 10^6 J /kg


I know that this problem has to do with Energy stored in a capacitor.

Potential Difference = 1.00 X 10^8


C = e(o)(A / d) "I don't have an area or a distance so that wouldn't matter"

I think what is throwing me off is the temperature included in this problem, for that matter, everything involving the water.

I don't think it is the temperature so much as the "area-distance" problem. It's interesting that you give a formula that involves area and distance and then say "I don't have an area or a distance so that wouldn't matter"! What you really mean is that that formula is irrelevant.

The crucial point is that a "volt" is a measure of potential difference per coulomb. Since you are told that the lightning had a voltage of 1.00 X 10^8 V and the tree was hit by 50 Coulombs, there was an energy increase of 50 X 10^8 Joules.

Now, use the temperature information.

You know that the specific heat of water is 4186 j /kg * degrees Celsius so it takes 70* 4186= 293020 J to raise each kg of water from 30 to 100 degrees C. That is, if the mass of water is M, The energy required to raise it to 100 degrees C is 293020*M Joules which is
2.93 X 10^5*M Joules (3 significant figures since heat of vaporization is only given to 3 significant figures).
You also know that the "heat of vaporization" for water is 2.26 X 10^6 J /kg so the amount of energy necessary to vaporize M kg. of water is 2.25 X 10^6 *M= 22.5 X 10^5 *M Joules.

To raise M kg of water from 30 degrees to 100 degrees and then vaporize it requires: 2.93 X 10^5*M+ 22.5 X 10^5*M =
25.4 X 10^5*M Joules. Since you know the total Joules available is
50 X 10^8 Joules. Solve for M.
 
  • #3
Remember that electrical energy equals Vq

You know V and you know q

solve for EPE

find one percent of this

Look in a first semester physics book to find equations you can plug into solve for the rest.
 
  • #4
And this is college level? During which year of college do you touch QFT, QED, QCD, Group Theory or Representations?
 
  • #5
It depends on what college it is...because they learn many different things...not necessarily at the highest level...
I saw a paper about artificial neural nets for students who were studying something completely different...
 
  • #6
This is much to juicy to discuss here. I'll open a thread about what classes does each of us take.

P.S. It's funny to see two romanians talking in english.
 

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To get a helpful response, it is important to be specific about what you need guidance on and to also express gratitude for any help given. For example, "Can you please point me in the right direction for finding reliable sources for my research? Thank you for your assistance!"

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