Finding the thickness of graphite in a circuit

  • #1
janegoldberg
1
0
Summary: I have tried everything to understand this but I cant. Please help me.

In class, I "drew a circuit" with a pencil. When the LED was moderately bright about 9mA was flowing and so (since I was using a 9V battery), the resistance was about 1 kΩΩ.
At this point, the distance 𝐿L between the battery and the LED was about 10 cm and the width of the pencil line was about 1cm. If the conductivity of the graphite was about 𝜎𝐶≈1000σC≈1000S/m , estimate the thickness (i.e. height above the paper) of the line I drew.
State your answer in 𝜇μm.
 

Answers and Replies

  • #2
sophiecentaur
Science Advisor
Gold Member
27,835
6,335
Hi. This is clearly a homework problem and it should be posted in the appropriate forum, which you will find at the very top of the list of forums (have a look). There is a pro forma to fill in which requires you to show what work and reading you have already done. Tell us about the "everything" you have tried.
PF doesn't work as a dial a homework answer service but you can get a lot of help if you go about it in the right way.
 
  • #3
berkeman
Mentor
64,166
15,375
Thread moved to the schoolwork forums.

@janegoldberg -- please show your initial try at solving this problem so that we can see where you might need help. Per the PF rules, we can only offer tutorial help after you show your work on the problem. It would also help if you attach a sketch of the "graphite wire" that you are saying is used to attach the LED to the 9V battery. Include the dimensions (the ones you know and the unknown you are supposed to solve for). Thanks.
 

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