Number of electrons leaving crystal surface. any help ?

AI Thread Summary
The discussion centers on calculating the number of electrons leaving the surface of a crystal based on a measured current of 0.30 pA using a scanning tunneling electron microscope. To find the number of electrons per second, the definition of an Ampere as 1 Coulomb per second is highlighted, along with the conversion factor that 1 Coulomb equals approximately 6.241 x 10^18 elementary charges. Participants clarify the calculation process, leading to the conclusion that the number of electrons is approximately 1,872,000 per second. The conversation reflects a struggle with the underlying concepts but ultimately provides a clear method for arriving at the solution. Understanding the relationship between current, charge, and the number of electrons is essential for solving such problems.
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number of electrons leaving crystal surface. any help :)?

1. A scanning tunnelling electron microscope (STM) measures a tiny electrical current tunnelling out of the surface of a crystal. The current is 0.30 pA (0.30 x 10-12 A).

Calculate the number of electrons per second leaving the surface of the crystal.



2. mass of an electron = 9.11 x 10-31 kg
charge of an electron = -1.6 x 100-19 C



3. I have no idea how to answer this. Thanks to anyone who has any tips or pointers :) or can show me how to work it out correctly! x
 
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CharS said:
1. A scanning tunnelling electron microscope (STM) measures a tiny electrical current tunnelling out of the surface of a crystal. The current is 0.30 pA (0.30 x 10-12 A).

Calculate the number of electrons per second leaving the surface of the crystal.

2. mass of an electron = 9.11 x 10-31 kg
charge of an electron = -1.6 x 100-19 C

3. I have no idea how to answer this. Thanks to anyone who has any tips or pointers :) or can show me how to work it out correctly! x


Welcome to PF.

Neither the mass nor the charge is that useful for this. You need to look at the definition of an Ampere, which is 1 Coulomb/sec.

A Coulomb relates to a quantity of charges. Just look it up and calculate the rest.
Wikipedia said:
A coulomb is then equal to exactly 6.241 509 629 152 65 × 1018 elementary charges.
 


thank you for your help :)

I looked it up before with little success!

so would the answer be = (0.30 x 10^-12) x (6.241 509 629 152 65 × 10^18)

??

i must look incredibly stupid! just never been taught this before, finding it really hard to learn myself x
 


oh wait.

i think it's 0.30 x 10^-12/ 6.24150948×10^18

before was wrong. is that the correct calculation?x
 


CharS said:
thank you for your help :)

I looked it up before with little success!

so would the answer be = (0.30 x 10^-12) x (6.241 509 629 152 65 × 10^18)

When you do the math it will be.

You can simplify the number of digits needed however:

(0.30 x 10-12) x (6.24 × 1018)
 


so the answer is 1,872,000

i'm still struggling to understand how this works. thankyou for your help
 

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