Number of electrons leaving crystal surface. any help ?

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Homework Help Overview

The discussion revolves around calculating the number of electrons leaving the surface of a crystal as measured by a scanning tunneling electron microscope (STM). The problem involves understanding the relationship between electrical current and the flow of charge, specifically in the context of electron charge and current measurement.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the definition of an Ampere and its relation to charge flow. There are attempts to calculate the number of electrons based on the provided current and the charge of an electron. Some participants express uncertainty about their calculations and seek clarification on the process.

Discussion Status

Participants are actively engaging with the problem, sharing their calculations and expressing confusion about the concepts involved. Some guidance has been offered regarding the relationship between current and charge, but there is no explicit consensus on the final answer or method.

Contextual Notes

Some participants mention a lack of prior knowledge on the topic, indicating that they are learning the concepts independently. There is a focus on understanding the definitions and calculations rather than arriving at a definitive solution.

CharS
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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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