Just wondering about electrons.

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Homework Help Overview

The discussion revolves around the calculation of the number of electrons corresponding to a charge of -20 C, specifically in the context of a lightning bolt. Participants are exploring the implications of negative charge and the nature of electrons in electrical charge calculations.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the formula N = Q/e and question the meaning of obtaining a negative number of electrons. There is an exploration of the definitions of charge and the implications of using positive versus negative values in calculations.

Discussion Status

Some participants have provided insights into the nature of electrical charge and the definition of the elementary charge. There is recognition of the confusion surrounding negative charges and the interpretation of the results, but no consensus has been reached on the implications of these definitions.

Contextual Notes

Participants are navigating the definitions and conventions used in electrical charge calculations, particularly regarding the sign of the charge associated with electrons. The discussion reflects an underlying assumption that the charge of an electron is negative, which influences the interpretation of the results.

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3. In a lightning bolt, it is estimated that a charge of -20 C is transferred from a cloud to the Earth. How many electrons make up such a lightning bolt?

N = Q/e

N = -20c / 1.6 x 10^-19

N = -1.25x10^20

I'm pretty sure this is the right answer. What I'm wondering is... how can I have a negative number of electrons? This makes this formula seem flawed to me. I guess I can just remove the negative sign after the fact, is that what most people do?
 
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If you are going to take e to be a positive number, then the charge of the electron has to be -e. You have a positive number of particles. Good that you recognized that your answer didn't make sense.
 
The electrical charge is either positive or negative. The Coulomb was defined as positive (since it is the amount of charge carried by 1A for one second and the current is defined as going from positive voltage to negative). So a quantity of electrons is negative since they have negative change.
 
This is the formula we were given:

Q = Ne

Where Q is the charge in coulombs, N is the number of electrons,
and e is the elementary charge (1.6 x 10^-19 C).

So the elementary charge is actually -1.6 x 10^-19 C whenever you're dealing with electrons?
 

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