# Stopping Potential

1. Sep 15, 2013

### kougou

[URGENT! Stopping Potential~~~~~~~###~~~~~~~~~~~~~~~~

1. The problem statement, all variables and given/known data

max Kinetic_energy= e*Vs=hf-work_function

Vs is the stopping potential

The attempt at a solution

I am wondering, does this stopping potential refers the voltage difference of
V_Emitter (where the line shines on) - V_collector(where the electron travels to), and thus, the stopping potential is usually positive?

Also, for that equation max kinetic_energy= e*Vs, 'e' is just the charge= +ve 1.602*10^-19?
so that the max kinetic energy in this case, (+5 V)*(+ 1.602*10^-19)= +ve number?

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Last edited: Sep 15, 2013
2. Sep 16, 2013

### Staff: Mentor

If you use e as elementary charge, it has to be positive.
If you use the electron charge, you need the opposite direction, and a negative voltage. That is just a matter of definition.
What do you mean with "+ve number"? If you add units, you will get the right result.