Help finding the electric feild strength in a uniform E-field

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SUMMARY

The electric field strength across a membrane with a voltage of 78.7 mV and a thickness of 8.52 nm is calculated using the formula E = V/d. The correct calculation yields an electric field strength of approximately 9,237,089 V/m. The confusion arose from an initial miscalculation of voltage and misunderstanding of the sign convention in electric field equations. The electric field is typically expressed as a positive value, representing the direction of force on a positive charge.

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elowe93
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Homework Statement



The voltage across a membrane forming a cell wall is 78.7 mV and the membrane is 8.52 nm thick. What is the electric field strength? (The value is surprisingly large, but correct.) You may assume a uniform E-field.

Homework Equations



E=-Vd

The Attempt at a Solution



E=-(.00787V(8.52e-9m)) = 7.9e-11 V

i don't understand why this is wrong?
 
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elowe93 said:

The Attempt at a Solution



E=-(.00787V(8.52e-9m)) = 7.9e-11 V

i don't understand why this is wrong?

The problem stated that the voltage was 78.7 mV, but you have written that down as 0.00787=7.87mV. Also check your multiplication.
 
You should not have multiplied.
 
use unit analysis. What are the units of an e field? what are the units of voltage?
 
Okay, so i did E=(.0787)/(8.52e-9) to get 9237089 V/m is this correct? or should it be negative because in some of the equations I am finding for this it has a negative. I feel like it should be positive though is this right?
 

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