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

[elowe93]

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?

 

[jk86]

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.

 

[rude man]

You should not have multiplied.

 

[BiGyElLoWhAt]

use unit analysis. What are the units of an e field? what are the units of voltage?

 

[elowe93]

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?