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Strength of an Electric Field 
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#1
Apr2907, 03:28 PM

P: 8

Hello. This is my first time here, so let me know if I'm doing anything wrong "postingwise."
1. The problem statement, all variables and given/known data The electric potential in a region of space is V= (260 x^2  180 y^2) V, where x and y are in meters. What is the strength of the electric field at (2.00 m, 3.00 m) ? x = 2.00 m y = 3.00 m 2. Relevant equations E = grad(V) 3. The attempt at a solution E = grad(V) = (520(x)  360(y)) = (40) = 40 I feel really stupid because it's not the right answer... What am I doing wrong? Thanks in advance! 


#2
Apr2907, 03:40 PM

P: 2,046




#3
Apr2907, 03:45 PM

P: 8

I'm still a bit confused.... Well, I have to take into account the direction, too, but.... How do I account for it in the equation?



#4
Apr2907, 04:02 PM

P: 2,046

Strength of an Electric Field
Given some arbitrary scalar field V = V(x,y), how would you write down its gradient (in Cartesian coordinates)?



#5
Apr2907, 04:05 PM

P: 8

V = partial x + partial y?
Well, grad V = partial x + partial y 


#6
Apr2907, 04:11 PM

P: 2,046

[tex]\nabla V = \frac{\partial V}{\partial x}\hat{i} + \frac{\partial V}{\partial y}\hat{j}[/tex] The gradient tells you the direction in which the scalar field, V, is increasing the fastest (at some point). Since a direction is involved it is a vector. But remember, the question asks for the strength of the field, which is the magnitude of the field. 


#7
Apr2907, 04:13 PM

P: 8

ah ****... i'm stupid..... thx :P



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