Nova Chapter 14 # 9 Electric Field

[MrNeuro]

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What is the magnitude of the electric field at point E?

I know that the fields due to B and C cancel each other out but how does the field due to A cancel out?

 

[milski]

B and C don't cancel each other completely. Their horizontal components cancel but they have a vertical component pointed in the same direction. A, B and C together do cancel each other.

Horizontal components:
Ah = 0
Bh = -cos 30
Ch = cos 30
Ah+Bh+Ch=0

Vertical components:
Av = 1
Bv = -sin 30
Cv = -sin 30
Av+Bv+Cv = 1 - 2sin30 = 1 - 2*1/2 = 0

 

[MrNeuro]

got it thanks