- #1
Crusaderking1
- 159
- 0
Homework Statement
A straight, nonconducting plastic wire 8.00 cm long carries a charge density of 125 nC/m distributed uniformly along its length. It is lying on a horizontal tabletop.
A) Find the magnitude and direction of the electric field this wire produces at a point 5.50 cm directly above its midpoint.
B) If the wire is now bent into a circle lying flat on the table, find the magnitude and direction of the electric field it produces at a point 5.50 cm directly above its center.
I have tried to figure it out, but I am having some issues.
Homework Equations
theta = r/(L/s)
E = Q/2πrεoL = ρL/2πrL = ρ/2πεor
The Attempt at a Solution
E = 125*10^-9/((2pi(0.055)8.85*10^-12 = 4.0871*10^4
Ey = Esin(theta)
theta = r/(L/s) = arctan(2*0.055)/0.08 =arctan(1.375) = 53.97 degrees
Ey= 4.0871*10^4 * sin53.97 degrees = 3.31*10^4
Alternatively, would I do arctan again for 53.57 degrees for 88.938 degrees? Then multiply it by 4.0871*10^4? The answer would be 4.086*10^4
Is this right?? Please help me.
b)
r= L/2pi = 0.08/2pi = 0.0126 m
d = square root(0.0126^2+0.055^2) = 0.0564 m
Ey = Esin(theta)
theta = arctan(0.055)/(0.0126m) = 77.1 degrees
Ey = PL/4piEor^2 = 125*10^-9 * 0.08 / 4pi(8.85*10^-12(0.055^2) = 2.97*10^4
Last edited: