1. The problem statement, all variables and given/known data Exercise in integration: Using the Electric Field E of a straight line segment of charge, find the electric field at height 10 cm above the centre of a rectangle of sides 10cm and 20 cm carrying charge density 4 μC/m2. 2. Relevant equations µ=Q/L µ = charge density Q = total charge L = length of line charge μ = charge density = 4 μC/m2 E = 1/4πε0 Q/r2 - Electric Field surrounding point charge. 3. The attempt at a solution Electric Field surrounding a point charge: E = 1/4πε0 Q/r2 Electric field at the location of a test charge q due to a small chunk of charge in the line dQ dE = 1/4πε0 dQ/r2 The amount of charge dQ can be restated in terms of charge density dQ = μ dx dE = 1/4πε0 μ dx/r2 Change dx to dθ and sweep different angles and substitute dθ/a for dx/r2 dE = 1/4πε0 μ dθ/a2 dEy = dE cosθ dEy = 1/4πε0 μ / a cosθ dθ Ey = ∫ 1/4πε0 μ / a cosθ dθ (with θ going from +θ to -θ) Can I just do the same thing in the other direction and add the two? i.e. Ex = ∫ 1/4πε0 μ / a cosθ dθ (with θ going from +θ to -θ) so Ey + Ex = electric field at height above the rectangle? The question said to use the 'Electric Field E of a straight line segment of charge' so I thought it just meant to break it up into two line segments. All I would need to do then is calculate the angles from each side of the rectangle.