Ques1) In the figure shown above, a thin glass rod forms a semicircle of radius r = 5m. Charge is ubiformly distributed along the rod with +q in the upper half and -q in the lower half. What are the amg and direction of the electric field E at P, the centre of the semicircle?
Ques2) 
In the figure, two curved plastic rods, one of charge +q and other charge -q, forms a circle of radius R in an x-y plane. What are the magnitude and direction of the electric field produced at P, the centre of the circle.
Ques3) Calculate the number of coulombs of posoitve charge in 250 cm3 of neutral water.
1
dq=pds [P=LINEAR CHARGE DENSITY]
dE=p *ds*sin θ/4ΠεR^2
dE=p*dθ*sinθ/4ΠεR
∫dE =(p/4ΠεR )*∫sinθ dθ [lower limit=0°
upper limit=180°]
E=2p/4ΠεR THIS IS FOR THE
UPPER SEMICIRCULAR PORTION IN THE DOWNWARD DIRECTION.
SIMILARLY FOR THE LOWER PORTION E=2p/4ΠεR IN THE DOWNWARD DIRECTION
HENCE NET ELECTRIC FIELD E=4p/4ΠεR
