AB and CD are two perpendicular diameters of a circle of circumference `20pi` cm. There are +10 esu, +10 esu, +10 esu and -10 esu of charges at A, B, C and D respectively. What is the Intensity of electric field at the centre O of the circle? What is the direction of the field?

Explanation

Suppose, O is the centre of the circle [Fig. 2.26].

Radius of the circle = r.
Here, `2pir=20pi` or, r=10 cm
Intensities of electric field at O due to the charges at A and B cancel each other, because the two fields are equal and opposite.Intensity at O due to the charge at C
`=10/((10)^(2))=1/10`dyn.stat`C^(-1),` along `vec(OD)`
Intensity at O due to the charge at D
`=10/((10^(2))=1/10` dyn.stat`C^(-1),`along `vec(OD)`
`therefore` Resultant intensity at O
`=(1/10+1/10)=0.2` dyn.stat`C^(-1),` along `vec(OD)`