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neha123
is electric field of sphere and disk same?
What do you mean? They could both have the same strength, but not the same vectors.
find electric field caused by a sphere of radius R with uniform surface charge density sigma at a point along axis of disk at a distance x from its centre should i follw same method as for a disk?.
electric field at a distance R by sphere of uniform charge density is if R> radius of sphere \[E=\frac{ Q }{ 4 \pi \epsilon R^2 }\] and for R < radius of sphere (A) is \[E=\frac{ Q R }{ 4 \pi \epsilon A^3 }\] now if we talk about disc then, lets say at a distance X from the center of disc along the axis of rotation \[E=2 \pi \sigma k(1- \frac{ X }{ \sqrt{X^2+R^2} } )\] for X>0, R is radius of disc and for X<R electric field is \[E \approx 2 \pi \sigma k\]
now, i hope you can better judge and analyse if its same and at what distance or not :)