a circular plastic disk with radius R = 2.00 cm has auniformly distributed charge Q = + (2.00 x 106) e on oneface a circular ring of width 30 m is centred on that facewith the centre of that width at radius r = 0.50 cm in coulombswhat charge is contained with in the width of the ring In step 3, where is this coming from and the steps afterthat A'= (R~r)(R+r) = dr(R-r+2r) Please show me all the steps becasue I m confuse on how thearea is being calculating. Thanks a circular plastic disk with radius R = 2.00 cm has auniformly distributed charge Q = + (2.00 x 106) e on oneface a circular ring of width 30 m is centred on that facewith the centre of that width at radius r = 0.50 cm in coulombswhat charge is contained with in the width of the ring In step 3, where is this coming from and the steps afterthat A'= (R~r)(R+r) = dr(R-r+2r) Please show me all the steps becasue I m confuse on how thearea is being calculating. Thanks
Explanation / Answer
from dA = 2 r dr dq = dA so that we have dq = (Q / R2) 2 rdr where we have used the fact that the disk isunifirmly charged to set the surface charge density equal to thetotal charge (Q) divided by the total area next we set r = 0.0050 m and make theapproximation dr = 30 x 10-6 m so we get that dq = 2.4 x 10-16 C