Concept explainers
INTERPRET Ibis problem deals with the electric field of a charged disk. We want to show that the expre derived in Example 218 has the correct asymptotic behavior.
Develop From Example 22.8, the electric field on the axis (x > 0) of a charged disk of radius a is
In the limit where x >> a, the quantity
EVALUATE Inserting the above approximation into the exact expression, we obtain
which is like that or a point charge.
ASSESS As always, a finite-size charge distribution looks like a point charge at a large distance.
68. Show that the result of Example 22.8 approaches the field of a point charge for x >> a. (Hint: You’ll need to apply the binomial approximation from Appendix A to the expression
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