Resolução - Halliday - Volume 3 - Eletricidade E Magnetismo - P22 047

Transcript

47. The charge dq within a thin section of the rod (of thickness dx) is ρ A dx where A = 4.00 × 10−4 m2 and ρ is the charge per unit volume. The number of (excess) electrons in the rod (of length L = 2.00 m) is N = q/(−e) where e is given in Eq. 22-14. (a) In the case where ρ = −4.00 × 10−6 C/m3 , we have q ρA N= = −e −e
L dx = 0 |ρ| A L e which yields N = 2.00 × 1010 . (b) With ρ = bx2 (b = −2.00 × 10−6 C/m5 ) we obtain N= bA −e
L x2 dx = 0 |b| A L3 = 1.33 × 1010 . 3e