P27_053.PDF

(58 KB) Pobierz

Chapter 27 - 27.53

53.(a)

V = iR = iρ L

A =

(12 A)(1 . 69

×

10 − 8 Ω

·

m)(4 . 0

×

10 − 2 m)

=3 . 8

×

10 − 4 V .

π (5 . 2

×

10 − 3 m / 2) 2

(b) Since it moves in the direction ofthe electron drift which is against the direction ofthe current, its

tail is negative compared to its head.

(c) The time oftravel relates to the drift speed:

t =

L

v d

=

lAne

i

= πLd 2 ne

4 i

=

π (1 . 0

×

10 − 2 m)(5 . 2

×

10 − 3 m) 2 (8 . 47

×

10 28 / m 3 )(1 . 60

×

10 − 19 C)

4(12 A)

= 238 s = 3 min 58 s .