Page 733 - SUBSEC October 2017_Neat

02238020/CAPE SPEC/MS/2017
3

Question 1 continued KC UK XS
sectional area A. The volume of the segment is L x A.
1
The charge carriers travel at speed v
(h) Then speed = dist/time  V = L/t

(i) Number of charge carriers per unit volume = n

The total charge in the segment is enVtA (1)
(ii) 1 1

The current flowing in charge passed/time
(iii) 1 1
i.e. I = enVtA/t = enVA (1)

hence V = I/neA (1) 1

(i)

2
I = P/V (1) = 500/100 = 5 A (1)

R = V (1) = 100 = 20 (1)
I 5

R = L (1)
A

L = RA
2


-6
= 20 x 2.6 x 10 (1) = 104 m (1)
-7
5.0 x 10 13 15 2

V = I_
neA
-6
-4
3
Volume of conductor = 104 x 2.6 x 10 = 2.704 x 10 m

n = 2.704 x 10 x 9.0 x 10
-4
28
= 2.43 x 10
25

V = 5 (1)
-6
25
2.43 x 10 x 1.6 x 10 -19 x 2.6 x 10

-1
= 0.49 ms (1)

Total 30 marks