Chapter 2 Solutions Section 2.1 Introduction 2.1 Current source 2.2 Voltage source 2.3 Resistor 2.4 Capacitor 2.5 Inductor Section 2.2 Charge and Current 2.6 b) The current direction is designated as the direction of the movement of positive charges. 2.7 The relationship of charge and current is t q(t ) = ! i(t ) + q(t 0 ) dt t0 so t q(t ) = ! 2 sin ( " t ) + q(t0 ) 10 dt t0 & '2 # q(t )= $ cos( ( t )! + q(t0 ) 10 " t0 %10(
2.8 The coulomb of one electron is denoted by e and t t
q(t ) = ! i (t ) + q(t0 ) dt t0 So
1 n(t ) = q (t ) / e = ! 12t dt + q(t 0 ) e t0
If t0 = 0 and q(t 0 ) = 0 ,
6 n(t ) = t 2 e
t
2.9
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q(t ) = ! idt t q(t )= ! 5dt
0
q(t ) = 5t
2.10
q(t )= 0 [ t ]= 5(5)! 5(0 ) = 25 Coulombs 5
5
2.11 Using the definition of current-charge relationship, the equation can be rewritten as: i= dq !n = e dt !t
Thus, the current flow within t1 and t2 time interval is,
(5.75 ! 2) " 1019 i= (!1.6 " 10 !19 ) = !3 A 2
The