Basic Concepts

AEE1000 / MEC1151 - Electrical Circuits and Analysis
Dr Hong Fan, University of Glasgow, 2022

Tutorial – Topic 1 : Basic Concepts


[Charge and Current]
1.1 Determine the current flowing through an element if the charge flow is given by
(a) q (t ) = (3t + 8) mC
"ᵗ '

C) alt) 20 e cos 50T =



(b) q (t ) = (3e − t − 5e −2t ) nC :-/ It) :
dadt
(c) q (t ) = 20e −4t cos(50t ) µ C - ↳ᵗ
cos 50T
"+
Sin -50T
=
-80C -
1000 @
1. 12 ) qlt) =
(31-+8) t "
b) g. It ) ( ze b- e-
-
= -
j
"ᵗ
i. I / E) = d9_ i. 1 It) = DI
: -
e- ( 8005501-+1000 sin 50T)µA
dit #
dit
=
3mA # ᵗ "
1nA
-


=L-3@
-



+ toe
*
1.2 A current of 3.2 A flows through a conductor. Calculate how much charge passes through any
cross-section of the conductor in 20 s.
/ A :/ Cls

i.
Charge = 3.2×20


: 64C
#




1.3 The charge entering a certain element is shown in Figure 1.1. Find the current at:
(a) t = 1 ms (b) t = 6 ms (c) t = 10 ms b) @ t 6ms =


1- 32 ) @ t -2ms
-


91-11=80MC
91T) -80mL
-




:/ = = da
:@ t =
1mg at

91T) =
40mC = 80--80
6- 2
dqlt)
:-/ =

;÷n =

at =
0A
#
80 -
40
=

I
c) @ t -8ms -




= 40A
# qlt) = SOMC

Figure 1.1 i. @ t = 10ms

9. (t) = 40mC

.
'

.
/ =
rise
-
= dqct)
run It
-
40 -
80
- -


to -
8

= -
20 A
#