Dc Circuit theory exam question - reseeds

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7 Οκτ 2013 (πριν από 4 χρόνια και 2 μήνες)

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DC circuit theory exam question


In the ci
rcuit
shown below
the value of the load resistance, R, is chosen so that the
load power
dissipation
is maximised.


a) Derive the Thevenin equivalent of the network to which the
load
resistance R is

connected.


b
) Calculate the value of R to maximise the load power
dissipation and the value of the


maximum load power.


c) With the value of R calculated in part b) connected in the circuit, calculate the power
supplied by each of the sources.





12V



1
A

1



4



R

12

Solution

a) The circuit can be reduced to its Thevenin equivalent using source equivalence and combining
resistances in series and parallel:



b) Required load resistance = 4





Load powe
r =
E
2
/4R =
(6
*
6
)/(4*4) =

2.25

W

c) With the load resistance connected, load voltage =
3
V and load current =
3 / 4 = 0.75
A,

so
the electrical conditions in the
remainder of the
circuit are:



So:

Power from 1A source =
3.75

*

1.0 =
3.75
W


Power from
1
2
V

source =
12 * 0.69

=
8
.25

W


12V



1A

1



4



R

12

1





1A

4

R

1A

12



2A



R

6
V



4

R

3

1



0.94A

1



1
A



4



4

0.75A

0.75
V

3V

12V



12

3.75V

1.69A

0.69A