64 DC circuit analysis
Figure 3.45
1
4V 2V 2V(~+) I
I1
O~ ]20~ ~30~40~
7 Three 20 1~ resistors are connected in star and a voltage of 480 V is applied
across two of them. If three other resistors (identical to each other) are
connected in delta and the same supply is connected across one of them,
determine (a) the value of the delta connected resistors and (b) the current
in each of the delta connected resistors. The supply current is the same as
before.
8 Three resistors having resistances of 100 1~, 200 1~ and 1 ~ are connected
in delta. Determine the resistances of the equivalent star connected
resistors.
9 In the circuit of Fig. 3.42, a load resistor (RE) is connected between
terminals A and B. Determine (a) the value of RE in order that the power
transferred to it from the source shall be a maximum and (b) the
maximum power transferred.
10 A network has a Thevenin equivalent circuit consisting of a source Eoc in
series with a resistance Roc so far as its output terminals A and B are
concerned. When a load resistor of resistance 25 ~ is connected across the
output terminals, the load current is 48.3 mA and when the load resistance
is doubled the load current falls to 25.9 mA.
(a) Determine the values of Eoc and Roo (b) Calculate the output
voltage when a load of 40 1~ resistance is connected between A and B.
11 A circuit has three nodes A, B and C. Between A and C is connected a
voltage source of 20 V (having an internal resistance of 5 1~) in parallel
with a resistor of 15 1~ resistance. Between B and C is connected a voltage
source of 10 V (having an internal resistance of 2 ~) in parallel with a
resistor of 8 ~ resistance. The negative terminals of both sources are
connected to the node C. Between A and B is connected a resistor, R of
10 ~ resistance. Determine (a) the current through the resistor R, (b) the
necessary resistance required in series or in parallel with R for the power
to be transferred to terminals AB to be a maximum and (c) the value of
the maximum power transferred.
12 A bridge circuit has nodes A, B, C and D. The circuit is arranged as
follows:
between A and B: a resistance of 10 1~