
Concept explainers
Calculate the power dissipated in each resistor in the circuit of Figure 3.104.

Answer to Problem 60P
The power dissipated in 1 Ω, 2 Ω, 4 Ω, and 8 Ω resistors are 1600 W, 3872 W, 14400 W, and 4608 W respectively.
Explanation of Solution
Given data:
Refer to Figure 3.104 in the textbook for the nodal analysis. In the given circuit, io is the current flow through 1 Ω resistor.
Calculation:
Modify the given figure with the representation of node voltage as shown in Figure 1.
Apply Kirchhoff’s current law at node v1 in Figure 1.
v1−01+v1−2804+0.5io=0 (1)
With reference to Figure 1, write the expression for io through 1 Ω branch.
io=v1−01 (2)
Substitute equation (2) in (1).
v1−01+v1−2804+0.5(v1−01)=0v1+v14−2804+0.5v1=0v1+0.25v1+0.5v1=2804v1+0.25v1+0.5v1=70
Simplify the equation as follows.
v1+0.25v1+0.5v1=701.75v1=70v1=701.75v1=40 V
Apply Kirchhoff’s current law at node v2 in Figure 1.
v2−2808+v2−02−0.5io=0 (3)
Substitute equation (2) in (3).
v2−2808+v2−02−0.5(v1−01)=0v28−2808+v22−0.5v1=0−0.5v1+(18+12)v2=2808
−0.5v1+0.625v2=35 (4)
Substitute 40 V for v1 in equation (4).
−0.5(40)+0.625v2=35−20+0.625v2=350.625v2=35+200.625v2=55
Simplify the equation as follows.
v2=550.625=88 V
Write the expression for power dissipated through 1 Ω resistor.
P1 Ω=(v1−0)21 Ω (5)
Substitute 40 V for v1 in equation (5) to find P1 Ω.
P1 Ω=(40 V−0)21 Ω=1600 W
Write the expression for power dissipated through 2 Ω resistor.
P2 Ω=(v2−0)22 Ω (6)
Substitute 88 V for v2 in equation (6) to find P2 Ω.
P2 Ω=(88 V−0)22 Ω=7744 V22 Ω=3872 W
Write the expression for power dissipated through 4 Ω resistor.
P4 Ω=(v1−280)24 Ω (7)
Substitute 40 V for v1 in equation (7) to find P4 Ω.
P4 Ω=(40 V−280 V)24 Ω=(−240 V)24 Ω=57600 V24 Ω=14400 W
Write the expression for power dissipated through 8 Ω resistor.
P8 Ω=(v2−280 V)28 Ω (8)
Substitute 88 V for v2 in equation (8) to find P8 Ω.
P8 Ω=(88 V−280 V)28 Ω=(−192 V)28 Ω=36864 V28 Ω=4608 W
Conclusion:
Therefore, the power dissipated in 1 Ω, 2 Ω, 4 Ω, and 8 Ω resistors are 1600 W, 3872 W, 14400 W, and 4608 W respectively.
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Chapter 3 Solutions
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