PROBLEMS
163
S
0.56 k
�
9 V
27 V
2.2 k
�
I
5 V
V
1
+–
1.2 k
�
FIG. 5.79
Problem 9.
120 V
1 k
�
I
V
2
+–
2 k
�
V
3
+–
3 k
�
V
1
+–
R
T
FIG. 5.80
Problem 10.
9.
Determine the current
I
and the voltage
V
1
for the net-
wo
rk of Fig. 5.79.
10.
F
or the circuit of Fig. 5.80:
a.
Find the total resistance, current, and unknown volt-
age drops.
b.
V
erify Kirchhoff’s voltage law around the closed
loop.
c.
Find the power dissipated by each resistor, and note
whether the power delivered is equal to the power dis-
sipated.
d.
If the resistors are available with wattage ratings of
1/2, 1, and 2 W, what minimum wattage rating can be
used for each resistor in this circuit?
11.
Repeat Problem 10 for the circuit of Fig. 5.81.
*12.
Find the unknown quantities in the circuits of Fig. 5.82
using the information provided.
13.
Eight holiday lights are connected in series as shown in
Fig. 5.83.
a.
If the set is connected to a 120-V source, what is the
current through the bulbs if each bulb has an internal
resistance of 28
�
1
8
�
�
?
b.
Determine the power delivered to each bulb.
c.
Calculate the voltage drop across each bulb.
d.
If one bulb burns out (that is, the filament opens),
what is the effect on the remaining bulbs?
To solve these problems, we need to apply the principles of electrical circuits and use various formulas and concepts.
Problem 9:
To determine the current (I) and voltage (V1) for the network in Fig. 5.79, we need more information about the resistances and connections in the circuit. Look for additional details in the problem statement or diagram and use Ohm's Law (V = I * R) and Kirchhoff's Laws to analyze the circuit.
Problem 10:
a. To find the total resistance, current, and unknown voltage drops in the circuit of Fig. 5.80, we need the values of the resistors and any known currents or voltages. Use the series and parallel resistor formulas to calculate the total resistance, apply Ohm's Law to find the current, and analyze the circuit to determine the unknown voltage drops.
b. Verify Kirchhoff's voltage law by summing the voltage drops around the closed loop (circuit) and comparing it to the voltage source's value. Kirchhoff's voltage law states that the algebraic sum of the potential differences in any closed loop of a circuit must equal zero.
c. To find the power dissipated by each resistor, use the formula P = V * I (power = voltage * current) for each resistor in the circuit. Compare the total power delivered (the power source's value) to the sum of power dissipated by all the resistors.
d. Determine the minimum wattage rating for each resistor in the circuit by finding the highest power dissipation among all the resistors. Choose a wattage rating greater than or equal to that value.
Problem 11:
Repeat the steps outlined for Problem 10, but for the circuit shown in Fig. 5.81. Analyze the circuit, calculate the total resistance, current, unknown voltage drops, verify Kirchhoff's voltage law, and find the power dissipated by each resistor.
Problem 12:
To find the unknown quantities in the circuits of Fig. 5.82, use the information provided, such as known values of resistors, currents, or voltages. Apply Ohm's Law and Kirchhoff's Laws to calculate the unknown quantities.
Problem 13:
a. Calculate the current through the bulbs in the circuit of Fig. 5.83 by dividing the source voltage (120V) by the total resistance. Use the given internal resistance of each bulb to determine the effective resistance.
b. Determine the power delivered to each bulb by using the formula P = V^2 / R (power = voltage^2 / resistance) and substituting the values for voltage and resistance.
c. Calculate the voltage drop across each bulb using Ohm's Law (V = I * R) and substituting the respective current and resistance values.
d. If one bulb burns out (opens), the circuit becomes incomplete, and the remaining bulbs will not receive any current or voltage. As a result, the remaining bulbs will also not light up.