Download Series Circuit - Spring Branch ISD

A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
Conceptual Physics Circuits Outline
Hewitt: Chapter 34 & 35
Exercises: 16 Electrostatics
Fill in the Charts completely
Variables introduced or used in chapter:
Quantity
Symbol
charge
time
current
Resistance
Potential Difference / Voltage
Capacitance
Work
Power
Units
Formula Chart*
*In Class, we will use x for horizontal motion, and y for vertical motion instead of ‘d’
Current
Potential Difference (Ohm’s Law)
Capacitance
Electric Power
P = IV
Total Resistance in Series
Total Resistance n Parallel
Define the following terms using COMPLETE SENTENCES:
Current
Electric Resistance
Potential Difference
Voltage Source
Ohm’s Law
Direct Current
Circuits p 1
A1 Conceptual Physics
Spring 2013
Alternating Current
Circuits
Chapters 34 & 35
Electric Power
Battery
Circuit
Open Circuit
Closed Circuit
In Series
In Parallel
Series Circuit
Parallel Circuit
Schematic Diagrams
Equivalent Resistance
Overload
Formula Summary:
𝑂ℎ𝑚𝑠 𝐿𝑎𝑤: 𝑉 = 𝐼𝑅
𝑃 = 𝐼𝑉
𝑆𝑒𝑟𝑖𝑒𝑠: 𝑅𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 = 𝑅1 + 𝑅2 + 𝑅3 + ….
𝑃 = 𝐼2 𝑅
𝑃𝑎𝑟𝑎𝑙𝑙𝑒𝑙:
𝑃=
1
𝑅𝑒𝑞
=
1
𝑅1
+
𝑉2
𝑅
Circuits p 2
1
𝑅2
A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
Circuits Homework Problems
Ohms Law, Power
1. Calculate the current where 15 coulombs of charge pass a point in 3 seconds.
[5A]
2. Calculate the current of a lightning bolt that delivers a charge of 35 coulombs to
the ground in a time of 1/1000 second. [35,000 A]
3. Calculate the current in a 140 watt electric blanket connected to a 120 volt
outlet. [1.17 A]
4. The current through a light bulb connected across the terminals of a 120 volt
outlet is 0.5 A. At what rate does the bulb convert electric energy to light? (hint:
remember power measures the rate at which energy is transferred) [60 W]
5. What current flows through a 75 watt light bulb connected to a 120 V outlet.
[0.625 A]
6. An automobile headlight with a resistance of 30Ω is placed across a 12 V
battery. What is the current through the circuit? [0.4 A]
7. A transistor radio uses 2 x 10-4 A of current when it is operated by a 3 V battery.
What is the resistance of the radio circuit? [15,000 Ω]
8. A motor with an operating resistance of 32Ω is connected to a voltage source.
The current in the circuit is 3.8 A. What is the voltage of the source? [121.6 V]
9. A lamp draws a current of 0.5A when it is connected to a 120 V source.
a. What is the resistance of the lamp? [240 Ω]
b. What is the power consumption of the lamp? [60 W]
10. A 75 W lamp is connected to 120 V.
a. How much current flows through the lamp? [.625 A]
b. What is the resistance of the lamp? [192 Ω]
11. The current through a toaster connected to a 120 V source is 8.0 A. What is the
power rating (ex: 65 Watts) of the toaster? [960 W]
12. A 12V automobile battery is connected to an electric starter motor. The current
through the motor is 210 A.
a. How many joules of energy does the battery deliver to the motor each
second? (hint: look at definition of power) [2520 J/s]
b. What power does the motor use in watts? [2520 W]
13. A flashlight bulb is connected across a 3.0V difference in potential. The current
through the lamp is 1.5 A. What is the power rating of the lamp(Watts)? [4.5 W]
Series Circuits: RE = R1 + R2
14. If three identical lamps are connected in series to a 6 volt battery, what is the
voltage drop across each lamp? [2V]
15. If one of the above three lamps blows out when connected in a series circuit,
what happens to the current in the other two?
16. Calculate the current in a 48 V battery that powers a pair of 30 Ω resistors
connected in series. [0.8 A]
17. Why are household appliances almost never connected in series?
18. As more and more lamps are connected in series to a battery, what happens to
the brightness of each lamp?
19. Consider a 9 V battery in a series circuit with three resistors.
a. If the resistance of one of the resistors increases, how will the
equivalent resistance of the circuit change?
b. What will happen to the current?
c. Will there be any change in the battery voltage?
Circuits p 3
A1 Conceptual Physics
Circuits
Spring 2013
Chapters 34 & 35
20. A string of holiday lights has ten bulbs with equal resistances connected in
series. When the string of lights is connected to a 120 V outlet, the current
through the bulbs is 0.06 A.
a. What is the equivalent resistance of the circuit? [2000 Ω]
b. What is the resistance of each bulb? [200 Ω]
21. A 20.0 Ω resistor and a 30.0 Ω resistor are connected in series and placed across
a 120 V potential difference.
a. What is the equivalent resistance of the circuit? [50 Ω]
b. What is the current in the circuit? [2.4 A]
c. What is the voltage drop across each resistor? [48 V, 72 V]
d. What is the voltage drop across the two resistors together? [120 V]
22. Three resistors of 3.0 k Ω resistor (3.0 x 103 Ω ), 5.0 k Ω resistor, and 4.0 k Ω
resistor are connected in series across a 12 V battery.
a. What is the equivalent resistance? [12,000 Ω]
b. What is the current through the resistors? [0.001 A]
c. What is the voltage drop across each resistor? [3 V, 5V, 4V]
d. Find the total voltage drop across the three resistors. [12 V]
23. A student has a circuit with a 45 V battery, a 475 k Ω resistor (475 x 103 Ω ), and
a 235 K Ω resistor. What is the voltage across the 235KΩ resistor? [14.89 V]
24. A 20.0 Ω lamp and a 5.0 Ω lamp are connected in series and placed across a
difference in potential of 50 V.
a. What is the equivalent resistance of the circuit? [25 Ω]
b. What is the current in the circuit? [2A]
c. What is the voltage drop across each lamp? [40 V, 10V]
d. What is the power used in each lamp? [80 W, 20W]
25. Three identical lamps are connected in series to a 6.0 V battery. What is the
voltage drop across each lamp? [2V]
26. The load across a 12 V battery consists of a series combination of three
resistors of 15 Ω , 21 Ω , and 24 Ω .
a. What is the total resistance of the load? [60 Ω]
b. What is the current in the circuit? [0.2A]
c. What is the voltage drop across each resistor? [3V, 4.2V, 4.8V]
27. A lamp having a resistance of 10 Ω is connected across a 15 V battery.
a. What is the current through the lamp? [1.5 A]
b. What resistance must be connected in series with the lamp to reduce
the current to 0.5 A? [20Ω]
Parallel
28. Two resistors are wired in series. In another circuit, the same two resistors are
wired in parallel. In which circuit is the equivalent resistance greater?
29. You have three resistors: A 5Ω, 10Ω, and a 15Ω.
a. When they are connected in series.
i. Which resistor has the most current in it? (same)
ii. Which resistor has the largest potential difference across
it?[15Ω]
b. When they are connected in parallel.
i. Which resistor has the most current in it? [5Ω]
ii. Which resistor has the largest potential difference across it?
30. Three 15Ω resistors are connected in parallel and placed across a 30V potential
difference.
a. What is the equivalent resistance of the parallel circuit? [ 5Ω]
b. What is the current through the entire circuit? [6A]
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A1 Conceptual Physics
Circuits
Spring 2013
Chapters 34 & 35
c. What is the current through each branch of the circuit? [2A, 2A, 2A]
31. A 12Ω and a 15Ω resistor are connected in parallel and placed across the
terminals of a 15V battery.
a. What is the equivalent resistance of the parallel circuit? [6.7 Ω]
b. What is the current through the entire circuit? [2.25 A]
c. What is the current through each branch of the circuit? [1.25 A, 1A]
Combined Circuits – BE ABLE TO DRAW!
32. Draw circuit diagrams for the following circuits.
a. Three 20Ω resistors connected in series across a 120V generator.
b. A 12Ω and a 15Ω resistor are connected in parallel and placed across
the terminals of a 15V battery.
c. Two 60Ω resistors are connected in parallel. This parallel arrangement
is connected in series with a 30Ω resistor. The entire circuit is then
placed across a 120V potential difference.
d. A 4Ω and an 8Ω resistor are connected in series. This series
arrangement is connected in parallel with a 17Ω resistor. The entire
circuit is placed across a 90V potential difference.
e. Two 5Ω resistors are connected in series. This series arrangement is
connected to two 5Ω resistors connected in parallel. The parallel
arrangement is then connected in series to two more 5Ω resistors, and
the entire circuit is placed across a 120V potential difference.
f. A 2Ω and a 6Ω resistor are connected in series, and their combination is
in parallel with a 12Ω resistor to form a load across a 6V battery.
33. A 30Ω and a 20Ω resistor are connected in parallel. This parallel arrangement
is connected in series with an 8Ω resistor, and the entire circuit is placed across
a 60V potential difference.
Combined Circuits – Problems Extra Credit on Test: SOLVE one!
34. Resistors R1, R2, and R3 have resistances of 37 Ω, 22 Ω and 41 Ω respectively. R1 and
R2 are connected in series, and their combination is in parallel with R3. This
arrangement is then placed across a 60V battery. Draw the circuit diagram.
a. What is the equivalent resistance of the three resistors? [24.19 Ω]
b. What is the size of the circuit breaker required to run this circuit safely?
[2.48A]
c. What is the voltage drop across the 22Ω resistor? [22.44 V]
d. If you added a 4th resistor in parallel with R3, would you trip the circuit
breaker?
35.
Three resistors are connected in parallel (2Ω, 3Ω, 4Ω), and are
connected in series to a 1Ω resistor. The entire circuit is connected to a 9V
generator.
a. What is the total resistance of the circuit? [1.92 A]
b. What is the total current running through the circuit? [4.68 A]
c. What is the current in the 1Ω resistor? [4.68 A]
d. What is the voltage drop across the 3Ω resistor? [4.32 V]
e. What is the minimum sized circuit breaker needed to run this circuit
safely? [5A]
f. If you added another resistor in series with the 1Ω resistor, would the
circuit breaker trip?
Circuits p 5
A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
Series and Parallel Discovery Lab #1
PROBLEM:
How is a series circuit different from a parallel circuit?
MATERIALS:
three light bulbs, wire, switch, battery (or source of electricity)
PROCEDURE:
1. Set up a simple series circuit with one light bulb, wires, switch, and battery.
See diagram below:
2. Note the brightness of the light bulb for future comparison.
3. Set up a series circuit with two light bulbs, switch, wires and battery. See
diagram below:
4. Answer the following questions on your OWN Paper: (5 Each)
A. How does the brightness of this series circuit compare with the first
series circuit? Give possible reasons why this happened.
B. Unscrew one of the light bulbs. What happens to the light bulbs? Why?
5. Set up a series circuit with three light bulbs, switch, wires and battery. See the
diagram below:
6. Answer the following questions: (5 Each)
A. Explain what happened to the brightness when the third light bulb was
added.
B. Unscrew one of the light bulbs. What happened to the other light bulbs?
Why?
C. Define resistance. Compare the resistance to the flow of electricity of
each series circuit.
7. Set up a parallel circuit with two light bulbs, switch, wires and battery. See
diagram below:
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A1 Conceptual Physics
Circuits
Spring 2013
Chapters 34 & 35
8. Answer the following questions based on this circuit: (5 Each)
A. How is the brightness different from the series circuit with two light
bulbs? Why?
B. Unscrew one light bulb. What happens to the other light bulbs? Why?
C. Compare the resistance of this parallel circuit with the series circuit
with two light bulbs.
9. Set up a parallel circuit with three light bulbs, switch, wire and battery. See
diagram below:
10. Answer the following questions based on this circuit: (5 Each)
A. How is the brightness different from the series circuit with three light
bulbs? Why?
B. How is the brightness of this parallel circuit different from the last
parallel circuit with two light bulbs? Why?
C. Unscrew one light bulb and explain what happens to the other light
bulbs. Why does this happen?
D. How is the resistance of this circuit different from the parallel circuit
with two light bulbs? Why?
ANALYSIS: Answer these questions: (5 Each)
1. Identify whether the following circuits are in series or in parallel or both and
explain how you know:
A.
B.
C.
2. Give an example of a series circuit and a parallel circuit in your home.
3. What is the basic difference between series and parallel circuits?
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A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
4. If five light bulbs were connected in the same circuit, in which circuit (series or
parallel) would they have the least total resistance to the flow of electrons?
5. Why do some companies make strings of holiday lights in parallel circuits
rather than in series circuits?
6. What was the purpose of the switch in each of the circuits?
7. Voltage is often defined as the push behind the electrons. In which circuit do
you think that the electrons divide up their voltage to complete their path?
Explain how you decided.
8. Make a chart comparing the characteristics of series and parallel circuits.
Characteristics could include brightness of bulbs, number of paths, resistance,
voltage, unscrewing one light bulb etc.
Circuits p 8
A1 Conceptual Physics
Spring 2013
Electric Circuits with CPO Equipment Lab #2
Circuits
Chapters 34 & 35
INTRODUCTION: A simple electric circuit contains one electrical device, a battery and
a switch. Flashlights use this type of circuit. However, most electrical systems, such as
a stereo, contain many electrical devices connected together in multiple circuits. This
investigation introduces two ways to connect multiple devices in a circuit. Use the CPO
equipment to investigate this phenomenon.
Part 1 – Series Circuits
1. Using two batteries, build the simple circuit with three light bulbs and a switch
across as shown above.
2. Set the meter to DC volts. Close the switch and measure the voltage across the
different places by touching the meter’s leads to the bulbs’ terminals. Record
the voltage in Table 1
Table 1: Voltage Measurements (Volts)
Between A and B
Between B and C
Between C and D
Between A and D
Part 2 – Thinking About What You Measured
a. What relationships do you see among the voltage measurements in Table 1?
b. What do the voltage measurements tell you about the flow of energy in the
circuit?
Part 3 – The Current in Series Circuits
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A1 Conceptual Physics
Circuits
Spring 2013
Chapters 34 & 35
1. Set the meter to DC amps. Measure the current by opening the switch and touching
the leads of the meter to the terminals of the switch in the three bulb circuit.
Record measurements in Table 2.
2. Remove one bulb and replace it with a wire. Measure and record the current for
the two-bulb circuit.
3. Remove a second bulb and replace it with a wire. Measure and record the current
again for the one-bulb circuit.
Table 2: Current Measurements (amps)
Three Bulbs
Two Bulbs
One Bulb
Part 4 – Thinking About What You Observed
a. What happened to the current in the circuit as the number of bulbs is reduced?
Explain why this occur using Ohm’s law and the concept of resistance.
b. What happens to the other two bulbs when one bulb is removed from the threebulb circuit? Try it and explain why the circuit behaves as it does.
Part 5 – Short Circuits
A short circuit is an easy (but dangerous) shortcut that current can travel through to
avoid one or more of the electrical components in the circuit.
1. Rebuild your three-bulb circuit with the switch open.
2. Check the current and observe which bulbs light and how bright they are.
3. Add a section of wire that bridges the last two bulbs in the circuit. This wire is
the “short circuit.”
4. Complete the circuit (with the switch open) using the meter to measure the
current. Observe which bulbs light and how bright they are.
Part 6: Thinking About What You Observed
Three Bulbs in Series
Three Bulbs with Two short circuited
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Spring 2013
Circuits
Chapters 34 & 35
a. Compare the current in the three-bulb circuit with the current when two bulbs
are bypassed by a short circuit. Which is greater? Use Ohm’s law and the
concept of resistance to explain why.
b. How does the current in the “short circuit” version compare with the current
you measured in a one bulb circuit? Explain why this should be true.
c. How does the resistance of a wire compare to the resistance of a bulb? Measure
the resistances to test your answer. NOTE: Most meters cannot measure very
low resistance and display “0,00” when the resistance is lower than 0.01Ω.
d. Why would a short circuit be dangerous? Discuss (as a group) the
consequences of very large currents in wires of different sizes.
Part 7: Parallel Circuits
1. Build a circuit with two batteries, a switch and three bulbs as shown in the
diagram.
2. Close the switch and measure the voltage across the battery. All three bulbs
should be lit.
3. Measure the voltage across each bulb by touching the leads of the meter to the
terminals of each bulb separately.
4. Set the meter to DC amps. Measure the total current in the circuit by opening the
switch and touching the leads of the meter to the terminals of the switch.
Table 4: Voltage and Current in a Parallel Circuit
Total Circuit
Bulb 1
Voltage (V)
Bulb 2
Bulb 3
Current (A)
Part 8: Thinking About What You Observed
a. Compare the brightness of the bulbs in the parallel circuit with the brightness
in the series circuit.
b. Compare the total current in the single-bulb circuit, the three-bulb series
circuit, and the three-bulb parallel circuit. Propose a relationship between the
currents that agrees with the brightness of the bulb.
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A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
c. Remove one bulb from the parallel circuit by unscrewing it from its socket.
Observe what happens to the remaining bulbs. Did the other two bulbs
continue to light when the third bulb was removed from the parallel circuit?
Explain why. How does this differ from what happened with the series circuit?
d. Do you think the electrical outlets in your home are connected in series or
parallel circuit? Give two reasons why one type of circuit has an advantage
over the other for connecting outlets.
CONCLUSION: (20 pts)
completing this lab?
What 3 ideas or concepts do you understand better after
Rubric:
Title: 4 pts
Table Records: 2 pts X 14 = 28 pts
Questions: 4pts X 12 = 48 pts
Conclusion: 20 pts
Circuits p 12
A1 Conceptual Physics
Spring 2013
Circuits
Chapters 34 & 35
Circuits Review Sheet: DUE BEFORE TEST
1. I have two bulbs [ 2 Ω and 3Ω] in series connected to a battery of 10V
a. What is the equivalent resistance? [5Ω]
b. What is the current? [2 A]
c. What is the voltage drop across each resistor? [4V, 6V]
d. What is the power across each resistor? [8 W, 12W]
e. If I add a 1Ω resistor in series
i. Does the equivalent resistance increase or decrease? [Increase
to 6 Ω]
ii. Does the current increase or decrease? [ Decrease to 1.67A]
iii. What happens to the voltage drop across each resistor? [ Drops
3.33 V, 5V and 1.66V]
2. I have two bulbs of [ 2 Ω and 3Ω] in Parallel connected to a battery of 10 V.
a. What is the equivalent resistance? [1.2 Ω]
b. What is the total current? [8.33 A]
c. What is the current through each resistor? [5A, 3.33 A]
d. What is the voltage drop across each resistor? [10V]
e. What is the power across each resistor? [50 W, 33.3W]
f. If I add a 1Ω resistor in Parallel
i. Does the equivalent resistance increase or decrease? [Decrease
0.545 Ω]
ii. Does the current increase or decrease? [ Increase to 18.33A]
iii. What happens to the voltage drop across each resistor? [ Same:
10V]
3. Calculate the current of a lightning bolt that delivers a charge of 35 coulombs to
the ground in a time of 1/1000 second. [35,000 A]
4. The current through a bulb connected across the terminals of a 120 volt outlet
is 0.5 A. At what rate does the bulb convert electric energy to light? [60 W]
5. An automobile headlight with a resistance of 30Ω is placed across a 12 V
battery. What is the current through the circuit? [0.4 A]
6. A motor with an operating resistance of 32Ω is connected to a voltage source.
The current in the circuit is 3.8 A. What is the voltage of the source? [121.6 V]
7. A 75 W lamp is connected to 120 V.
a. How much current flows through the lamp? [.625 A]
b. What is the resistance of the lamp? [192 Ω]
8. A 12V automobile battery is connected to an electric starter motor. The current
through the motor is 210 A.
a. How many joules of energy does the battery deliver to the motor each
second? [2520 J/s]
b. What power does the motor use in watts? [2520 W]
9. If three identical lamps are connected in series to a 6 volt battery, what is the
voltage drop across each lamp? [2V]
10. Calculate the current in a 48 V battery that powers a pair of 30 Ω resistors
connected in series. [0.8 A]
11. As more and more lamps are connected in series to a battery, what happens to
the brightness of each lamp?
12. A string of holiday lights has ten bulbs with equal resistances connected in
series. When the string of lights is connected to a 120 V outlet, the current
through the bulbs is 0.06 A.
a. What is the equivalent resistance of the circuit? [2000 Ω]
Circuits p 13
A1 Conceptual Physics
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Spring 2013
Chapters 34 & 35
b. What is the resistance of each bulb? [200 Ω]
13. Three resistors of 3.0 k Ω resistor (3.0 x 103 Ω ), 5.0 k Ω resistor, and 4.0 k Ω
resistor are connected in series across a 12 V battery.
a. What is the equivalent resistance? [12,000 Ω]
b. What is the current through the resistors? [0.001 A]
c. What is the voltage drop across each resistor? [3 V, 5V, 4V]
d. Find the total voltage drop across the three resistors. [12 V]
14. A 20.0 Ω lamp and a 5.0 Ω lamp are connected in series and placed across a
difference in potential of 50 V.
a. What is the equivalent resistance of the circuit? [25 Ω]
b. What is the current in the circuit? [2A]
c. What is the voltage drop across each lamp? [40 V, 10V]
d. What is the power used in each lamp? [80 W, 20W]
15. The load across a 12 V battery consists of a series combination of three
resistors of 15 Ω , 21 Ω , and 24 Ω .
a. What is the total resistance of the load? [60 Ω]
b. What is the current in the circuit? [0.2A]
c. What is the voltage drop across each resistor? [3V, 4.2V, 4.8V]
16. Two resistors are wired in series. In another circuit, the same two resistors are
wired in parallel. In which circuit is the equivalent resistance greater?
17. A 5Ω, 10Ω, and a 15Ω resistor are connected in series.
a. Which resistor has the most current in it?
b. Which resistor has the largest potential difference across it?[15Ω]
18. A 5Ω, 10Ω, and a 15Ω resistor are connected in parallel.
a. Which resistor has the most current in it? [5Ω]
b. Which resistor has the largest potential difference across it?
19. Three 15Ω resistors are connected in parallel and placed across a 30V potential
difference.
a. What is the equivalent resistance of the parallel circuit? [ 5Ω]
b. What is the current through the entire circuit? [6A]
c. What is the current through each branch of the circuit? [2A, 2A, 2A]
20. A 12Ω and a 15Ω resistor are connected in parallel and placed across the
terminals of a 15V battery.
a. What is the equivalent resistance of the parallel circuit? [6.7 Ω]
b. What is the current through the entire circuit? [2.25 A]
c. What is the current through each branch of the circuit? [1.25 A, 1A]
21. Three resistors: R1 = 1Ω, R2=2Ω and R3=3Ω
a. If resistors are in Series: Draw and compute the Equalivent resistance. [ 7Ω]
b. If they are in Parallel: Draw and compute Equlivant Resistance: [0.546Ω]
c. Would placing an R4 in series increase or decrease the equlivalent
resistance? [Increase]
d. Would placing an R4 in parallel increase or decrease the equlivalent
resistance? [Decrease]
e. Which configuration yields the smallest current?
22. A 19Ω resistor is connected in series to a 45V battery and two 12Ω resistors
that are connected in parallel to each other.
a. What is the equivalent resistance of the three resistors? [25Ω]
b. What is the current in the circuit? [1.8 A]
c. What is the current through the 19 Ω resistor? [1.8 A]
d. What is the current through one of the 12Ω resistors? [0.9 A]
e. What is the potential difference across the 19Ω resistor? [34.2 V]
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Spring 2013
Chapters 34 & 35
f. What is the potential difference across either 12 Ω resistor?
23. Resistors R1, R2, and R3 have resistances of 37 Ω, 22 Ω and 41 Ω respectively. R1
and R2 are connected in series, and their combination is in parallel with R3.
This arrangement is then placed across a 60V battery. Draw the circuit
diagram.
a. What is the equivalent resistance (R12) of R1 and R2? [59Ω]
b. How are R12 and R3 connected? Parallel or Series?
c. What is the equivalent resistance of the three resistors (R123 or Req)?
[24.19 Ω]
d. d. What is the size of the circuit breaker required to run this circuit
safely? [2.48A]
e. e. What is the voltage drop across the 22Ω resistor, R2? [22.44 V]
24. Three resistors are connected in parallel (2Ω, 3Ω, 4Ω), and are connected in
series to a 1Ω resistor. The entire circuit is connected to a 9V generator.
a. What is the total resistance of the circuit? [1.92 A]
b. What is the total current running through the circuit? [4.68 A]
c. What is the current in the 1Ω resistor? [4.68 A]
d. What is the voltage drop across the 3Ω resistor? [4.32 V]
e. What is the minimum sized circuit breaker needed to run this circuit
safely? [5A]
f. If you added another resistor in series with the 1Ω resistor, would the
circuit breaker trip?
25. Two resistors (R1=12Ω and R2=15Ω) are connected in series to a 90V generator.
They are also connected in parallel to two additional resistors (R3=11Ω and
R4=20Ω) which are connected to each other in series.
a. What is the Equivalent Reistance of R1 and R2. [27 Ω]
b. What is the Equivalent Resistance of R3 and R4: [31 Ω]
c. What is total resistance of the circuit? [14.43Ω]
d. What is the total current running through the circuit? [6.24 A]
e. What is the current in the 12Ω resistor? [3.33A]
f. What is the voltage drop across the 20Ω resistor? [58V]
26. Draw circuit diagrams for the following circuits.
a. Three 20Ω resistors connected in series across a 120V generator.
b. A 12Ω and a 15Ω resistor are connected in parallel and placed across
the terminals of a 15V battery.
c. Two 60Ω resistors are connected in parallel. This parallel arrangement
is connected in series with a 30Ω resistor. The entire circuit is then
placed across a 120V potential difference.
27. A 4Ω and an 8Ω resistor are connected in series. This series arrangement is
connected in parallel with a 17Ω resistor. The entire circuit is placed across a
90V potential difference.
a. Two 5Ω resistors are connected in series. This series arrangement is
connected to two 5Ω resistors connected in parallel. The parallel
arrangement is then connected in series to two more 5Ω resistors, and
the entire circuit is placed across a 120V potential difference.
b. A 2Ω and a 6Ω resistor are connected in series, and their combination is
in parallel with a 12Ω resistor to form a load across a 6V battery.
28. A 4Ω and an 8Ω resistor are connected in series. This series arrangement is
connected in parallel with a 17Ω resistor. The entire circuit is placed across a
90V potential difference.
Circuits p 15