Download Physics I REVEW SHEET: Circuits Due FRIDAY, March 11 START of

Physics I REVEW SHEET: Circuits
Due FRIDAY, March 11 START of class
1. 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]
2. 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? [60 W]
3. 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]
4. 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]
5. 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]
6. 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]
7. If three identical lamps are connected in series to a 6 volt battery, what is the voltage drop across each lamp?
[2V]
8. Calculate the current in a 48 V battery that powers a pair of 30 Ω resistors connected in series. [0.8 A]
9. As more and more lamps are connected in series to a battery, what happens to the brightness of each lamp?
10. 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]
11. 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]
12. 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]
13. 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]
14. 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?
15. 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]
16. 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?
17. 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]
18. 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]
19. 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?
20. 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]
f. What is the potential difference avross either 12 Ω resistor?
21. Resistors R1, R2, and R3 have resistances of 37 Ω, 22 Ω and 41 Ω respectively. R 1 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 eqalivant resitance (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]
22. 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?
23. 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]
24. 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.
25. 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.
26. 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.