Ohm’s Law
1. If 0.6A current flows through unknown resistor. Potential difference between two
points of resistor is 12V. What is the resistance of the resistor?
2. Resistance of an electric iron 50 Ω.4.2A Current flows through the resistance. Find the
voltage between two points.
3. Filament resistance of an electric bulb is 660 Ω. Potential difference of two points
220V. Find the current through the filament flowing.
4. A 110volt wall outlet supplies power to a strobe light with a resistance of 2200ohms.
How much current is flowing through the strobe light?
5. A CD player with a resistance of 40 ohms has a current of 0.1 amps flowing through
it. Sketch the circuit diagram and calculate how many volts supply the CD player?
6. A CD player with a resistance of 40 ohms has a current of 0.1 amps flowing through
it. Sketch the circuit diagram and calculate how many volts supply the CD player?
7. An electric heater draws 3.5 A from a 110 V source. Calculate the resistance of the
heating element is approximately.
8. If 750 µA is flowing through 11 k of resistance, what is the voltage drop across the
resistor?
9. Approximately how many milliamperes of current flow through a circuit with a 40 V
source and 6.8 k Ω of resistance?
10. How much resistance is required to limit the current from a 12 V battery to 3.6 mA?
11. What is the voltage source for a circuit carrying 2 A of current through a 36
resistor?
12. What is the approximate resistance setting of a rheostat in which 650 mA of current
flows with a 150 V source?
13. How much voltage is needed to produce 2.5 A of current through a 200 resistor?
14. When there is 12 mA of current through a 1.2 k Ω resistor, the voltage across the
resistor is
15. When 12 V are applied across a 68 Ω resistor, the current is
16. Approximately how much current flows through a 3.3 MΩ resistor across a 30 V
source?
17. A 120 V lamp-dimming circuit is controlled by a rheostat and protected from
excessive current by a 3 A fuse. To what minimum resistance value can the rheostat
be set without blowing the fuse? Assume a lamp resistance of 20 ohms.
18. What is the approximate filament resistance of a light bulb if it operates from a 110
V source and 0.6 A of current is flowing?
19. What is the approximate resistance of a rheostat if the voltage source is 18 V and the
current is 220 mA?
Series Circuits - General Questions
1. When a fourth resistor is connected in series with three resistors, the total resistance.
2. A string of five series resistors is connected across a 6 V battery. Zero voltage is
measured across all resistors except R3. The voltage across R3 is
3. A series circuit consists of three resistors with values of 120Ω, 270Ω, and 330Ω. The
total resistance is
4. A certain series circuit consists of a 1/8 W resistor, a 1/4 W resistor, and a 1/2 W
resistor. The total resistance is 1200 . If each resistor is operating in the circuit at
its maximum power dissipation, total current flow is
5. Which of the following series combinations dissipates the most power when
connected across a 120 V source?
6. When one of three series resistors is removed from a circuit and the circuit is
reconnected, the current
7. The total power in a certain circuit is 12 W. Each of the four equal-value series
resistors making up the circuit dissipates
8. The following resistors (one each) are connected in a series circuit: 470Ω, 680Ω, 1 kΩ,
and 1.2 kΩ. The voltage source is 20 V. Current through the 680 resistor is
approximately
9. A series circuit consists of a 4.7 kΩ, a 12 kΩ, and a 2.2 kΩ resistor. The resistor that
has the most voltage drop is
10. All the voltage drops and the source voltage added together in a series circuit is equal
to
11. Two resistors are in series: a 5.6 kΩ resistor and a 4.7 kΩ resistor. The voltage drop
across the 5.6 kΩ resistor is 10 V. The voltage across the 4.7 kΩ resistor is
12. Three 680Ω resistors are connected in series with a 470 V source. Current in the
circuit is
13. There are five resistors in a given series circuit and each resistor has 6 V dropped
across it. The source voltage
14. If a 6 V and a 9 V source are connected series aiding, the total voltage is
15. Five resistors are connected in a series and there is a current of 3 A into the first
resistor. The amount of current into the second resistor is
16. The total resistance of eight 5.6 kΩ resistors in series is
17. A series circuit has a 24 V source and a total resistance of 120 . The current through
each resistor is
18. To measure the current out of the second resistor in a circuit consisting of four
resistors, an ammeter can be placed
19. A 12 V battery is connected across a series combination of 68Ω, 47Ω, 220Ω, and 33Ω.
The amount of current is
20. If a 24 V and a 6 V battery are series opposing, the total voltage is
21. A series circuit consists of three resistors. Two resistors are 1.2 kΩ each. The total
resistance is 12 kΩ. The value of the third resistor
22. Four equal-value resistors are in series with a 12 V battery and 13.63 mA are
measured. The value of each resistor is
23. Two 1.5 V cells are connected series opposing across two 100Ω resistors in series.
Total current flow is
24. The total resistance of a circuit is 680Ω. The percentage of the total voltage appearing
across a 47Ω resistor that makes up part of the total series resistance is
PARALLEL CONNECTION
1. The total resistance of a parallel circuit is 50Ω. If the total current is 120 mA, the
current through the 270Ω resistor that makes up part of the parallel circuit is
approximately
2. The currents into a junction flow along two paths. One current is 4 A and the other is
3 A. The total current out of the junction is
3. When an additional resistor is connected across an existing parallel circuit, the total
resistance
4. When a 1.6 kΩ resistor and a 120Ω resistor are connected in parallel, the total
resistance is
5. If there are a total of 120 mA into a parallel circuit consisting of three branches, and
two of the branch currents are 40 mA and 10 mA, the third branch current is
6. Four equal-value resistors are connected in parallel. Ten volts are applied across the
parallel circuit and 2 mA are measured from the source. The value of each resistor is
7. A set of Christmas tree lights is connected in parallel across a 110 V source. The
filament of each light bulb is 1.8 kΩ. The current through each bulb is approximately
8. The power dissipation in each of four parallel branches is 1.2 W. The total power
dissipation is
9. A 470Ω, 220Ω and a 100Ω resistors are connected in parallel. The total resistance is
approximately
10. Five light bulbs are connected in parallel across 110 V. Each bulb is rated at 200 W.
The current through each bulb is approximately
11. Four resistors of equal value are connected in parallel. If the total voltage is 15 V and
the total resistance is 600Ω, the current through each parallel resistor is
12. Five 100Ω resistors are connected in parallel. If one resistor is removed, the total
resistance is
13. Four 8Ω speakers are connected in parallel to the output of an audio amplifier. If the
maximum voltage to the speakers is 12 V, the amplifier must be able to deliver to the
speakers
14. The following currents are measured in the same direction in a three-branch parallel
circuit: 200 mA, 340 mA, and 700 mA. The value of the current into the junction of
these branches is
15. The following resistors are in parallel across a voltage source: 220Ω, 470Ω, and
560Ω. The resistor with the least current is
16. Three 47Ω resistors are connected in parallel across a 110 volt source. The current
drawn from the source is approximately
17. There is a total of 800 mA of current into four parallel resistors. The currents through
three of the resistors are 40 mA, 70 mA, and 200 mA. The current through the fourth
resistor is
18. Four resistors are connected in parallel. Fifteen mA flows through resistor R. If the
second resistor is 2R, the third resistor 3R, and the fourth resistor 4R, the total current
in the circuit is
19. If one of the resistors in a parallel circuit is removed, the total resistance
20. Six resistors are in parallel. The two lowest-value resistors are both 1.2 kΩ. The total
resistance
21. In a five-branch parallel circuit, there are 12 mA of current in each branch. If one of
the branches opens, the current in each of the other four branches is
Energy & Power
1. A 33Ω half-watt resistor and a 330 Ω half-watt resistor are connected across a 12 V
source. Which one(s) will overheat?
2. When the pointer of an analog ohmmeter reads close to zero, the resistor being
measured is
3. A certain appliance uses 350 W. If it is allowed to run continuously for 24 days, how
many kilowatt-hours of energy does it consume?
4. A power supply produces a 0.6 W output with an input of 0.7 W. Its percentage of
efficiency is
5. A 15 V source is connected across a 12 Ω resistor. How much energy is used in three
minutes?
6. A 120 Ω resistor must carry a maximum current of 25 mA. Its rating should be at least
7. If it takes 400 ms to use 12,000 J of energy, the power is
8. How many watt-hours represent 65 W used for 18 h?
9. For 12 V and 40 mA, the power is
10. A 220 Ω resistor dissipates 3 W. The voltage is
11. A 3.3 k Ω resistor dissipates 0.25 W. The current is
12. A half-watt is equal to how many milliwatts?
13. Three hundred joules of energy are consumed in 15 s. The power is
14. The power rating of a carbon-composition resistor that is to handle up to 1.2 W
should be
15. A 75Ω load uses 2 W of power. The output voltage of the power supply is
approximately
16. When the current through a 12 kΩ resistor is 8 mA, the power is
17. A 68Ω resistor is connected across the terminals of a 3 V battery. The power
dissipation of the resistor is
Series-Parallel Circuits
1. Two 1.2 kΩ resistors are in series and this series combination is in parallel with a 3.3
kΩ resistor. The total resistance is
2. The output of a certain voltage divider is 12 V with no load. When a load is connected,
the output voltage
3. A voltage divider consists of two 68 kΩ resistors and a 24 V source. The unknown
output voltage is
4. Three 10 kΩ resistors are connected in series. A 20 kΩ resistor is connected in parallel
across one of the 10 k resistors. The voltage source is 24 V. The total current in the
circuit is
5. A certain voltage divider consists of three 1 kΩ resistors in series. Which of the
following load resistors will have the least effect on the output voltage?
6. A certain Wheatstone bridge has the following resistor values: R1 = 10 kΩ, R2 = 720 Ω,
and R4 = 2.4 k Ω. The unknown resistance is
7. The parallel combination of a 6.8 k Ω resistor and a 10 kΩ resistor is in series with the
parallel combination of a 2.2 kΩ resistor and a 1 kΩ resistor. A 100 V source is
connected across the circuit. The voltage drop across.
8. A certain circuit is composed of two parallel resistors. The total resistance is 1403 Ω.
One of the resistors is 2 kΩ. The other resistor value is
9. The parallel combination of a 470 Ω resistor and a 680 Ω resistor is in series with the
parallel combination of four 2 kΩ resistors. The total resistance is
10. A 12 kΩ resistor, a 15 kΩ resistor, and a 22 kΩ resistor are in series with two 10 kΩ
resistors that are in parallel. The source voltage is 75 V. Current through the 15 kΩ
resistor is
11. Two 3.3 kΩ resistors are in series and this series combination is in parallel with a 4.7
kΩ resistor. The voltage across one of the 3.3 kΩ resistors is 12 V. The voltage across
the 4.7 kΩ resistor is
12. A balanced Wheatstone bridge consists of an RV of 3500 Ω, an R2 of 200 Ω, and an R3
of 680 Ω. The value of RUNK is
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Mix Problems
1. A resistance of 10 is placed across a 9 V battery. What current flows through the
battery?
2. A resistor has a conductance of 0.100 S. What is its resistance?
3. What voltage is needed to cause a 500mA current to flow through the circuit?
4. What is the overall resistance of a CD portable player if it is operated by a 3 V battery
and 0.75 A flow through its circuitry?
5. A radio is designed to take in 2 A when connected to a 10-V source. What is its
net resistance?
6. A spotlight has a resistance of 20 ohms and requires 32 A of current to
function. What amount of voltage does the light need to be plugged into?
7. What charge has passed through a wire with 4 ohms of resistance if it is attached to a
3-V battery for 2 minutes?
8. A blender draws 6 A at 90-V. What current would it receive if the voltage suddenly
dropped 25%?
9. An electrical device is attached to a 200-V source and has a resistance of 16
ohms. How many electrons are leaving the electrical device per hour?
10. 4.0 × 10 electrons flow through a wire that has a resistance of 14 ohms and
is attached to a 35-V source. Hwo long has the wire between attached to the
electrical source?
11. A frying pan is connected to a 110-volt circuit. If the resistance of the frying pan is 10
ohms, how many amperes does the frying pan draw?
12. When a current of 3 amperes is run through the coiled heating element of a stove,
the resistance of the element is 80 ohms. What is the voltage of the stove?
13. A lightbulb carries 0.5 A when 4 volts is impressed across it. What is the resistance
of the filament in the lightbulb?
14. What is the voltage drop across a 120Ω resistor with a current of 1.5A through?
15. What is the current through 250Ω resistor if the voltage drop across it is 24V?
16. If the refrigerator draws 1.2A at 120V, what is its resistance?
17. The voltage drop across a 150Ω resistor is 2.5V, what is the power input to the
resistor?
18. The power input of 100Ω resistor is 50W, what is the current trough the resistor?
19. The 120V light bulb dissipated 40W power, what is the resistor of light bulb, and how
much current through the bulb?
Example 1: Find the total equivalent resistance in the
following circuit
Example 2: For the following circuit:
a. Find the total resistance
b. Find the current i
c. Find the voltage accross the 10Ω resistor
Example 3: For the following circuit:
a. Find the total resister value RT
b. Find the current i
c. Find the voltage across the individual
resistors
d. Verify Kirchhoff’s voltage law
Example 4: For the following circuit:
a. Find V1
b. Find V2
c. Verify Kirchhoff Voltage Law around a
closed loop
Example 5: For the following circuit
a.
b.
c.
d.
Find the total resister value RT
Find the current i
Find the voltage over resistors
Verify Kirchhoff’s voltage law
Example 6: Find the current for the following circuit.
Problem 1: Find following for the following circuit
Problem 2: Calculate the voltages for the following circuit.
Problem 3: Find the applied voltage to the following circuit using the information provided
Problem
4:
Find
Problem 5: Find Vx
the
resistor
R
value
using
Solution:
the
information
provided