Download ch 8 outline - Huber Heights City Schools

Electricity and Magnetism Outline
Physics Chapter 8
Part I: Electrostatics
I. Electric Charge
A. Properties of Electric Charge
1. Describe the two types of electric charge.
2. Describe how an object becomes charged.
3. What is the charge on a proton, neutron, and electron?
B. Transfer of Electric Charge
1. Conductor:
2. Insulator:
3. Semiconductor:
4. Superconductor:
5. Explain why plastic wrap is used to cover food containers.
6. Induction:
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II. Electric force
A. Electric force:
B. What did Coulomb find in his experiments?
Coulomb’s Law
C. kC (Coulomb’s constant):
Example 1: The electron and proton of a hydrogen atom are separated, on average, by a distance of
about 5.3 x 10-11 m. Find the magnitudes of the electric force and the gravitational force that each
particle exerts on the other.
Example 2: Sphere A, with a charge of +6.0 µC, is located near another charged sphere B. Sphere B
has a charge of -3.0 μC and is located 4.0 cm to the right of sphere B. What is the force between the
two spheres?
D. Describe the difference between electrical force and gravitational force.
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Set 8A
1. A balloon is rubbed against denim and gains a charge of -8.0 μC and the denim now has a charge
of +8.0 μC. What is the electric force between the balloon and the denim when the two are
separated by a distance of 5.0 cm?
2. Two identical conducting spheres are placed so that they are 0.30 cm apart. One is given a charge
of 12.0 x 10-9 C and the other is given a charge of -18.0 x 10-9 C. Find the electric force exerted on
one sphere by the other.
3. A small cork with an excess charge of 6.0 μC is placed 0.12 m from another cork, which carries a
charge of -4.3 μC.
a. What is the electric force between the corks?
b. How many excess electrons are on the negative cork?
c. How many electrons has the positive cork lost?
4. Two electrostatic point charges of 60.0 μC and 50.0 μC exert a repulsive force on each other of 175
N. What is the distance between the two charges?
III. The Electric Field
A. Electric field:
B. What does the strength of the electric field depend upon?
Electric Field Strength from a Point Charge
C. Describe how a microwave works.
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Example 3: An electric field around a charged object is 5.95 x 106 N/C at a distance of 10.0 cm. Find
the charge on the object.
Example 4: A charge q1 = 4.50 C experiences an attractive force of 1.35 N at a distance of 15.0 cm
from a charge object, q2. Find the strength of the electric field due to q2 at a distance of 15.0 cm.
Set 8B
1. A proton and an electron are separated by a distance of 5.3 x 10-11 m. What is the electric field set
up by the proton at the position of the electron?
2. What is the strength of the electric field at a position that is 1.2 m from a point charge of 4.2 x 10-6
C?
3. What is the electric field at a position that is 1.6 m east of a point charge of 7.2 x 10-6 C?
4. The electric field that is 0.25 m from a small sphere is 450 N/C toward the sphere. What is the
charge on the sphere?
5. How far must a point charge of 2.4 x 10-6 C must a test charge be placed to measure a field with a
strength of 460 N/C?
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Part II: DC Electricity
I. Electric Current
A. Current:
Electric Current
B. Units:
Example 5: The current in a light bulb is 0.835 A. How long does it take for a total charge of 1.67 C
to pass a point in the wire?
Example 6: A 100.0 W light bulb draws 0.83 A of current. How long does it take for 1.9 x 1022
electrons to pass a given cross-sectional area of the filament?
C. What is the charge on electric currents?
Set 8C
1. If a current in a wire of a CD player is 5.00 mA, how long would it take for 2.00 C of charge to
pass a point in the wire?
2. In a particular television tube, the beam current is 60.0 μA. How long does it take for 3.75 x 1014
electrons to strike the screen?
3. If a metal wire carries a current of 80.0 mA, how long does it take for 3.00 x 1020 electrons to pass
a given cross-sectional area of the wire?
4. The compressor on an air conditioner draws 40.0 A when it start up. If the start-up time is 0.50 s,
how must charge passes a cross-sectional area of the circuit in this time?
8C problem set continued on next page:
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5. A total charge of 9.0 mC passes through a cross-sectional area of a nichrome wire 3.5 s.
a. What is the current in the wire?
b. How many electrons pass through the cross-sectional area in 10.0 s?
c. If the number of charges that pass through the cross-sectional area during this given
time interval doubles, what is the resulting current?
II. Resistance
A. Resistance:
Resistance
B. Units
C. Ohm’s Law:
Example 7: The resistance of a steam iron is 19.0. What is the current in the iron when it is
connected across a potential difference of 120 V?
Set 8D
1. A 1.5 V battery is connected to a small light bulb with a resistance of 3.5 Ω. What is the current in
the bulb?
2. A stereo with a resistance of 65 Ω is connected across a potential difference of 120 V. What is the
current in this device?
8D problem set continued on next page:
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3. Find the current in the following devices when they are connected across a potential difference of
120 V.
a. A hot plate with a resistance of 48 Ω.
b. A microwave oven with a resistance of 20 Ω.
4. The current in a microwave oven is 6.25 A. If the resistance of the oven’s circuitry is 17.6 Ω, what
is the potential difference across the oven?
5. A typical color television draws 2.5 A of current when connected across a potential difference of
115 V. What is the resistance of the television set?
6. The current in a certain resistor is 0.50 A when it is connected to a potential difference of 110 V.
What is the current in this same resistor if
a. The operating potential difference is 90.0 V?
b. The operating potential difference is 130 V?
III: Circuit Diagrams
A. Schematic diagram:
B. How is it that schematic diagrams can be read and understood by anyone?
C. What is the importance of a schematic diagram?
wire:
D. Draw the symbol for each of the following components in a schematic diagram:
resistor :
bulb or lamp:
plug:
battery:
open switch:
closed switch:
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E. Closed circuit:
F. Open circuit:
G. Short circuit:
H. Why are short circuits dangerous?
IV: Series circuits
A. Series circuit:
B. What happens to the current in a series circuit?
C. Equivalent resistance:
D. What is the importance in finding the equivalent resistance?
Equivalent Resistance in a Series Circuit
E. The equivalent resistance of a series combination of resistors is:
F. To find the total current in a series circuit:
G. What happens to a series circuit when a single bulb burns out?
H. Give three reasons why you would arrange resistors in series.
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Example 8: A 9.0 V battery is connected to four light bulbs as shown. Find the equivalent resistance
for the circuit and the current in the circuit.
5.0 
2.0 
7.0 
4.0 
9.0 V
Set 8E
1. A 12.0 V storage battery is connected to three resistors: 6.75 Ω, 15.3 Ω, and 21.6 Ω. The resistors
are joined in series
a. Calculate the equivalent resistance.
b. What is the current in the circuit?
2. A 4.0 Ω resistor, an 8.0 Ω resistor, and a 12.0 Ω resistor are connected in series with a 24.0 V
battery.
a. Calculate the equivalent resistance.
b. Calculate the current in the circuit.
c. What is the current in each resistor?
3. A series combination of two resistors, 7.25 Ω and 4.03 Ω are connected to a 9.00 V battery.
a. Calculate the equivalent resistance.
b. Calculate the current in the circuit.
c. What is the potential difference across each resistor?
4. A 7.0 Ω resistor is connected in series with another resistor and a 4.5 V battery. The current in the
circuit is 0.60 A. Calculate the value of the unknown resistance.
5. Several light bulbs are connected in series across a 115 V source.
a. What is the equivalent resistance if the current in the circuit is 1.70 A?
b. If each light bulb has a resistance of 1.50 Ω, how many light bulbs are in the circuit?
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V: Parallel circuits
A. Parallel circuit:
B. What happens to the current in a series circuit?
C. If one bulb in a parallel circuit has less resistance:
Equivalent Resistance in a Parallel Circuit
D. This equation does not give the value of the equivalent resistance directly. You must:
E. The equivalent resistance for a parallel arrangement of resistors must always be:
F. What happens when a bulb burns out in a parallel circuit?
G. Why are houses wired in parallel?
Circuit Type
Schematic diagram
Series
Parallel
Current (I)
Potential Difference (V)
Equivalent Resistance (Ω)
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Example 9: A 9.0 V battery is connected to four resistors. Find the equivalent resistance for the
circuit and the total current in the circuit.
7.0Ω
4.0Ω
9.0 V
5.0Ω
2.0Ω
Example 10: Find the equivalent resistance, the current in each resistor, and the current drawn by the
circuit load for a 9.0 V battery connected in parallel to three 30.0  resistors.
Set 8F
1. The potential difference across the equivalent resistance in Example 9 equals the potential
difference across each of the individual parallel resistors. Calculate the value for the current in
each resistor.
2. A 4.0 Ω resistor, an 8.0 Ω resistor, and a 12.0 Ω resistor are connected in parallel across a 24.0 V
battery.
a. What is the equivalent resistance of the circuit?
b. What is the current in each resistor?
3. An 18.0 Ω, 9.00 Ω, and 6.00 Ω resistors are connected in parallel to a battery. A current of 4.00 A
is in the 9.00 Ω resistor.
a. Calculate the equivalent resistance of the circuit.
b. What is the potential difference across the source?
c. Calculate the current in the other resistors.
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VI: Complex Circuits
A. How does your house prevent excessive current?
B. Fuse:
C. Circuit breaker:
D. What would happen if all the appliances were used at once?
E. How do you determine the equivalent resistance for a complex circuit?
Example 11: Find the equivalent resistance of the complex circuit shown.
6Ω
6Ω
2Ω
2Ω
4Ω
3Ω
9V
Set 8G
**8G Worksheet**
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Part III: Magnetism
I: Magnetism
A. Describe the different parts of a magnet.
B. What happens when two magnets are brought near one another?
C. What is the difference between magnetic poles and electric?
D. What happens when a bar magnet is cut in half?
E. Which materials are the best magnets?
F. Magnetic field:
G. How do you draw magnetic field lines?
II: Electromagnetism
A. In 1820, Hans Christian Oersted discovered:
B. Induced current:
C. Generator:
D. Describe how a generator works.
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