Download Electricity and Magnetism

Name______________________________
HW - E1
Pts (20)
Quiz - Elec.
Pts (25)
Electricity & Magnetism
Lab – Circuit
Pts (25)
HW - M1
Pts (10)
Quiz - Mag.
Pts (15)
Electric Motor
Project
Pts (100)
Test - Electricity and
Magnetism
Pts (33)
Date
Due
By the end of this unit, you should be able to:
• PS-6.5 Explain how objects can acquire a static electric charge through friction, induction, and conduction.
• PS-6.6 Explain the relationships among voltage, resistance, and current in Ohm’s law.
• PS-6.7 Use the formula V = IR to solve problems related to electric circuits.
• PS-6.8 Represent an electric circuit by drawing a circuit diagram that includes the symbols for a resistor, switch, and voltage source.
• PS-6.9 Compare the functioning of simple series and parallel electrical circuits.
• PS-6.10 Compare alternating current (AC) and direct current (DC) in terms of the production of electricity and the direction of current flow.
• PS-6.11 Explain the relationship of magnetism to the movement of electric charges in electromagnets, simple motors, and generators.
Electricity (Chapter 7) - Notes
Section 1 Electric Charge
A. Protons have ____________ electric charge; electrons have ____________ electric charge.
1. In most atoms, the charges of the protons and electrons cancel each other out and the atom has no net charge.
2. Atoms become charged by gaining or losing electrons.
3. Static electricity—the accumulation of excess electric charge on an object
4. If a substance gains electrons, it becomes _______________ charged.
5. If a substance loses electrons, it becomes ________________ charged.
B. Electrically charged objects obey the following rules:
1. Law of conservation of charge—charge may be transferred from object to object, but it cannot be created or destroyed.
2. Opposite charges attract, and like charges repel.
3. Charges can act on each other even at a distance, because any charge that is placed in an electric field will be
pushed or pulled by the field.
4. Electrons move more easily through conductors, like metals.
5. Electrons do not move easily through insulators, such as plastic, wood, rubber, and glass.
C. Transferring electric charge
1. Charging by ___________
a. The process of transferring charge by touching or rubbing
b. Ex: static electricity from your feet rubbing the carpet
2. Charging by _____________
a. The rearrangement of electrons on a neutral object caused by a nearby charged object
b. Ex: a negatively charged balloon near a sleeve causes an area of the sleeve to become positively charged
3. Static _____________
a. A transfer of charge through the air between two objects because of a build-up of static electricity
b. Example: lightning
4. Grounding—using a _____________ to direct an electric charge into the ground
D. The presence of electric charges can be detected by an ________________.
Section 2 Electric Current
A. The flow of charges through a wire or conductor is called electric ___________.
1. Current is usually the flow of _____________
2. Electric current is measured in amperes (A).
3. Charges flow from high voltage to low voltage.
a. A voltage difference is the push that causes charges to move.
b. Voltage difference is measured in volts (V).
4. For charges to flow, the wire must always be connected in a closed path, or ________________.
B. _____________ of electricity:
1. A dry cell battery produces a voltage difference between its zinc container
and its carbon suspension rod, causing current to flow between them.
2. A wet cell battery contains two connected plates made of different metals in
a conducting solution.
3. Wall sockets have a voltage difference across the two holes of an electrical
outlet, and a generator at a power plant provides this voltage difference.
C. Direct and Alternating Currents
1. _____________ current – the flow of electrons is in only one direction through the wire.
Ex: battery
2. _____________ current – the flow of electrons reverses in direction in a regular pattern.
Ex: wall outlet / produced by generator
D. Resistance—the tendency for a material to oppose the flow of electrons, changing electrical energy
into ___________ energy and _________
1. All materials have some electrical resistance.
2. Resistance is measured in ohms (Ω).
3. Making wires thinner, longer, or hotter increases the resistance.
E. Ohm’s law—the current in a circuit equals the voltage difference divided by the _________
Section 3 Electrical Circuits
A. Circuits rely on _____________ at power plants to produce a voltage difference across the
outlet, causing the charge to move when the circuit is complete.
1. Series circuit—the current has only one ________ to flow through
a. The parts of a series circuit are wired one after another, so the amount of current is the
same through every part.
b. Open circuit—if any part of a series circuit is disconnected, no current flows through the circuit
c. Ex: strings of Christmas tree lights
2. Parallel circuit—contains two or more ____________ for
current to move through
a. Individual parts can be turned off without
affecting the entire circuit.
b. Ex: the electrical system in a house
B. Household circuits use ____________ circuits connected in a logical network.
1. Each branch receives the standard voltage difference from the electric company.
2. Electrical energy enters your home at the circuit breaker or fuse box and branches
out to wall sockets, major appliances, and lights.
3. Guards against overheating electric wires:
a. Electrical fuse—contains a small piece of metal that melts if the current
becomes too high, opening the circuit and stopping the flow of current
b. Circuit breaker—contains a small piece of metal that bends when it gets
hot, opening the circuit and stopping the flow of current
C. Electrical energy is easily converted to mechanical, thermal, or _________ energy.
1. Electrical power—the rate at which electrical energy is converted to another form of energy
a. Electrical power is expressed in watts (W).
b. Power = current x voltage difference
c. P (watts) = I (amperes) x V (volts)
2. To calculate the amount of energy an appliance uses:
a. The unit of electrical energy is the kilowatt-hour, which equals 1000 watts of power
used for one hour.
b. Energy = power x time
c. E (kWh) = P (kW) x t (hr.)
Name_________________________________
Date_____________________
Score______________/20
Electricity HW (E1)
1. List the 3 particles of an atom and identify their charges.________________________________________________
__________________________________________________________________________________________________
2. Which of the following is true about two adjacent electric charges?
A. If both are (+), they attract
B. If both are (-), they attract
C. If one is positive and one is negative, they attract
D. If one is positive and one is negative, they repel
3. Explain how an electrically neutral object can become electrically charged._________________________________
__________________________________________________________________________________________________
4-5. This electroscope is positively charged.
What would happen to the metal leaves if a negatively charged
rod is touched to the knob of the electroscope?
+
+
A. The leaves will not move.
B. The leaves will move closer together.
C. The leaves will move further apart.
D. The electroscope will become negatively charged.
+
+
What would happen to the metal leaves if a positively charged
Rod is touched to the knob of the electroscope?
+
+
+
A. The leaves will not move.
B. The leaves will move closer together.
C. The leaves will move further apart.
D. The electroscope will become negatively charged.
6. Describe how lightning is produced:__________________________________________________________________
__________________________________________________________________________________________________
7-9. Relate voltage, current, and resistance of an electrical circuit to the working of a water hose.
Voltage
Current
Resistance
A water hose
“the pressure of the water”
“the flow of the water
“anything that slows the
through the hose”
flow of water”
An electrical circuit
10. Identify two ways to increase the current in a simple circuit._____________________________________________
11. Resistance in wires causes electrical energy to be converted into which form of energy?
A. chemical energy
B. nuclear energy
C. thermal energy
D. sound
V = IR
P = IV
V = voltage (volts)
I = current (amps)
R = resistance (ohms Ω)
P = power (watts)
12. Explain how the resistance of a light bulb filament changes after the light has been turned on. (p. 204)
__________________________________________________________________________________________________
13-14. Draw a series circuit with a battery & 1 light bulb.
Draw a parallel circuit with 3 loops, 3 light bulbs & 1 battery.
Draw the electron flow of current out of the batteries of each circuit.
15-16. Draw a simple series circuit, with a battery, a light bulb with a resistance of 25 Ω, and a current of 0.5 A.
CALCULATE THE VOLTAGE IN THIS CIRCUIT. (Show your work.)
17. A current of 0.5 Amps flows in a 60-Watt light bulb when the voltage difference between the ends of the filament
is 120 V. What is the resistance of the filament? (Show your work.)
18. A DVD player that is not playing, still uses 10.0 W of power. What is the current in the DVD player if it is plugged
into a 120-V outlet? (Show your work.)
19-20. The table show the current in circuits that were each connected to a 6-V dry cell.
 Calculate the resistance of each circuit.
Circuit
Current (A)
 Graph the current versus the resistance of each circuit.
A
2.3
 Describe the shape of your line.
B
0.6
C
0.2
D
1.8
The BIG idea!
Magnetism is related to the movement of electric charges in electromagnets,
simple motors, and generators.
Magnetism (Chapter 8) - NOTES
A. Interaction between two magnets called _____________________ increases as magnets move closer together.
Magnetic ______________, which
exert magnetic force, surround a
magnet, and are strongest closest
to the magnet.
___________________—the
regions of a magnet where the
magnetic force exerted by the
magnet is strongest
B. Magnetic materials—_______________________
- Permanent magnets are made by placing a
magnetic material in a strong magnetic field,
forcing a large number of magnetic domains
to line up.
Magnetic domains—groups of
atoms with aligned magnetic poles
1. All magnets have a north pole and a south pole.
2. Like poles repel. Unlike poles attract.
3. Earth has magnetic poles.
a. A compass needle is a small bar magnet
that can freely rotate.
b. A compass needle always points north.
c. Scientists are unsure of what causes
the earth’s magnetic field.
In a magnet, the like
poles of all the
domains point in the
same direction.
Discussion: Permanent magnets can lose their magnetic properties if they are heated. Explain why
magnetic properties are lost under these conditions.
Electricity and Magnetism
A. Moving charges, like those in an electric current, produce magnetic fields.
- The strength of the magnetic field depends on the amount of current flowing in the wire.
B. __________________________—a temporary magnet made by placing a piece of iron inside a current carrying coil of wire
1. Magnetic field is present only when current is flowing in the wire coil.
2. Increase strength of the magnetic field by adding more turns to the wire coil or increasing the current passing through the wire.
3. Magnetic properties of electromagnets can be controlled by changing the electric current flowing through the wire coil.
4. Converts electrical energy into mechanical energy to do work
Name_________________________________
Magnetism HW (M1)
Date_____________
Score________/10
______1. Alternating current changes the __________ of the current flow.
A. amount
B. direction
C. strength
D. voltage
______2. In order for the electromagnetic coil in a motor to keep turning, the current must __________ .
A. flow through an ammeter
B. change direction
C. periodically increase in strength
D. continue flowing in one direction
______3. The magnetic field of an electromagnet can be increased by
A. changing the direction of the current.
B. decreasing the current.
C. increasing the number of coils.
D. decreasing the number of coils.
______4. What does this illustration represent?
A. magnetic material that is not magnetized
B. magnetic material that is magnetized
C. non-magnetic material
D. arrangement of atoms in a domain
_____5. In this illustration, the magnetic field is strongest _______.
A. near either pole
B. near the north pole
C. near the south pole
D. halfway between the poles
______6. Which of the following describes the direction of the electric current in DC?
A. The flow changes regularly.
B. The flow changes irregularly.
C. The flow shows no pattern.
D. The flow is in one direction.
______7. Which of the following best describes how electricity is generated for homes?
A. The spinning of a windmill's blades creates electric current without a generator.
B. Steam pushes turbine blades in a generator, which changes the mechanical energy into an electric current.
C. Water released from a dam generates electric current, which is transformed into mechanical energy.
D. Nuclear reactions cause electric current to flow around the reaction chamber.
______8. Which of the following elements is magnetic?
A. aluminum B. lead C. iron
D. tin
______9. When a bar magnet is broken into two pieces, each piece has a north and south pole because __________.
A. the magnetic fields reversed
B. every magnet is made of many aligned smaller magnets
C. bar magnets are permanent magnets
D. the magnetic poles have been isolated
______10. Why does the north pole of a compass point toward Earth's geographic north pole?
A. A compass does not rely on Earth's magnetic field to function.
B. Like poles attract.
C. Opposite poles repel.
D. Earth's geographic north pole is a south magnetic pole.