Transcript Chapter 17 & 18

CHAPTER 17 – QUESTIONS 1-3
1. Describe how charged objects interact by using the law of electric
charges. Positives are attracted to negatives.
2. Describe 3 ways in which an object can become charged.
Friction: rubbing electrons from one surface to another;
Conduction: electrons move by direct contact; Induction:
Electrons move and become charged WITHOUT touching!
3. Compare conductors with insulators. Conductor allow electrons
to move FREELY; Insulators prevent electrons from moving.
CHAPTER 17 - QUESTIONS 4-6
4. Give 2 examples of static electricity and electric discharge. Static
Electricity: built up charges in clothing in a dryer and dragging your
feet on the carpet. Electric discharge: Lightning and shocking
yourself on a doorknob
5. What are the 2 types of charged particles in atoms? Protons and
Electrons
6. What can you do with an electroscope? See if an object is
charged.
CHAPTER 17 – QUESTIONS 7-9
7. What is electric discharge? The release of electricity
moving from one object to another.
8. Why is it dangerous to be outside in an open area
during a storm? Lightning usually strikes the highest
object in an area.
9. Describe electric current. How quickly a charge passes
through a wire; measured in AMPS!
CHAPTER 17 - QUESTIONS 10-12
10. Describe voltage and its relationship to electric
current. The size of an electric current depends on
how much voltage is applied. More voltage = more
current!
11. Describe resistance and its relationship to electric
current. More resistance = less current and vice
versa!
12. Explain how a cell generates electrical energy.
Converts chemical energy to electrical energy (like a
battery).
CHAPTER 17 - QUESTIONS 13-15
13. Describe how thermocouples and photocells
generate electrical energy. Thermocells change heat
(thermal energy) into electrical energy; Photocell
convert light energy into electrical energy.
14. What is the unit of measurement for electric current?
Amperes (AMPS)
15. What are 2 kinds of electric current? AC (Alternating
Current) and DC (Direct Current)
CHAPTER 17 - QUESTIONS 16-18
16. What is the unit of measurement for
voltage? volts
17. What are the 2 kinds of cells? wet and dry
18. What device converts light energy into
electrical energy? photocell
CHAPTER 17 - QUESTIONS 19-21
19. What is the formula for calculating Ohm’s Law? What do each of
the letters represent? R (Resistance) = V (Voltage)/I (Current) or
V(Voltage) = I (Current) X R(Resistance); unit is the ohm (Ω)
20. What is the formula for calculating electric power? What do each
of the letters represent? P (Power) = V (Voltage) X I (Current); unit
is watt or kilowatt
21. What are 2 common units for electric power? Watt or Kilowatt
CHAPTER 17 - QUESTIONS 22-24
22. What is the formula for calculating electrical energy?
What do each of the letters represent? E (Electrical
Energy) = P(Power) X t (Time)
23. What unit of measurement is usually used to express
electrical energy? Kilowatt-hours (kWh)
24. A computer monitor draws 1.2 A at a voltage of 120
V. What is the power rating of the monitor? 144W
CHAPTER 17 - QUESTIONS 25-27
25. A light bulb draws a 0.5 A current at a voltage of 120
V. What is the power rating of the light bulb? 60W
26. How much electrical energy does a 100 W light bulb
use if it is left on for 24 hours? 2.4 kWh
27. Name the 3 essential parts of a circuit. Energy
source, wires, and a load
CHAPTER 17 - QUESTIONS 28-30
28. Illustrate a series circuit and a parallel circuit.
Series
Parallel
Circuit
Circuit
29. Compare series circuits with parallel circuits. In a Series circuit all parts are
connected in ONE SINGLE LOOP. In a Parallel Circuit parts are connected
SIDE BY SIDE, so if part of the circuit stops working the charges still flow.
Explain how fused and circuit breakers protect your home against short
circuits and circuit overloads. A fuse has a thin strip of metal that expands
and contracts in the presence of current. If the current is too high, the metal
strip melts and the circuit is broken – preventing electrical fires. Circuit
Breakers are switches that automatically open with the current is too high. If
there is not a connection, current cannot flow. Therefore it prevents
electrical fires as well.
30. How are loads connected in a series circuit? In a single loop or straight line.
CHAPTER 17 - QUESTIONS 31-32
31. How are loads connected in a parallel circuit? Side by side
32. What are 2 safety devices used in circuits? Fuses and Circuit
Breakers
CHAPTER 18 - QUESTIONS 1-3
1. Describe the properties of magnets. 2 poles, exert magnetic force,
surrounded by magnetic field
2. Explain why some materials are magnetic and some are not. The
arrangement of the atoms (called domains) determine whether an
object is magnetic or not.
3. Describe 4 kinds of magnets.
Ferromagnets – made of iron, nickel, cobalt, etc.
Electromagnets – magnet made by an electric current
Temporary Magnets – made from materials that are easy to
magnetize –
lose magnetism easily
Permanent Magnets – difficult to magnetize, but keep magnetism
indefinitely
CHAPTER 18 - QUESTIONS 4-6
4. Give 2 examples of the effect of Earth’s magnetic
field. Poles like a compass needle, Spinning electrons
cause movement ; magnetic field
5. If 2 magnets push each other away, what can you
conclude about their poles? They carry the same
charge.
6. Why are copper and aluminum not magnetic? Their
atomic structure does not allow for it.
CHAPTER 18 - QUESTIONS 7-9
7. Describe 2 ways a magnet can lose its magnetic
properties. Striking it or heating it
8. What are ferromagnets? Magnets made with iron,
nickel, or cobalt
9. What do scientists think causes Earth’s magnetic
field? The movement of electric charges at Earth’s
solid inner core (made of iron and nickel).
CHAPTER 18 - QUESTIONS 10-12
10. Identify the relationship between an electric current and a magnetic
field. A current carrying wire causes a magnet to move.
11. Compare solenoids and electromagnets. Solenoids: a coil of wire with
an electric current running through it. Electromagnet: a magnet that has
an electric current attached that can be switched on and off. A solenoid
is part of an electromagnet.
12. Describe how electromagnetism is involved in the operation of
doorbells, electric motors, and galvanometers. An electric current moves
in a solenoid that is attached to a magnetic material . This allows the
electric current to move so your doorbell rings, motor runs, and
galvanometer to measure the movement.
CHAPTER 18 - QUESTIONS 13-15
13. What is electromagnetism? The interaction between electricity
and magnetism.
14. What happens to the magnetic field of an electromagnet if you
increase the current in the wire? The field gets bigger or
stronger.
15. Why does a current carrying wire cause a compass needle to
move? The electric current creates a magnet field that exerts a
force on the compass needle and causes it to move.
CHAPTER 18 – QUESTIONS 16-18
16. What does a galvanometer measure? Current
17. Explain how a magnetic field can make an electric current. The
movement in a magnetic field induces (makes it move without
touching it) an electric current.
18. Explain how electromagnetic induction is used in a generator.
Electromagnetic induction is used to change mechanical energy
to electrical energy.
CHAPTER 18 – QUESTIONS 19-21
19. Compare step-up and step-down transformers. Stepup increase voltage; Step-down decreases voltage.
20. What was Faraday trying to do in his experiment?
Prove that an electromagnet could induce an electric
current.
21. What energy change happens in an electric
generator? Changes mechanical energy to
mechanical energy.
CHAPTER 18 – QUESTIONS 22-23
22. What are 3 sources of energy that are used to
generate electrical energy? Nuclear reaction, fossil
fuels, and wind.
23. What does a transformer do? Increases or decreases
the voltage of an alternating current.
24. What is AC and DC? AC = Alternating Current –
current travelling in both directions. DC = Direct
Current – current travelling in one direction.