Electricity and Magnetism

Transcription

1 Electricity and Magnetism S8P5. Students will recognize the characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. b. Demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy. c. Investigate and explain that electric currents and magnets can exert force on each other.

2 Do You Remember the Parts of an Atom? Protons Positive Charge Neutrons No Charge Electrons Negative Charge Where do we find each part?

3 Do You Remember What a Force is? PUSH or PULL

4 What is Electricity? Electricity is the energy caused by moving electrons from atom to atom.

5 The Law of Electrical Charges 2. Two particles that have the SAME charge REPEL each other. Each object exerts a force on each other pushing them apart. Two particles that have DIFFERENT charges ATTRACT each other. Each object exerts a force on each other that pulls them together.

6 How Can An Atom Be Charged? 3. Atoms have EQUAL numbers of protons and electrons. Because an atom s positive and negative charges cancel each other out, most atoms do not have a charge. So, how can anything made of atoms be charged? An object becomes POSITIVELY charged when it LOSES electrons. An object becomes NEGATIVELY charged when it GAINS electrons.

7 3 Ways Atoms Can Become Charged FRICTION CONDUCTION INDUCTION

8 The Material Matters Different MATERIALS are used because electric charges move through some materials more easily than they move through others. Most materials are either CONDUCTORS or INSULATORS based on how easily charges move in them.

9 Conductors and Insulators An electrical CONDUCTOR is a material in which charges CAN move easily. An electrical INSULATOR is a material in which charges CANNOT move easily. How is this cord using conductors and insulators to safely transfer electricity?

10 Conductor or Insulator? Insulator Insulator Conductor Conductor Conductor Conductor Conductor Insulator Insulator Insulator Are there any non-metal conductors? YES!...graphite, solutions of salts, and all plasmas What do the conductors have in common?

11 Static Electricity STATIC electricity is the electric charge at rest on an object. STATIC means NOT MOVING If the electrons aren t moving the object keeps its charge. Do the hairs on this boys head have the same electric charges? Does the laundry have the same electric charge as the clothing the girl is wearing?

12 Static Electricity Continued Clothing in the dryer is charged by. A. Friction B. Conduction C. Induction Negative As clothing tumbles charges are transferred. A. Positive B. Negative C. Neutral an Insulator Because clothing is, the built-up electric charges stay on each piece of clothing. A. an Insulator B. a Conductor Friction

13 Electric Discharge Charges that build up as static electricity on an object eventually leave the object. The loss of static electricity as charges move off an object is called ELECTRIC DISCHARGE. Sometimes, electric discharge happens quickly. It may happen with a flash of light, a shock, or a crackling noise.

14 LIGHTNING is an Electric Discharge

15 Electric Current An electric CURRENT is the rate at which charges pass a given point. The higher the current is, the greater the number of charges that pass the point each second. Electric current is expressed in units called amperes, which is often shortened to amps. Low Amps Back to Voltage High Amps

16 2 Types of Electric Currents 11. AC - In alternating current, the charges continually shift from flowing in one direction to flowing in the reverse direction. 11. DC - In direct current, the charges always flow in the same direction. BrainPop Current Electricity

17 Voltage VOLTAGE is a measure of how much work is needed to move a charge between two points. How are Voltage and Electric Current related? What is Current? Higher voltage = High amps (current) High Voltage to Low Voltage How would you expect the voltage to change from the generator to our homes?

18 Transformers A transformer increases or decreases the voltage of alternating current.

19 Resistance Resistance is another factor that determines the amount of current in a wire. RESISTANCE is the opposition to the flow of electric charge. Thinner Wire = Higher Resistance Longer Wire = Higher Resistance

20 Resistance and Materials Good conductors, such as copper, have low resistance. Poor conductors, such as iron, have higher resistance. Is an insulator a good conductor or a poor conductor? Poor conductor high resistance Is a wire a good conductor or a poor conductor? Good conductor low resistance

21 Electric Power The rate at which electrical energy is changed into other forms of energy is electric power. The unit for power is the watt (W), and the symbol for power is the letter P.

22 Electric Circuits 13. A roller-coaster car follows a fixed pathway. The ride s starting point and ending point are the same place. This kind of closed pathway is called a CIRCUIT.

23 3 Parts of an Electric Circuit

24 15. A SWITCH Controls The Circuit What direction do you think the electricity flows from the battery? positive to negative

25 2 Types of Circuits A SERIES CIRCUIT has all parts connected in a single loop. There is only ONE path for charges to follow, so the charges moving through a series circuit must flow through each part of the circuit. A PARALLEL CIRCUIT is a circuit in which loads are connected side by side. Charges in a parallel circuit have MORE than one path on which they can travel. Practice Page

26 Advantages and Disadvantages of Series Circuits Disadvantages: It is impossible to control the bulbs individually. If one bulb is on they are all on If a bulb or the pathway were broken in any way, the other bulbs would go out. The more output devices you add the slower the current becomes. Advantages : You can add more power sources, like batteries, and increase the force of the output which grants you more power.

27 Advantages and Disadvantages of Parallel Circuits Advantages : If one bulb broke the others would continue going. The brightness of the bulbs would be greater than the brightness of bulbs in series. Increasing the number of output devices does not increase the resistance like it does in series. Disadvantages: There could be a risk of fire in some cases. With multiple power sources, the total power stays at the same voltage as that of the single power source.

28 Electricity and Magnetism S8P5. Students will recognize the characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. b. Demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy. c. Investigate and explain that electric currents and magnets can exert force on each other.

29 Magnets and Magnetism More than 2,000 years ago, the Greeks discovered a mineral that attracted things made of iron. Because this mineral was found in a part of Turkey called Magnesia, the Greeks called it magnetite. What is a Magnet? Any material that attracts iron or things made of iron. All magnets have two poles a north pole and a south pole Magnets exert forces on each other and are surrounded by a magnetic field.

30 Magnetic Poles MAGNETIC POLES are points on a magnet that have opposite magnetic qualities.

31 North Pole and South Pole Magnetic poles are always in pairs. You will never find a magnet that has only a north pole or only a south pole.

32 Magnetic Force When you bring two magnets close together, the magnets each exert a magnetic force on the other.

33 Magnetic Fields A magnetic field exists in the region around a magnet in which magnetic forces can act. The shape of a magnetic field can be shown with lines drawn from the north pole of a magnet to the south pole. These lines map out the magnetic field and are called magnetic field lines. The closer together the field lines are, the stronger the magnetic field is. The lines around a magnet are closest together at the poles, where the magnetic force on an object is strongest.

34 Materials Matter The Cause of Magnetism Some materials are magnetic. Some are not. This is a physical property of matter. Just like in the law of electric charges, opposite poles attract and alike poles repel in magnetism.

35 Non Magnetic Materials Electrons in all atoms are surrounded by a Magnetic Field and they each have a north and a south pole. In most materials, such as copper and aluminum, the magnetic fields of the individual atoms cancel each other out. Therefore, these materials are not magnetic.

36 Magnetic Materials When the north and south poles line up in a group of atoms, then a domain is formed. The arrangement of the domains in an object determines whether a material is magnetic or not.

37 Types of Magnets There are two types of magnets: ferromagnets andelectromagnet.

38 Types of Magnets Ferromagnets Made of iron, nickle cobalt, or mixtures of those metals which naturally have a strong magnetic properties

39 Types of Magnets Electromagnet Made by an Electric Current. An electro magnet usually has an iron core.

40 Earth is a Magnet

41 Electromagnetism Electromagnetism is the interaction of electric currents or fields and magnetic fields

42 Solenoids A solenoid is a coil of wire that produces a magnetic field when carrying an electric current. The strength of the magnetic field of a solenoid increases as more loops are used. The magnetic field also becomes stronger as the current in the wire is increased.

43 Electromagnets An electromagnet is made up of a solenoid wrapped around an iron core.

44 Turning Electromagnets On and Off Electromagnets can be turned on or off as needed. A Magnetic Levitating Train (Mag-lev Train) is a good example of how we can use an electromagnet for transportation -Check out hoverboards

45 Magnets Can Make Electric Currents Not only can electric current turn a magnet on, but magnets can also create an electric current by moving inside a coil of wire, or when a wire moves between the poles of a magnet.

46 In a Nutshell Magnets affect electric currents and electric currents affect magnets.