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Electricity and Magnetism

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Electricity and Magnetism IPC Spring 2008 Electricity and Magnetism 1. A magnet is any substance that can attract iron and other magnetic materials. – PowerPoint PPT presentation

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Title: Electricity and Magnetism


1
Electricity and Magnetism
  • IPC Spring 2008

2
Electricity and Magnetism
  • 1. A magnet is any substance that can attract
    iron and other magnetic materials.
  • Examples of magnetic materials are cobalt,
    nickel, iron, and alloys of these metals.

3
Electricity and Magnetism
  • Properties of Magnets
  • a). Ends of a magnet north pole and south pole

  • b). Characteristics of a magnet like poles
    repel, unlike poles attract.
  • c). Ways of making a magnet
  • 1. Contact (stroking in one direction),
  • 2. Electricity (contact with flowing electrons)
  • 3. Induction (not touching another object, but
    lying in its magnetic field)
  • d). Ways to demagnetize a magnet
  • 1. Heating,
  • 2. Jarring
  • 3. Rub back and forth with another magnet.

4
Electricity and Magnetism
  • 2. The needle of a compass is a magnet.
  • The north pole of the needle is attracted to the
    south magnetic pole of the earth.
  • The geographic north pole of the earth is a
    magnetic south pole.

5
Electricity and Magnetism
  • 3. The area around the magnet where the magnetic
    force acts is called the magnetic field.
  • A circular magnetic field is produced around a
    wire that is carrying a current. If the wire is
    made into a coil, the ends of the coil become
    magnetic poles.
  • When a wire is moved perpendicularly through a
    magnetic field or when a magnetic field is moved
    perpendicularly to a wire, a current is produced
    in the wire.

6
Electricity and Magnetism
  • 4.    An electromagnet is a current-carrying coil
    of wire around an iron core.
  • The magnetic field of the coil and the magnetic
    field of the iron core combine to produce a
    stronger magnetic field.
  • The strength of an electromagnet can be increased
    by increasing the current or increasing the
    number of turns in the coil of wire.
  • Examples of electromagnets are generators,
    transformers, and electric motors.

7
Electricity and Magnetism
  • 5. Electricity is a form of energy that deals
    with the movement of electrons.
  • The three forms of electricity are
  • a. static electricity - the net accumulation of
    electric charges on an object,
  • b. current electricity - the flow of electrons
    in a circuit
  • c. magnetism - the attraction and repulsion
    between magnetic poles

8
Electricity and Magnetism
  • 6. Atoms contain electrically charged particles
    called protons and electrons.
  • Protons have a positive charged.
  • Electrons have a negative charge.
  • Their charges are equal and opposite.

9
Electricity and Magnetism
  • 7.Two different uncharged objects can become
    electrically charged when they are rubbed against
    each other.
  • Electrons can be lost by one object and gained by
    the other.
  • Each object no longer has equal numbers of
    protons and electrons.
  • NOTE only the electron (-) moves.

10
Electricity and Magnetism
  •  8. An object that has more electrons than
    protons is said to be negatively charged.
  • An object that has fewer electrons than protons
    is said to be positively charged.
  • If the positive charges equal the negative
    charges, there is no net charge on the object
    (neutral charge).
  •  

11
Electricity and Magnetism
  • 9. Objects with like charges repel and objects
    with unlike charges attract.
  • 10. A conductor is a substance that allows an
    electric charge to flow through it easily.
  • An insulator does not allow the easy flow of
    electric charge through it. 

12
Electricity and Magnetism
  • 11.A simple electric circuit is made up of a
    voltage source, a conductor and a load.
  •  
  • 12.Direct current is defined as flowing from the
    negative terminal to the positive terminal.
  • Alternating current is the type of current that
    changes direction at regular intervals in a
    circuit. AC is produced by generators. In this
    country it switches 60 times per second.

13
Electricity and Magnetism
  • 13.An electric circuit in which the current flows
    in a complete path is called a closed circuit.
  • An electric circuit that is broken somewhere
    along the current's path is called an open
    circuit.

14
Electricity and Magnetism
  • 14.A system through which an electric current can
    travel is called an electric circuit.
  • Electric current is the flow of electrons.
  • Electric current is measured in units called
    amperes, or amps (a).
  • Potential difference, or voltage, is a measure of
    the energy available to move charges in a
    circuit. Potential difference is measured in
    volts (V).

15
Electricity and Magnetism
  • The common American household voltage is 110 V.
  • The opposition to the flow of charges in a
    substance is called resistance.
  • Resistance is measured in units called ohms (O).

16
Electricity and Magnetism
  • 15. A schematic diagram is a drawing of an
    electrical circuit using symbols.
  • Schematic diagrams can be used to represent
    series and parallel circuits.
  • Note In a battery symbol the whole line
    represents 1 volt. The half line represents a
    half a volt. So, this represents 1.5
    volts. A cell is 1.5 volts as shown here.

17
Electricity and Magnetism
  •  16.A series circuit has only one path for the
    current.
  • A parallel circuit has more than one path for the
    current.
  • NOTE A parallel circuit offers less resistance
    than a series circuit because each electron does
    not have to travel through each resistance they
    take their own separate path.
  • In a series circuit, each electron must travel
    through the entire circuit.

18
Electricity and Magnetism
  • 17.A voltmeter is a device that measures the
    potential difference between two points in an
    electric circuit. It measures in volts. A
    voltmeter makes a branch when connected, in order
    to measure a drop in voltage before and after a
    resistor (or lamp) in a straight line with the
    source of voltage.

19
Electricity and Magnetism
  • An ammeter is a device that measures the current
    of an electric circuit. It measures in amperes.
    (amps) An ammeter is not on a branch by itself,
    but is always connected in a line with the source
    of voltage.

20
Electricity and Magnetism
  • 18.Fuses and circuit breakers are devices for
    interrupting the flow of charges in a circuit.
    They are both safety devices that open an
    electric circuit.
  • Fuses must be replaced and circuit breakers may
    be reset.

21
Electricity and Magnetism
  • 19. The relationship of resistance, voltage and
    current can be written as a formula, called Ohm's
    law.
  • VIR or IV/R
  • R stands for resistance and is measured in ohms
    (?).
  • V stands for voltage and is measured in volts.
  • I stands for current and is measured in amps.

22
Electricity and Magnetism
  • 20. The relationship between electric power and
    current is shown by the following formula
  • P VI
  • In this formula, P stands for power and is
    measured in watts. V stands for voltage (volts)
    and I stands for current (amps).

23
Electricity and Magnetism
  • 21. Much of the electricity we use daily is
    obtained using fossil fuels, such as coal,
    petroleum and natural gas. These sources of
    energy are being depleted and alternative energy
    sources are being developed to produce
    electricity with greater efficiency. Alternative
    energy sources include

24
Electricity and Magnetism
  • a. solar - accessing energy in sunlight through
    the use of solar panels.
  • b. tidal the inward flow of water is trapped
    and the kinetic energy of the water escaping out
    is used to generate current.

25
Electricity and Magnetism
  • c. geothermal using the consistent temperature
    of the earth to keep homes warm or cool, or using
    molten rock rising near the surface of the
    earth's crust to superheat water and turn
    turbines in generators that generate electricity.

26
Electricity and Magnetism
  • d. nuclear energy released when atom nuclei are
    split or fused
  • nuclear fission The splitting of an atom's
    nucleus into two nuclei. Releasing heat that is
    used to generate steam and then, electricity.
  • Nuclear fusion is not being performed to generate
    electricity. In order to force two smaller
    nuclei into one larger nucleus, tremendous
    temperatures are required.

27
Electricity and Magnetism
  • e. wind the motion of air turning windmills and
    generators to generate electricity.
  • f. hydroelectricity available to communities
    near major rivers, the motion of flowing water
    flowing through a dam, turns generators that
    produce electricity.

28
Electricity and Magnetism
  • 22. Common sources for electrical devices
  • a). disposable batteries
  • b). rechargeable batteries
  • c). solar cells
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