Electronics

REVIEWING THE MAIN IDEAS

• electricity is the movement of electrons from one atom to another

• The study of electronics has allowed inventors to make many electrical devices, such as motion detectors and MP3 players.

• A(n) diode allows current to flow in only one direction.

• The ohm is the unit of measure for resistance

• At a hydroelectric plant, the generator changes the mechanical energy of the water into electrical energy.

• Electrons can flow only in a closed circuit.

• The unit of measure for voltage, or electromotive force, is the volt, and the symbols are V and E.

• Although very small, a(n) transistor controls current and amplifies voltage or current.

• A(n) integrated circuit, also called a chip, is tiny but may contain thousands of circuits.

• Sarah felt a shock of static electricity when she touched the metal filing cabinet.

•  Ohm's law describes how current is related to voltage and resistance.

• The unit of measure for current is the ampere, and the symbol is A.

• Current flowing in only one direction is direct current.

• A(n) electromagnet is created by wrapping wire around an iron core and then passing electric current through the wire.
  
  

STUDY GUIDE

• List the basic parts of an atom. When is an atom neutral?

  • An atom has a nucleus surrounded by a cloud of electrons.

    The nucleus of most atoms includes protons and neutrons. An atom is neutral when the number of protons equals the number of electrons.

• ionization

  • The process by which an atom gains or loses electrons.

• If an electron is lost, the atom becomes a positive ion because it has more protons than electrons.

• What keeps electrons bound to an atom

  • The positive charges of protons in the nucleus attract the negatively charged

    electrons in each of the shells. This attraction helps keep the electrons from flying away from the nucleus.

• What is voltage? What is another name for voltage?

  • Voltage is the electric pressure that causes current to flow. It is the force that

    sets charges in motion. Another name for it is electromotive force (emf).

• Name four good conductors of electricity.

  • Four examples are copper, aluminum, silver, and gold.

• current

  • The flow of electrons in a wire or other conductor.

• Why do plastics and ceramics make good insulators?

  • These materials are made of atoms that have a tight hold on electrons and very few free electrons. Thus they resist the flow of voltage.

• What is the name for a material that has high resistance? What type has low resistance?

  • Insulators have very high resistance. Conductors have low resistance.

• What is Ohm’s law?

  • Ohm’s law states that current (I) is equal to the voltage (E) divided by the resistance (R).

• What are the conductors and conducting solution in a battery cell called?

  • The conductors are electrodes. The solution is electrolyte.

• Describe a simple generator. How does it produce voltage?

  • A simple generator consists of a coil of wire wrapped around a metal core

    and placed between the poles of a magnet. As the armature (wire and core

    assembly) rotates, the coil cuts across the magnetic field. As a result, voltage is induced in the coil.

• What are electromagnets?

  • Electromagnets are powerful magnets created by wrapping wire around an iron core and then passing electric current through the wire.

• Name the three components of a simple circuit. Which is the component that uses

  the electric energy?

  • Power source, conductor, and load. The load is the component that uses the

    electric energy.

• In which type of circuit is voltage the same in all branches? In which circuit is cur-

  rent the same at all points?

  • Parallel circuit; series circuit.

• Define electronics.

  • The study of the control of electron flow in a circuit.

• What does a transistor do in a circuit?

  • It acts as an electronic switch.

• What is a semiconductor able to do that other materials cannot?

  • A semiconductor is a material that can change from conductor to insulator as conditions change.

• An electronic device that can reduce the current flow in a circuit

  is a(n) _____. A device that can store electrical charges is a(n) ____.

  • resistor; capacitor

• The original devices that were used as electronic switches were called tubes. Tubes

  were about the size of a salt shaker. If tubes had never been replaced by transistors,

  what would be different about modern electronic devices?

  • that since tubes are large and transistors

    are tiny, electronic devices that use tubes would be much larger than the ones we have today, which use transistors.

WAR OF CURRENTS

• What was the “War of Currents” about?

  • In the late 1800s, Edison and his company, General Electric, had a monopoly on power distribution. GE distributed direct current. Nikola Tesla developed a power distribution system using alternating current. Tesla and the Westing- house company competed with Edison and General Electric to become the major power suppliers to consumers.

• Which type of current, AC or DC, were Tesla and Edison each promoting as the better choice?

  • Tesla promoted AC. Edison promoted DC.

• List at least four patents each that Tesla and Edison were granted.

  • Tesla received more than 100 patents in his lifetime. Edison

    was granted more than 1,000.

• What were the advantages of DC power? What were the disadvantages?

  • Advantages: Direct current worked well for certain applications, such as incandescent lamps and electroplating.

  • Disadvantages: At the time (late 1800s), direct current could not be easily sent over long distances due to excessive voltage drops after one mile. Direct current also could not be easily changed to a higher or lower voltage. The voltage supplied had to be correct for the device that received it. This meant separate lines were needed for different appliances.

• What were the advantages of AC power? What were the disadvantages?

  • Advantages: Alternating current could be transmitted over long distances with less voltage drop. The current and voltage could be easily changed by transformers.

  • Disadvantages: Low-frequency alternating current is actually more dangerous to living organisms than a similar level of direct current. The AC can cause hearts to beat out of rhythm, leading to ventricular fibrillation and death.

• Which type of power—AC or DC—is now transmitted into homes in the United States?

  • Alternating current

• What controversial event did Edison create using an elephant? What was he trying to demonstrate?

  • He electrocuted Topsy the Elephant to demonstrate that AC was more dangerous than DC.

• What do many historians believe that Tesla rather than Guglielmo Marconi should be credited for?

  • the radio