Storage & Transmission of Electrical Energy Notes

2.1 STATIC ELECTRICITY

  • Some particles within an atom possess electrical charge.
  • Most objects maintain an equilibrium with equal numbers of protons and electrons, resulting in a neutral charge.
  • Neutral STATIC ELECTRICITY is the state where an object exhibits no net electrical charge.

Charging Objects

  • An object becomes positively charged through the loss of electrons.
  • Conversely, an object becomes negatively charged by gaining electrons.

Static Charge Buildup

  • When an object experiences a loss or gain of electrons, it accumulates static charge.
  • The term "static" implies that the charge is stationary and not in motion.

Interactions Between Electrically Charged Objects

  • Like charges repel each other, while opposite charges attract.
  • When charged objects are brought near neutral objects, they induce charge separation within the neutral object.

Electrical Discharge (Static Shock)

  • Electrical discharge is the buildup of negative charge that jumps to another object and is attracted to a positive charge.
  • Example: Walking across a carpet & touching a door knob
    • Electrons are transferred from the carpet to you.
    • You become negatively charged compared to the door knob.
    • Electrons jump from you to the positively charged door knob, causing a static shock.

Van de Graaff Generators

  • A Van de Graaff generator is a device that produces a buildup of static charge using friction.
  • It operates by rubbing a rubber belt against a metal sphere.
  • This friction causes electrons to transfer from the rubber to the metal.
    • Electrons transfer to you when you touch VDG

2.2 CELLS AND BATTERIES

Electrochemical Cells

  • Electrochemical cells transform chemical energy into electrical energy.
  • Electro refers to electricity.
  • Chemical refers to chemistry.
  • An electrochemical cell is a package of chemicals designed to produce small amounts of electricity from chemical reactions.
  • The reaction within the cell generates a flow of electrons between two substances.

Components of an Electrochemical Cell

  • Electrodes:
    • Two differing metals through which electric current enters or leaves.
  • Electrolyte:
    • A paste or liquid that forms ions.
  • Conductor:
    • Allows electrons to move.

Functioning of Electrochemical Cells

  • Electrons travel from the negative (-) electrode to the positive (+) electrode.
  • One electrode loses electrons and becomes positively charged (cathode).
  • The other electrode gains electrons and becomes negatively charged (anode).
  • This electron transfer results in a potential difference, also known as voltage.
  • Voltage is the pressure between electrons and is measured with a voltmeter; the unit of measure is volts (V).

Optimal Conditions for Electrochemical Cells

  • Electrochemical cells operate most effectively with:
    • Two different metal electrodes.
    • A strong, concentrated electrolyte.
    • Increased surface area of electrodes exposed to the electrolyte.
  • An electrochemical cell will NOT function with:
    • Electrodes made of the same metal.
    • A molecular electrolyte.

Types of Electrochemical Cells

1. Primary Cells

  • Chemical reactions that cannot be reversed.
  • Examples: DURACELL, DRY CELLS and WET CELLS
Dry Cell:
  • The electrolyte is a paste.
  • Dry cells are safe and portable.
  • They typically only leak if the negative electrode degrades.
Wet Cell:
  • Wet cells contain two metal electrodes and an electrolyte solution, often an acid.
  • They are prone to spillage if tipped.
  • The corrosive electrolyte can leak.
  • An example is a lead-acid car battery.

2. Secondary Cells

  • Secondary cells are rechargeable, meaning their chemical reactions can be reversed.
  • Electricity applied to the cell restores the reactants.

Battery

  • A battery consists of multiple cells connected together.
  • Most batteries are sealed into cases with only two terminals.
  • Connecting cells produces more voltage, thus more power.

Electrochemistry

  • Electrochemistry involves the relationship between electricity and chemical reactions.
  • Some reactions consume electrons, while others create free electrons.

Electrolysis

  • Electrolysis uses electricity to split compounds into their constituent elements.
  • Example: H<em>2O(l)→H</em>2(g)+O2(g)H<em>2O (l) \rightarrow H</em>2 (g) + O_2 (g)

Electroplating

  • Electroplating utilizes electricity to coat an object with a thin layer of metal.
  • The flow of electrons causes positively charged metal ions to deposit onto a negatively charged object.
  • This process protects against corrosion.

Anodizing

  • Anodizing coats aluminum objects with a layer of aluminum oxide.
  • This makes the object harder.

Electrorefining

  • Electrorefining uses electricity to purify a substance.
  • Example: copper sulfate (CuSO4) \rightarrow pure copper (Cu)