Storage & Transmission of Electrical Energy

Static Electricity

  • Some particles in the atom are electrically charged.
  • Most objects have equal amounts of protons and electrons, resulting in a neutral charge.
  • Neutral objects exhibit static electricity.

Charged Objects

  • To become positively charged, an object must lose electrons.
  • To become negatively charged, an object must gain electrons.

Static Charge

  • When an object loses or gains electrons, it builds up a static charge.
  • Static means stationary or not moving.

Interaction of Electrically Charged Objects

  • There are forces between charged particles.
  • Like charges repel each other.
  • Opposite charges attract each other.
  • When charged objects are brought near neutral objects, they cause charge separation in the neutral object.

Electrical Discharge (Static Shock)

  • Electrical discharge is the buildup of a negative charge that jumps to another object, attracted to a positive charge.
  • Example: Walking across a carpet and 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 door knob (+).

Van de Graaff Generators

  • A Van de Graaff generator is a device that produces a buildup of static electricity using friction.
  • A rubber belt rubs on a metal sphere.
  • Electrons are transferred from the rubber to the metal.
  • Electrons transfer to you when you touch the generator.

Cells and Batteries

Electrochemical Cells

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

Components of an Electrochemical Cell

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

How Electrochemical Cells Work

  • Electrons travel from the negative (-) electrode to the positive (+) electrode.
  • One electrode loses electrons and becomes positive (+), which is the cathode.
  • The other electrode gains electrons and becomes negative (-), which is the anode.
  • This results in a 'potential difference,' or voltage.
  • Voltage represents the pressure between electrons.
  • It can be measured with a voltmeter.
  • The unit of measurement is volts (V).

Optimal Conditions for Electrochemical Cells

  • Work best with:
    • Two different metal electrodes.
    • Strong, concentrated electrolyte.
    • Increased surface area of electrodes exposed to electrolyte.
  • Will not work with:
    • Electrodes of the same metal.
    • Molecular electrolyte.

Types of Electrochemical Cells

Primary Cells
  • Chemical reactions that cannot be reversed.
  • Examples: Dry cells and wet cells.
Dry Cell
  • Electrolyte is a paste.
  • Safe and portable.
  • Only leaks if the negative electrode is degraded.
Wet Cell
  • Has two metal electrodes and an electrolyte solution (acid).
  • Can spill if tipped.
  • Corrosive electrolyte can leak.
  • Example: Lead-acid car battery.
Secondary Cells
  • Rechargeable cells.
  • Chemical reaction can be reversed.
  • Electricity restores the reactants.

Battery

  • Multiple cells connected together.
  • Most are sealed into cases with only two terminals.
  • Produces more voltage, equaling more power.

Electrochemistry

  • Electricity and chemical reactions.
  • Some reactions use electrons.
  • Other reactions create free electrons.

Electrolysis

  • Uses electricity to split a compound into its 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

  • Uses electricity to coat an object with a thin layer of metal.
  • The flow of electrons deposits atoms of positively (+) charged metal onto a negatively (–) charged object.
  • Protects from corrosion.

Anodizing

  • Coats aluminum objects with aluminum oxide.
  • Makes the object harder.

Electrorefining

  • Uses electricity to purify a substance.
  • Example: Copper sulfate →\rightarrow pure copper.