Fundamentals of Electricity

• Electricity

  • Definition: A fundamental form of energy observable in positive and negative forms.

  • It includes both naturally occurring interactions (like lightning) and produced forms (like in generators).

  • Related Concepts:

  • Electric Current: The flow of electric charge, typically measured in amperes (A).

• Electrons

  • Definition: A stable subatomic particle with a negative charge found in all atoms, serving as the primary carriers of electricity in solids.

  • Properties:

  • Charge: q = -1.6021765 imes 10^{-19} coulombs.

  • Mass: 9.10938291 imes 10^{-31} kilograms.

Electric Charge and Current

• Electric Charge (q)

  • Defined as a fundamental property of subatomic particles (like electrons and protons).

  • Measured in coulombs (C):

  • Magnitude of charge for one electron: q_{electron} = 1.602 imes 10^{-19} ext{ C}.

  • Charge of one mole of electrons (Faraday's Constant, F):
    F = 9.649 imes 10^{4} ext{ C/mol}, calculated as F = (1.602 imes 10^{-19} ext{ C}) imes (6.022 imes 10^{23} ext{ mol}^{-1}).

• Electric Current (I)

  • Definition: Movement or flow of charged particles.

  • Measured in amperes (A):

  • I = rac{C}{s}, i.e., coulombs per second.

  • Related to Faraday's Constant for electron flow in moles per second.

Electrical Work

• Electrical Work

  • Definition: Difference in electric potential between two points indicating work done by moving electrons.

  • Measured in joules (J).

  • Potential difference (E): Measured in volts (V) as V = rac{J}{C}, where

  • ext{Work} = E imes q.

Electrochemical Reactions

• REDOX Reactions

  • Definition: Chemical reactions where electrons transfer between substances.

  • Characteristics:

  • Oxidation: Loss of electrons by a substance (electron donor).

  • Reduction: Gain of electrons by a substance (electron acceptor).

Electrochemical Cells

• Types of Electrochemical Cells

  • Galvanic Cell: Converts chemical energy into electrical energy, generating a spontaneous reaction.

  • Electrolytic Cell: Requires an external potential difference to drive a non-spontaneous reaction.

• Components: Two electrodes connected by an electrolyte.

  • Anode: Electrode where oxidation occurs (positive charge).

  • Cathode: Electrode where reduction occurs (negative charge).

Measurement Techniques

• Potentiometry

  • Measurement of electrical potential difference without current flow, allows ion concentration assessment.

• Amperometry

  • Measurement of current at a fixed voltage, proportional to analyte concentration.

• Voltammetry

  • Measures current while varying the potential, often used for dynamic behavior of substances.

Nernst Equation

• Used to determine cell electromotive force (E): E = E^{0} - \frac{RT}{nF} \ln(Q)

  • Where:

    • E^{0} = standard reduction potential.

    • R = molar gas constant.

    • T = temperature in Kelvin.

    • n = number of moles of electrons transferred.

    • F = Faraday’s constant, 96485 ext{ C/mol}.

    • Q = reaction quotient.

Electrochemical Analytical Methods

• Methods:

  • Potentiometry, Coulometry, Amperometry, Voltammetry analyzed to determine concentrations of various analytes (e.g., electrolytes, blood gases, vitamins).

Practical Applications in Clinical Chemistry

• Point-of-Care Devices

  • Utilization of electrochemical principles to develop rapid devices for detecting elements like glucose, responsible for measuring analyte concentrations efficiently.

• Methods such as Ion-Selective Electrodes and pH Meters are crucial in clinical laboratory settings for precise measurements.

Key Terminology

• Electrolyte: Conductive solutions formed by the dissociation of ions.

• Electrode: Conducts electrons into/out of the chemical species involved.

• Reference Electrode: Maintains a constant potential.

• Indicator Electrode: Changes potential in response to analyte concentration changes.

• Common Applications: Monitoring, evaluating enzyme activity, or electrolyte analysis in biological contexts.