voltage

Examples of voltage in the following topics:

• Mercury Battery

  • Mercury batteries have the advantages of a long shelf life of up to 10 years and steady voltage output.
  • Sodium hydroxide cells have nearly constant voltage at low discharge currents, making them ideal for hearing aids, calculators, and electronic watches.
  • Potassium hydroxide cells, in turn, provide constant voltage at higher currents, making them suitable for applications requiring current surges, such as photographic cameras with flash and watches with a backlight.

• Concentration of Cells

  • The Nernst equation can be used to calculate the output voltage changes in a pair of half-cells under non-standard conditions.
  • When a change in the concentration or activity of reactants occurs, or the temperature or pressure changes, the output voltage changes.

• Conductors

  • According to band theory, a conductor is simply a material that has its valence band and conduction band overlapping, allowing electrons to flow through the material with minimal applied voltage.
  • In most materials, the direct current is proportional to the voltage (as determined by Ohm's law), provided the temperature remains constant and the material remains in the same shape and state.
  • On the left, a conductor (described as a metal here) has its empty bands and filled bands overlapping, allowing excited electrons to flow through the empty band with little push (voltage).
  • Semiconductors and insulators have a greater and greater energetic difference between the valence band and the conduction bands, requiring a larger applied voltage in order for electrons to flow.

• Cathode Rays

  • If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass opposite the negative electrode is observed to glow from electrons emitted from the cathode.
  • The voltage applied between the electrodes accelerates these low mass particles to high velocities.
  • With no obstructions, these low mass particles were accelerated to high velocities by the voltage between the electrodes.
  • Connect the two electrodes to a high voltage source and see them produce cathode rays.

• Millikan's Oil Drop Experiment

  • The droplets entered the space between the plates and, because they were charged, they could be controlled by changing the voltage across the plates.
  • A likely looking drop was selected and kept in the middle of the field of view by alternately switching off the voltage until all the other drops fell.
  • The droplets enter the space between the plates and can be controlled by changing the voltage across the plates.

• Electrolytic Properties

  • When electrodes are placed in an electrolyte solution and a voltage is applied, the electrolyte will conduct electricity.
  • When electrodes are placed in an electrolyte solution and a voltage is applied, the electrolyte will conduct electricity.

• The Nernst Equation

  • It can also be used to determine the total voltage, or electromotive force, for a full electrochemical cell.

• Equilibrium Constant and Cell Potential

  • It can also be used to determine the total voltage, or electromotive force, for a full electrochemical cell.
  • In other words, a voltage could be applied to stop the movement of the K+ ions.

• Other Rechargeable Batteries

  • They are fragile and thus need a protective circuit to limit peak voltages.
  • They are often available in series "packs" to increase the total available voltage.

• Mass Spectrometry to Measure Mass

  • Here, ions are passed through four parallel rods, which apply a varying electric voltage.
  • Depending on the applied voltage, only ions of a certain mass-to-charge ratio will pass through the analyzer.