stopping voltage

Examples of stopping voltage in the following topics:

• The Photoelectric Effect

  • An increase in the intensity of the incident beam (keeping the frequency fixed) increases the magnitude of the photoelectric current, though the stopping voltage remains the same.

• 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.

• Steelmaking and Refining

  • Once the electrodes have reached the heavy melt at the base of the furnace and the arcs are shielded by the scrap, the voltage is increased and the electrodes raised slightly, increasing the power to the melt.
  • It functions as a thermal blanket, stopping excessive heat loss, and helping to reduce erosion of the refractory lining.

• 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.