Transcript Unit 12* Conduction in Liquids and Gases

Unit 12
Conduction in Liquids and
Gases
Unit 12
Conduction in Liquids and Gases
Objectives:
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Define positive and negative ions.
Discuss electrical conduction in gases.
Discuss electrical conduction in a liquid.
Discuss several of the ionization
processes.
Unit 12
Conduction in Liquids and Gases
Ions
• An ion is a charged atom.
• Positive ions have a deficiency of
electrons.
• Negative ions have extra electrons.
Unit 12
Conduction in Liquids and Gases
Conduction in Liquids
• An electrolyte is a solution that will conduct
electricity.
• An electrolytic solution may be created from
distilled water by adding salt.
• A wide range of electrolytes can be created
from acids, alkalies, and metallic salts.
Unit 12
Conduction in Liquids and Gases
Conduction in a liquid.
Unit 12
Conduction in Liquids and Gases
Electrolysis
• Electrolysis is the process of separating
elements electrically.
Unit 12
Conduction in Liquids and Gases
Electroplating
• Electroplating uses electricity to deposit
atoms of one type of metal onto a different
metallic surface.
• DC current is passed from a power source,
through an electrode immersed in an
electrolyte, to the object to be plated and
back to the power source.
Unit 12
Conduction in Liquids and Gases
Electroplating Factors
1. The electrolyte solution must contain ions of
the metal to be plated.
2. Metal ions are always positively charged.
3. The plated object must be connected to the
negative power terminal.
4. Direct current is used as the power source.
5. The positive electrode is the same metal as
the new coating of the plated object.
Unit 12
Conduction in Liquids and Gases
The electroplating process.
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Conduction in Liquids and Gases
Conduction in Gases
• Conduction in gases occurs when an arc is
established across a gap between two
electrodes.
• The initial voltage required to start the arc
is very high.
• A reduced amount of voltage is required to
sustain an arc.
Unit 12
Conduction in Liquids and Gases
Conduction in Gases
• Current flow across the gap is aided by an
ion trail caused by ionized gas.
• An arc welder is an example of a practical
application.
Unit 12
Conduction in Liquids and Gases
Ionization in Gases
• Ionization potential is the amount of
voltage, or potential, an electron must
possess to cause ionization.
• Conduction in a gas occurs as a result of
electron impact from molecule to molecule.
• The pressure of the ionized gas affects the
required ion potential for current flow.
Unit 12
Conduction in Liquids and Gases
Electron impact frees electrons from gas
molecules.
Unit 12
Conduction in Liquids and Gases
Please insert Figure 11-10
Electron impact under high gas pressure.
Unit 12
Conduction in Liquids and Gases
Electron impact under low gas pressure.
Unit 12
Conduction in Liquids and Gases
The cathode ray tube is another application for
conduction in gases.
Unit 12
Conduction in Liquids and Gases
Review:
1. An electrolyte is a solution that will conduct
electricity.
2. An electrolytic solution may be created from
distilled water by adding salt.
3. Solutions of acids, alkalies, and metallic salts are
referred to as electrolytes.
Unit 12
Conduction in Liquids and Gases
Review:
4. Electroplating is the process of depositing the
atoms of one type of metal onto another.
5. Electroplating uses electricity to deposit atoms
from one metal onto a different metallic surface.
6. DC current passes from a power source, through
an electrolyte, to the object to be plated, and back
to the power source.
Unit 12
Conduction in Liquids and Gases
Review:
7. Factors affecting electroplating of metals:
a. The electrolyte solution must contain ions of the
plating metal.
b. Metal ions are always positively charged.
c. The object to be plated must be connected to
the negative power terminal.
d. The power source is direct current.
e. The positive terminal and the coating must be
of the same metal.
Unit 12
Conduction in Liquids and Gases
Review:
8.
The term electrolysis refers to the process of
separating elements electrically.
9. Conduction through a gas depends on the
ionization of gas molecules.
10. The amount of voltage required to cause
ionization of a gas is called the ionization
potential.
Unit 12
Conduction in Liquids and Gases
Review:
12. Gas can be ionized more easily when it is at a
low pressure than when it is at a high pressure.
13. The ionization potential is different for different
gasses.
14. The most important factor in the ionization of a
gas is electron impact.