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The flow of charged particles in a definite direction is called
electric current. Those substances which permit the flow of
charges through them are called conductors e.g. metals. However,
those substances which do not permit the flow through a conductor
if p.d. is maintained across its ends. |
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(I)
Current Carrier in Solid Conductors : In solid conductors
(e.g. metals), there are a large number of free electrons.
when electric field (i.e. pd) is applied to the conductor,
the free electrons start drifting in a particular direction
to constitute that current will only flow through a conductor
if p.d. is maintained across its ends. |
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(II)
Current Carrier in Liquids : Some liquids are conductors
of electricity. A Conducting liquid is called an electrolyte
(e.g. solution of CuSO4).
The electrolytic solution provides positive ions (e.g. Cu++)
and negative ions (e.g. SO4--).When
external electric field (i.e. p.d.) is applied, the positive
ions move in one direction and negative ions in the opposite
direction to constitute electric current. Hence in conducting
liquids, ions (positive and negative) are the current carriers. |
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(II)
Current Carrier in Gases : Under ordinary conditions,
gases are insulators. However, when a gas under low pressure
is subjected to high electric field (i.e. high p.d.),
Ionisation
of in gases molecules take place, i.e. electrons and positive
ions are formed. Hence, current carriers in gases are free
electrons and positive ions. |
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