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Question
Which of the following characteristics of electrons determines the current in a conductor?
Options
Drift velocity alone
Thermal velocity alone
Both drift velocity and thermal velocity
Neither drift nor thermal velocity
Solution
Drift velocity alone
Explanation:
Drift velocity is the average uniform velocity acquired by free electrons inside a metal by the application of an electric field which is responsible for the current through it
The direction of drift velocity for electron in a metal is opposite to that of applied electric field (i.e. current density `vecJ`).
`V_d oo E`, i.e. greater the electric field, larger will be the drift velocity.
The relationship between current and drift speed is given by I = ne Avd
Here, l is the current and vd is this drift velocity.
So, `I oo v_d`
Thus, only drift velocity determines the current in a conductor.
Important point: Remember direction of drift velocity and current is opposite, so we are taking the magnitude of drift velocity or drift speed of free electrons.
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