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Electric Current Is A Scalar Quantity It Has Direction But It Follows Algebraic Addition Not Vector Addition

Electric current is a scalar quantity that flows from the negative to the positive terminal, with conventional direction being the opposite. Current density measures electric current per unit area and is a vector quantity, while drift velocity refers to the average speed of charged particles in a conductor. Key concepts include relaxation time, mobility, and the relationship between electric current intensity and drift velocity.

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MAHANDAR KUMAR
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23 views14 pages

Electric Current Is A Scalar Quantity It Has Direction But It Follows Algebraic Addition Not Vector Addition

Electric current is a scalar quantity that flows from the negative to the positive terminal, with conventional direction being the opposite. Current density measures electric current per unit area and is a vector quantity, while drift velocity refers to the average speed of charged particles in a conductor. Key concepts include relaxation time, mobility, and the relationship between electric current intensity and drift velocity.

Uploaded by

MAHANDAR KUMAR
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Electric Current is a scalar Quantity It has direction but It follows algebraic addition

not vector addition.


Direction of current
• Actual Direction of Current: The actual direction of current is from the negative
terminal (-ve) to the positive terminal (+ve) because electrons, which are
negatively charged, flow from the negative terminal to the positive terminal in a
circuit.
• Conventional Direction of Current: The conventional direction of current is from
the positive terminal (+ve) to the negative terminal (-ve). This convention was
established before the discovery of electrons and is still widely used in circuit
analysis and diagrams, even though it is opposite to the actual electron flow. We
always use this conventional direction in most electrical and electronic
applications.
• In the Bohr model of hydrogen atom, the electrons revolve around the nucleus in a
circular path of radius of 5x10-11 m at a frequency of 6.8x1015 revolution per
second. Calculate the equivalent current.
Find charge flowing in wire in 10 sec.
Current density
Current density is defined as the amount of electric current flowing per unit area of cross-section
in a conductor.
. Current density is also a vector quantity, indicating the direction of current flow within the
conducting material.

NOTE :-Output current is always equal to input current


• Current flows through a constricted conductor as shown in figure.
The radius and the current density to the left of constriction are 2 mm and
4.2x105Am-2 respectively.
(a) How much current flows through them constriction?
(b) If the current density is doubled as emerges from the right side of the
constriction, what is the radius r₂?
• Drift Velocity (Vd)
The average velocity attained by charged particles, (eg. electrons) in a material due to an electric
field.
The SI unit of drift velocity is m/s.
Relaxation Time (T)
Relaxation time : The time interval between two successive collisions of electrons
with the atoms in the conductor is known as relaxation time (τ).

It is represented by the letter tau (τ).


• Derivation of Drift velocity
Consider a conductor of length I and area of cross-section A. When potential difference V is
applied, current flows through the conductor under the influence Electric field (E).

u = thermal velocity
τ = Relaxation time
a = acceleration
v = final velocity
• Now drift velocity is average velocity of free e- drifting towards the
end of Conductor.
• Mobility
It is defined as the ratio of drift velocity per unit Electric field.

Note: It is independent of potential difference.


• Relation between Electric current Intensity and drift Velocity
Consider a conductor of length I and Area of cross-section A. Let n is the free electron density
then,
Total no of free e- in a conductor N

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