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CURRENT  ELECTRICITY - I
1. Electric Current
2. Conventional Current
3.   Drift Velocity of electrons and current
4.   Current Density
5. Ohm’s Law
6.   Resistance, Resistivity, Conductance & 
Conductivity
7.   Temperature dependence of resistance
8.   Colour Codes for Carbon Resistors
9. Series and Parallel combination of 
resistors
10. EMF and Potential Difference of a cell
11. Internal Resistance of a cell
12. Series and Parallel combination of cells
Page 2


CURRENT  ELECTRICITY - I
1. Electric Current
2. Conventional Current
3.   Drift Velocity of electrons and current
4.   Current Density
5. Ohm’s Law
6.   Resistance, Resistivity, Conductance & 
Conductivity
7.   Temperature dependence of resistance
8.   Colour Codes for Carbon Resistors
9. Series and Parallel combination of 
resistors
10. EMF and Potential Difference of a cell
11. Internal Resistance of a cell
12. Series and Parallel combination of cells
Electric Current:
The electric current is defined as the charge flowing through 
any section of the conductor in one second.
I = q / t            (if the rate of flow of charge is steady)
I = dq / dt        (if the rate of flow of charge varies with time)
Different types of current:
I
t
0
a
b
c
d)  Alternating current whose 
magnitude varies continuously 
and direction changes 
periodically
a) Steady current which does not 
vary with time 
b) & c) Varying current whose   
magnitude varies with time
d
Page 3


CURRENT  ELECTRICITY - I
1. Electric Current
2. Conventional Current
3.   Drift Velocity of electrons and current
4.   Current Density
5. Ohm’s Law
6.   Resistance, Resistivity, Conductance & 
Conductivity
7.   Temperature dependence of resistance
8.   Colour Codes for Carbon Resistors
9. Series and Parallel combination of 
resistors
10. EMF and Potential Difference of a cell
11. Internal Resistance of a cell
12. Series and Parallel combination of cells
Electric Current:
The electric current is defined as the charge flowing through 
any section of the conductor in one second.
I = q / t            (if the rate of flow of charge is steady)
I = dq / dt        (if the rate of flow of charge varies with time)
Different types of current:
I
t
0
a
b
c
d)  Alternating current whose 
magnitude varies continuously 
and direction changes 
periodically
a) Steady current which does not 
vary with time 
b) & c) Varying current whose   
magnitude varies with time
d
Conventional Current:
Conventional current is the current 
whose direction is along the direction of 
the motion of positive charge under the 
action of electric field.
+
+
+
+
-
-
-
-
+
+
+
+
-
-
-
-
I
Drift Velocity and Current:
Drift velocity is defined as the velocity 
with which the free electrons get drifted 
towards the  positive terminal under the 
effect of the applied electric field.
I
v
d
= - (eE / m) t
- - - v
d
E
l
A
I = neA  v
d
v
d
= a t
v
d  
- drift velocity, a – acceleration, t – relaxation time,  E – electric field,        
e – electronic charge, m – mass of electron, n – number density of electrons, 
l – length of the conductor and A – Area of cross-section
Current is directly proportional 
to drift velocity.
Conventional current due to motion of 
electrons is in the direction opposite to 
that of motion of electrons.
+ + +
I
-
- -
Page 4


CURRENT  ELECTRICITY - I
1. Electric Current
2. Conventional Current
3.   Drift Velocity of electrons and current
4.   Current Density
5. Ohm’s Law
6.   Resistance, Resistivity, Conductance & 
Conductivity
7.   Temperature dependence of resistance
8.   Colour Codes for Carbon Resistors
9. Series and Parallel combination of 
resistors
10. EMF and Potential Difference of a cell
11. Internal Resistance of a cell
12. Series and Parallel combination of cells
Electric Current:
The electric current is defined as the charge flowing through 
any section of the conductor in one second.
I = q / t            (if the rate of flow of charge is steady)
I = dq / dt        (if the rate of flow of charge varies with time)
Different types of current:
I
t
0
a
b
c
d)  Alternating current whose 
magnitude varies continuously 
and direction changes 
periodically
a) Steady current which does not 
vary with time 
b) & c) Varying current whose   
magnitude varies with time
d
Conventional Current:
Conventional current is the current 
whose direction is along the direction of 
the motion of positive charge under the 
action of electric field.
+
+
+
+
-
-
-
-
+
+
+
+
-
-
-
-
I
Drift Velocity and Current:
Drift velocity is defined as the velocity 
with which the free electrons get drifted 
towards the  positive terminal under the 
effect of the applied electric field.
I
v
d
= - (eE / m) t
- - - v
d
E
l
A
I = neA  v
d
v
d
= a t
v
d  
- drift velocity, a – acceleration, t – relaxation time,  E – electric field,        
e – electronic charge, m – mass of electron, n – number density of electrons, 
l – length of the conductor and A – Area of cross-section
Current is directly proportional 
to drift velocity.
Conventional current due to motion of 
electrons is in the direction opposite to 
that of motion of electrons.
+ + +
I
-
- -
Current density:
Current density at a point, within a conductor, is the current through a unit 
area of the conductor, around that point, provided the area is perpendicular 
to the direction of flow of current at that point.
J = I / A  = nev
d
In vector form, I = J . A
Ohm’s Law:
The electric current flowing through a conductor is directly 
proportional to the potential difference across the two ends of the 
conductor when physical conditions such as temperature, mechanical 
strain, etc. remain the same.
I
V
I a V or V a I or V = R I
V
I
0
Page 5


CURRENT  ELECTRICITY - I
1. Electric Current
2. Conventional Current
3.   Drift Velocity of electrons and current
4.   Current Density
5. Ohm’s Law
6.   Resistance, Resistivity, Conductance & 
Conductivity
7.   Temperature dependence of resistance
8.   Colour Codes for Carbon Resistors
9. Series and Parallel combination of 
resistors
10. EMF and Potential Difference of a cell
11. Internal Resistance of a cell
12. Series and Parallel combination of cells
Electric Current:
The electric current is defined as the charge flowing through 
any section of the conductor in one second.
I = q / t            (if the rate of flow of charge is steady)
I = dq / dt        (if the rate of flow of charge varies with time)
Different types of current:
I
t
0
a
b
c
d)  Alternating current whose 
magnitude varies continuously 
and direction changes 
periodically
a) Steady current which does not 
vary with time 
b) & c) Varying current whose   
magnitude varies with time
d
Conventional Current:
Conventional current is the current 
whose direction is along the direction of 
the motion of positive charge under the 
action of electric field.
+
+
+
+
-
-
-
-
+
+
+
+
-
-
-
-
I
Drift Velocity and Current:
Drift velocity is defined as the velocity 
with which the free electrons get drifted 
towards the  positive terminal under the 
effect of the applied electric field.
I
v
d
= - (eE / m) t
- - - v
d
E
l
A
I = neA  v
d
v
d
= a t
v
d  
- drift velocity, a – acceleration, t – relaxation time,  E – electric field,        
e – electronic charge, m – mass of electron, n – number density of electrons, 
l – length of the conductor and A – Area of cross-section
Current is directly proportional 
to drift velocity.
Conventional current due to motion of 
electrons is in the direction opposite to 
that of motion of electrons.
+ + +
I
-
- -
Current density:
Current density at a point, within a conductor, is the current through a unit 
area of the conductor, around that point, provided the area is perpendicular 
to the direction of flow of current at that point.
J = I / A  = nev
d
In vector form, I = J . A
Ohm’s Law:
The electric current flowing through a conductor is directly 
proportional to the potential difference across the two ends of the 
conductor when physical conditions such as temperature, mechanical 
strain, etc. remain the same.
I
V
I a V or V a I or V = R I
V
I
0
Resistance:
The resistance of conductor is the opposition offered by the 
conductor to the flow of electric current through it.
R = V / I
Resistance in terms of physical features of the conductor:
I = neA | v
d
|
I = neA (e  |E| / m) t
ne
2
At
m
V
l
I =
ne
2
At
V
I
=
ml
ne
2
t A
R  =
m    l
A
R  = ?
l
where ? = 
ne
2
t
m
is resistivity or 
specific resistance
Resistance is directly proportional to 
length and inversely proportional to 
cross-sectional area of the conductor 
and depends on nature of material.
Resistivity depends upon nature of 
material and not on the geometrical 
dimensions of the conductor.
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157 videos|453 docs|185 tests

FAQs on PPT: Current Electricity - 1 - Physics Class 12 - NEET

1. What is current electricity?
Ans. Current electricity refers to the flow of electric charge in a conductor. It is the movement of electrons through a closed circuit, usually powered by a source such as a battery or generator. Current electricity is responsible for powering various electrical devices and systems.
2. How is current electricity different from static electricity?
Ans. Current electricity and static electricity are two different phenomena. While current electricity involves the continuous flow of electric charge, static electricity refers to the buildup of electric charge on the surface of an object. Static electricity is usually caused by friction between two objects, while current electricity requires a closed circuit for the flow of electrons.
3. What are the units used to measure current electricity?
Ans. The unit used to measure current is the ampere (A). It represents the rate at which electric charge flows in a circuit. Additionally, other common units used to measure current include milliamperes (mA) and microamperes (μA), which represent smaller values of current.
4. How does current electricity affect resistors in a circuit?
Ans. In a circuit, resistors are components that impede the flow of current. When current passes through a resistor, it experiences resistance, causing a decrease in the current flow. The relationship between current, voltage, and resistance is governed by Ohm's Law, which states that the current flowing through a resistor is directly proportional to the voltage across it and inversely proportional to its resistance.
5. What is the role of conductors and insulators in current electricity?
Ans. Conductors and insulators play crucial roles in current electricity. Conductors, such as metals, have low resistance and allow the flow of electric current. They provide a path for electrons to move through. On the other hand, insulators have high resistance and restrict the flow of electric current. They are used to protect wires and prevent unintended current flow, ensuring safety in electrical systems.
157 videos|453 docs|185 tests
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