Electric potential is the work done in carrying a unit positive charge from infinity to a point.
If W is the work done q is the charge then electric potential V = W/q.
The SI unit of electric potential is Volts(V).
Electric Potential Difference
The electric potential difference between two points is the work done in carrying a unit positive charge from
one point to the other.
The electric potential difference between points A and B
VAB = Work done to carry charge q from A to B / charge q
The SI unit of electric potential difference is Volts(V)
Electric Potential energy
Electric potential energy is the work which has to be done to bring charges to their respective locations against
the electric field with the help of a source of energy.
This work done is stored in the form of potential energy of the charges.
Ohm’s Law
Under similar physical conditions, the current flowing through a wire is directly proportional to the difference
in potential applied across its ends.
I $\propto$ V
V = I × R, where R is the resistance offered.
Resistance
Resistance is the opposition to the flow of current.
The SI unit of resistance is OHM ( Ω )
1 ohm is the resistance offered by a wire carrying 1 A current when 1 V is applied across its ends.
Factors Affecting Resistance
The resistance of a conducting wire depends on:
Nature of the material of the wire( Resistivity- ρ)
Length of the wire(l)
Cross-sectional area of the wire (A)
R = ρ (l/A)
Resistivity
The resistance offered by a wire of unit length and unit cross-sectional area is called resistivity.
The SI unit of resistivity is ohm-meter(Ω -m).
Resistivity is also referred to as specific resistance.
Reciprocal of resistivity is called conductivity.
Conductivity, σ = 1/ρ.
SI unit of conductivity is ohm-1 m -1 or mho-m-1
Effect of Temperature
The resistivity of a conductor increases linearly with increase in temperature.
The resistivity of an insulator increases with increase in temperature.
The resistivity of a semiconductor decreases with increase in temperature.
Resistivity of an alloy increases with increase in temperature.