1. Basics of Electric Current
• Electric Current (I):
o The flow of electric charge (electrons) through a
conductor.
o Formula: I=QtI = \frac{Q}{t}, where:
II = Current (in Amperes), QQ = Charge (in Coulombs), tt =
Time (in seconds).
• Unit of Current: Ampere (A)
o 1 Ampere = 1 Coulomb/1 second.
• Direction of Current:
o Conventional Current: Flows from positive to negative
terminal.
o Electron Flow: Opposite to conventional current
(negative to positive terminal).
2. Electric Potential and Potential Difference
• Electric Potential (V):
o The work done in bringing a unit positive charge from
infinity to a point in an electric field.
o SI Unit: Volt (V).
• Potential Difference:
o The work done in moving a unit charge between two
points in a circuit.
o Formula: V=WQV = \frac{W}{Q} Where: VV = Potential
difference, WW = Work done (Joules), QQ = Charge
(Coulombs).
, • 1 Volt:
o 1 Volt = 1 Joule/1 Coulomb.
3. Ohm's Law
• States that the current flowing through a conductor is directly
proportional to the potential difference across its ends,
provided the temperature and physical conditions remain
constant.
o Formula: V=IRV = IR Where: VV = Potential difference
(Volts), II = Current (Amperes), RR = Resistance (Ohms).
4. Resistance
• Definition:
o The opposition offered by a conductor to the flow of
electric current.
• Formula:
R=VIR = \frac{V}{I}
• SI Unit: Ohm (Ω\Omega)
o 1 Ohm = 1 Volt/1 Ampere.
• Factors Affecting Resistance:
1. Length of Conductor (LL):
R∝LR \propto L.
2. Area of Cross-Section (AA):
R∝1AR \propto \frac{1}{A}.
3. Material of Conductor:
Depends on the resistivity (ρ\rho) of the material.
4. Temperature:
Resistance increases with an increase in temperature (for metals).