- Electric current is the rate of flow of charge.
- Battery provides the driving force required to move the charges along the wire from one terminal to another.
- The constant voltage difference between the two terminals of the wire maintains the constant electric current through the wire.
- Electric current is measured in terms of amperes where
**1 ampere = 1 coulomb / second** - Voltage is measured in terms of volt where

**1 volt = 1 joule /coulomb** - Resistance is a property that resists the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (O).
- Resistivity is defined as the resistance offered by a cube of the material of side 1 m when the current flows perpendicular to the opposite faces of the cube.
- Ohm's law: The potential difference across the ends of a resistor is directly proportional to the current through it, provided its temperature remains the same.
- The resistance of a conductor depends directly on its length, inversely on its area of cross – section, and also on the material of the conductor.
- In Series combination of resistors:
- he current flowing through each resistor is the same
- The potential difference across the ends of the series combination is distributed across the resistors
- The equivalent resistance is greater than the greatest resistance in the combination.
- In Parallel combination of resistors:
- The potential difference across each resistor is same and is equal to the potential difference across the combination.
- The main current divides itself and a different current flow through each resistor.
- The equivalent resistance is lesser than the least of all the resistances.
- The effect of heating current due to which heat is produced in a wire when current is passed through it is called heating effect of current.
- Electric power is the rate at which electrical energy is produced or consumed in an electric circuit.
- The unit of power is watt (W). One watt of power is consumed when 1 A of current flows at a potential difference of 1 V.
- The commercial unit of electric energy is kilowatt hour (kW h), commonly known a 'unit'.

- The current I through the cross – section of a conductor is Where Q is net charge flowing across the cross – section of a conductor in time t.
- Potential difference (V) between two points = work done (W)/ Charge (Q)

**V = W/ Q** **Ohm's law: V = I R**- The equivalent resistance in series circuit is the sum of the individual resistances -

**R = R1 + R2 + R3** - The equivalent resistance of a parallel circuit containing resistances R1, R2, R3 is given as

**1/RP = 1/R1 +1/R2 + 1/R3** - The electric power P is given by P = VI

**Or P = I2R = V2/ R** - The electrical energy dissipated in a resistor is given by
- Joule's law of heating;
**H = I2Rt** **1 kW h = 3, 600, 000 J = 3.6 x 106 J**