**Points to Remember**

- In
**metals**, the charge carriers constituting current are free electrons. - In
**liquids**, the charge carriers are positive and negative ions. - In
**gases**, the charge carriers are positive ions and free electrons. - In
**semiconductors**, the charge carriers are holes and free electrons. - The conventional direction of the flow of current is opposite to the direction of the flow of electrons.
- Current is a scalar quantity.
- Current density is a vector quantity.
- The direction of current density
**j **is the same as that of electric field **E.** - Reciprocal of the slope of the
**V – I** graph is equal to the resistance. - The resistance of the conductor depends on the material of the conductor, shape, and size of the conductor as well as on the physical state (Temperature) of the conductor.
- Reciprocal of resistance is called conductance,
**g = 1 / R** - While calculating the resistance of a wire by the formula
**R = ρ*L / A** - If two resistances
**R**_{1} and **R**_{2} are in parallel, then the currents **I**_{1} and **I**_{2} in them will be distributed as**I**_{1} = **R**_{2 }I / (R_{1}_{ }+ R_{2})**I2** = **R**_{1}_{ }I / (R_{1}_{ }+ R_{2})- where
**I** is the net current that flows through the circuit.

- The total resistance of n equal resistances each of resistance r, in parallel, is:
**R = r / n**

- For n equal resistances
**R **_{series} / R _{parallel} = n^{2 }/ I

- The temperature coefficient of thermistors is negative and it is high.
- Resistivity increases with temperature.

https://www.gotomcqs.com/current-electricity/