shorts notes of physics ch 3

This chapter on Current Electricity explains the flow of charges and the laws governing electrical circuits. It begins with the definition of electric current, both average and instantaneous, and introduces the concept of drift velocity in conductors. The relation I=nqAvd connects current with charge density, area, and drift velocity. The notes also cover current density (J), mobility (μ), and how they relate to conductivity.

The section on resistance and Ohm’s law explains resistivity, conductivity, and how resistance varies with temperature. It then moves to electrical power and energy, showing formulas for heat generation in resistors. Kirchhoff’s laws are introduced: the junction law (conservation of charge) and the loop law (conservation of energy), which are essential for circuit analysis.

Further topics include series and parallel resistances, the Wheatstone bridge, and grouping of cells in series or parallel. The chapter also explains measuring instruments like ammeter and voltmeter, their construction, and working principles. Finally, it covers the potentiometer and metre bridge, highlighting their applications in measuring EMF, internal resistance, and unknown resistances.