Hand written note of current electricity

Current electricity is the study of the steady flow of electric charge through a conductor. It deals with concepts like electric current, which is the rate of flow of charge measured in amperes, and drift velocity, the average velocity of free electrons under an electric field. Ohm’s Law forms the foundation, stating that the current through a conductor is directly proportional to the potential difference across it, provided temperature remains constant, and it introduces resistance as the opposition to flow. Resistivity and conductivity are material-specific properties that determine how easily charge moves, and they depend on temperature. The chapter also covers combinations of resistors in series and parallel, which affect the equivalent resistance and total current in a circuit. Kirchhoff’s laws are essential for analyzing complex circuits: Kirchhoff’s Current Law states that the total current entering a junction equals the total current leaving it, while Kirchhoff’s Voltage Law says the sum of all potential differences in a closed loop is zero. Cells and batteries are discussed as sources of emf, along with internal resistance and grouping of cells to obtain desired voltage and current. The Wheatstone bridge and potentiometer are important applications for measuring unknown resistance and comparing emfs with high accuracy. Heating effects of current are explained by Joule’s law, where electrical energy is converted into heat, leading to concepts like electric power. Finally, the chapter introduces the concept of electric energy and its commercial unit, the kilowatt-hour, linking physics to everyday applications.