Current Electricity
Unit 2. Covers Electric current and drift velocity; Ohm’s law and resistance; Electrical energy and power; Cells, emf and internal resistance; Kirchhoff’s rules and the Wheatstone bridge.
About this unit
This unit explains how charges flow through conductors. It covers electric current and drift velocity, Ohm’s law and resistivity, the heating and power of current, cells with emf and internal resistance, and Kirchhoff’s rules for analysing networks, including the Wheatstone bridge and meter bridge. Almost every electrical device you use, from a torch to a mobile charger, depends on these ideas.
How to prepare
- Memorise I = neAv_d, V = IR, R = ρL/A, P = VI = I²R = V²/R, V = E – Ir.
- Practise series/parallel resistor networks and Kirchhoff loop equations.
- Learn the balance condition P/Q = R/S and how the meter bridge uses it.
- Do unit conversions carefully: mm² to m², kWh to J (1 kWh = 3.6 × 10⁶ J).
- Revise how resistivity changes with temperature for metals and semiconductors.
Topics in this chapter
Electric current and drift velocity
Drift velocity, mobility and current.
5 questionsOhm’s law and resistance
V-I characteristics, resistivity, conductivity and temperature dependence.
6 questionsElectrical energy and power
Power dissipated in circuits.
5 questionsCells, emf and internal resistance
Combining cells in series and parallel.
6 questionsKirchhoff’s rules and the Wheatstone bridge
Analysing circuits.
5 questions