Current Electricity & Circuits

• Derive Ohm's law from electron drift velocity and relaxation time: I = n e A v_d.
• Calculate temperature coefficient of resistance for metals and semiconductors.
• Formulate junction and loop equations using Kirchhoff's rules for multi-mesh circuits.
• Analyze balanced Wheatstone bridge conditions and metre bridge unknown resistance measurement.

• Drift Velocity (v_d = -eEτ/m) & Current Density (J = σE)
• Resistivity & Temperature Dependence (R_T = R_0(1 + αΔT))
• EMF, Internal Resistance & Terminal Potential Difference
• Kirchhoff's Current Law (KCL) & Voltage Law (KVL)
• Wheatstone Bridge Balance Condition (P/Q = R/S)

“KCL represents charge conservation; KVL represents energy conservation in a closed electrical loop.”

• •Internal resistance causes terminal potential V = E - Ir when discharging, V = E + Ir when charging.
• •Maximum power transfer theorem: maximum power delivered to load when R = r.
• •Potentiometer draws zero current at null point, measuring true EMF.

Extensive circuit solving with Kirchhoff's mesh analysis, symmetry reduction, and internal resistance.