KTUYSBeta
Log inSign up

Cheat sheet · Class 12 · CBSE · Science Physics

Current Electricity cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

CBSE Class 12 · Physics

Cheat sheet

Chapter 3Current Electricity

Kirchhoff: junction rule (charge), loop rule (energy).

1. Basics

I=neAvdI = neAv_dV=IRV = IR
R=ρlAR = \rho\dfrac{l}{A}ρ=mne2τ\rho = \dfrac{m}{ne^2\tau}

Temperature: ρT=ρ0[1+α(T−T0)]\rho_T = \rho_0[1 + \alpha(T - T_0)].

2. Cells

V=ε−IrV = \varepsilon - Ir
I=εR+rI = \dfrac{\varepsilon}{R + r}
  • Series: ε=ε1+ε2\varepsilon = \varepsilon_1 + \varepsilon_2, r=r1+r2r = r_1 + r_2.
  • Parallel cells: equivalent emf is a weighted mean.

3. Networks

  • Series: R = R₁ + R₂; parallel: 1/R = 1/R₁ + 1/R₂.
  • Kirchhoff's junction rule: ΣI = 0; loop rule: ΣΔV = 0.
  • Wheatstone bridge balanced: P/Q = R/S.
P=VI=I2R=V2RP = VI = I^2R = \dfrac{V^2}{R}

4. Meter Bridge

RS=l100−l\dfrac{R}{S} = \dfrac{l}{100 - l}

5. Key Points

  • Drift velocity ~ 10⁻⁴ m/s.
  • Ohm's law fails for diodes.
  • Mobility μ = v_d / E.
  • Resistivity of metals rises with temperature.

Remember: I = neAv_d | V = ε − Ir | Kirchhoff | Wheatstone

Current Electricity: questions and notes

More Class 12 · CBSE · Science Physics cheat sheets

Practise Current Electricity

Sign up free to practise the full chapter. Questions you get wrong come back until you've mastered them.

Start practising free

Free to start · No credit card needed