Current Electricity

(1) Kirchoff’s Law: (i) ΣI = 0 (ii) ΣIR + ΣE = 0

(2) Wheatstone’s network: Balanced condition,

${R_1}/{R_2} = {R_3}/{R_4}$

(3) $R = ρ l/A$

(4) Meter Bridge:
(i) $X/R = l_x/l_R$
(ii) Kelvin’s Method, ${G}/{R} = l_G/l_R$

(5) Potential Gradient: $V/L = k$

(6) I (r+R) = E

(7) $σ = R/L$

(8) E = k l

(9) $E_1/E_2 = {l_1 + l_2}/{l_1 – l_2}$

(10) $r = R({l_1 – l_2}/{l_2})$     r -> internal resistance of cell