Basic Electrical Formulas

$V=\frac WQ$

V= Electric Potential, Q= Charge, W= Electric potential energy

$I=\frac qt =\frac {n e}{t}$

I = Current, q = Charge, t = time, n = number of electrons, $e = -1.6\times10^{-19}$

$I= n eAv_d$

n = number of electrons per unit volume, $e = -1.6\times10^{-19}$ , A= area of cross-section of the wire, $v_d$ = drift velocity of free electrons

$R=\rho \frac lA$

R= Resistance, $\rho$ =Resistivity or specific resistance, l= length, A= cross-section area

$G=\frac 1R$

G= Conductance, R= Resistance

$R_1= R_0(1+\alpha_0t_1)$

A metallic conductor having resistance $R_0$ at $0^{o}C$ and $R_1$ at $t_{1}^{o}C, \alpha _{0}=$ Temperature coefficient of resistance at $0^{o}C$

$\alpha _{1} = \frac{\alpha _{0}}{1+\alpha _{0}t_{1}}$

$\alpha _{1}$ = Temperature coefficient of resistance at $t_{1}^{o}C$
$\alpha _{0}$ = Temperature coefficient of resistance at $0^{o}C$

$R_2= R_1[1+\alpha _{1}(t_{2}-t_{1})]$

Conductor having resistance $R_2$ at $t_{2}^{o}C$ and $R_1$ at $t_{1}^{o}C$ , $\alpha _{1}$ = Temperature coefficient of resistance at $t_{1}^{o}C$

$V= IR$

V= Potential Difference, I= Current, R= Resistance

$P= VI=I^{2}R=\frac{V^{2}}{R}$

P= Electric Power, V= Potential Difference, I= Current, R= Resistance

$W=Pt= VIt=I^{2}Rt=\frac{V^{2}t}{R}$

W= Electrical energy consumed, P= Electric Power, t= energy consumed time, V= Potential Difference, I= Current, R= Resistance

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