$$\bullet$$ Electric Current:
$$I = \dfrac{Q}{t}$$
$$\text{(Q= Electric charge and t = Time)}$$

$$\bullet$$ Electric potential difference:

$$V = \dfrac{W}{q}$$
$$\text{(W = Work done)}$$

$$\bullet$$ Ohm's law:

$$V = IR$$ $$\left|\begin{matrix}\!\!\!\!\! V \ \text{is the volatge}\\ \!\!\!\!\! I \ \text {is the current} \\R \ \text{is the resistance} \end{matrix}\right.$$

$$\bullet$$ Resistance of a material:

$$R = \rho \dfrac{l}{A}$$ $$\left|\begin{matrix}\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\! \rho \ \text{is the resistivity}\\ \!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\! l \ \text {is the length of the object} \\A \ \text{is the cross-sectional area of the object} \end{matrix}\right.$$

$$\bullet$$ Connection of resistances:

$$R_{eq} = R_1 + R_2 + R_3+ ...$$ (for series connection)

$$\dfrac{1}{R_{eq}} =\dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3}+...$$ (for parallel connection)

$$\bullet$$ Joule's law of heating: 
$$H =VIt =I^2Rt=\dfrac{V^2t}{R}$$

$$\bullet$$ Electric power:
$$P=VI = I^2R = \dfrac{V^2}{R}$$

Electricity