Electricity

This chapter builds the ideas of current electricity: electric current as the rate of flow of charge (I = Q/t), electric potential difference (V = W/Q), and how they are related by Ohm's law (V = IR). It examines resistance and the factors it depends on (length, area of cross-section and material, via R = rho l/A), the equivalent resistance of resistors in series and in parallel, and the heating effect of electric current (Joule's law H = I^2 Rt) together with electric power (P = VI = I^2 R = V^2/R) and its everyday applications such as fuses and the kilowatt-hour.