GCE A-Level Physics Syllabus
Chapter 14: Current of Electricity
Resistance and resistivity
(a) Show an understanding that electric current is the rate of flow of charge.
(b) Derive and use the equation I = nAvq for a current-carrying conductor, where n is the number density of charge carriers and v is the drift velocity.
(c) Recall and solve problems using the equation Q = It
(d) Recall and solve problems using the equation V = W/Q
(e) Recall and solve problems using the equations P = VI, P = I²R and P = V²/R.
(f) Define the resistance of a circuit component as the ratio of the potential difference across the component to the current passing through it and solve problems using the equation V = IR.
(g) Sketch and explain the I–V characteristics of various electrical components such as an ohmic resistor, a semiconductor diode, a filament lamp and a negative temperature coefficient (NTC) thermistor.
(h) Sketch the resistance-temperature characteristic of an NTC thermistor.
(i) Recall and solve problems using the equation R =ρl/A.
(j) Distinguish between electromotive force (e.m.f.) and potential difference (p.d.) using energy considerations.
(k) Show an understanding of the effects of the internal resistance of a source of e.m.f. on the terminal potential difference and output power.