## A-Level H2 物理筆記

## Chapter 17: Current of Electricity

## 章节主题：

Conventional current and electron flow

Electromotive force

Potential difference

Resistance

## 学习目标：

(a) State that current is a rate of flow of charge and that it is measured in amperes.

(b) Distinguish between conventional current and electron flow.

(c) Recall and apply the relationship charge = current × time to new situations or to solve related problems.

(d) Define electromotive force (e.m.f.) as the work done by a source in driving unit charge around a complete circuit.

(e) Calculate the total e.m.f. where several sources are arranged in series.

(f) State that the e.m.f. of a source and the potential difference (p.d.) across a circuit component are measured in volts.

(g) Define the p.d. across a component in a circuit as the work done to drive unit charge through the component.

(h) State the definition that resistance = p.d./ current.

(i) Apply the relationship R = V/ I to new situations or to solve related problems.

(j) Describe an experiment to determine the resistance of a metallic conductor using a voltmeter and an ammeter, and make the necessary calculations.

(k) Recall and apply the formulae for the effective resistance of a number of resistors in series and in parallel to new situations or to solve related problems.

(l) Recall and apply the relationship of the proportionality between resistance and the length and cross-sectional area of a wire to new situations or to solve related problems.

(m) State Ohm’s Law.

(n) Describe the effect of temperature increase on the resistance of a metallic conductor.

(o) Sketch and interpret the I /V characteristic graphs for a metallic conductor at constant temperature, for a filament lamp and for a semiconductor diode.