A-Level物理的評分標準，物理考試如其它考試一樣,也采取全球標準化評分,總分600分。所有考試分為六個單元,其中 1、 2、 4、 5單元的卷面分值均為80分,標準化之后的滿分為 120分; 第3、6兩個實驗單元卷面分值為 40分,標準化之后的滿分為 60分?？偝煽冞_到標準化分數(shù) 80%以上的即 A 等(480分以上),B、C、D、E、U 分別對應(yīng)總成績的70-80%、60-70%、50-60%、40-50%及40%以下。

接下來留學(xué)生輔導(dǎo)老師給大家說下，ALevel物理輔導(dǎo)-電容器Capacitors的知識。

Revision: Capacitors

A capacitor is a device used to store charge.

They can also store energy,in the form of electrical energy due to the electrical field that is generated between the charged plates.

When in a circuit containing a cell and a resistor capacitors collect charge on these plates. One plate collects positive charge and the other collects negative charge. You may therefore say that a capacitors overall charge is 0 as the plates cancel out. Well not quite as when we talk about the charge a capacitor holds we refer to the amount on just ONE of the plates.

Circuit symbols for capacitors

They are made of two parallel metal plates which are separated by an insulting material called a dielectric. These are two types of main capacitor,electrolytic and non-electrolytic.

Electrolytic capacitors can store a greater amount of charge but are polarized (have a +ve and -ve lead) and therefore must be connected in the correct way. Reversing the polarities of an electrolytic capacitor results in their being damaged and possibly exploding.

Non-electrolytic capacitors store slightly less charge but are not polarized and can be connected anywhere in a circuit.