求大神救小弟一命，分析一下这段话句型、从句神马的，内容是专业英语，不需要翻译太准确，只要告诉我哪个句子是啥从句就够了
If you look at a catalogue of electronic components you'll find an enormous variety of sizes and types of capacitor.However, for most purposes we can divide capacitors into two basic types: dielectric and electrolytic.
A capacitor acts as a charge store (Figure 1-4). It contains a pair of metal plates separated by a thin sheet of insulating material. The plates are electrically neutral - the number of positive protons in each exactly equals the number of negative electrons.
However, if we connect wires to the plates and apply external voltage we can drag electrons off one plate and push them on to the other.
If you look at a catalogue of electronic components you'll find an enormous variety of sizes and types of capacitor.However, for most purposes we can divide capacitors into two basic types: dielectric and electrolytic.
A capacitor acts as a charge store (Figure 1-4). It contains a pair of metal plates separated by a thin sheet of insulating material. The plates are electrically neutral - the number of positive protons in each exactly equals the number of negative electrons.
However, if we connect wires to the plates and apply external voltage we can drag electrons off one plate and push them on to the other.
