alexcomicsland

我想問下electromotive force 同potential difference 有咩分別? 我見佢地有唔同ge定義，但學校notes 入面又話佢地係equals。咁即係掂?

thomas5843

electromotive force (e.m.f.) of a power supply is the amount of electrical potential energy gained by a coulomb of charge  which passes through the power supply
potential difference (p.d.) between 2 points is energy released when a unit of charge passes between these points
喺計數上係冇分別,單位都係volt or JC^-1, 但係concept 上係有好大分別
emf 係睇單一個cell pass through左之後gain左幾多energy
但係pd係睇兩個物件之間既差異, 個比較點可以係cell, 亦可以唔係, 而且係比較兩者之間小左幾多
所以我覺得你老師係錯concept
講真如果係冇分別, 人地點解要分開咁叫?

alexcomicsland

thx so much~~~

justin_ip

check wiki

https://en.wikipedia.org/wiki/Electromotive_force

https://en.wikipedia.org/wiki/Voltage

read it urself
hope u enjoy it

Constantine_161

引用:

原帖由 thomas5843 於 2015/10/24 05:25 PM 發表
electromotive force (e.m.f.) of a power supply is the amount of electrical potential energy gained by a coulomb of charge  which passes through the power supply
potential difference (p.d.) between 2  ...

Practically I would say that in calculation e.m.f. could be equal to p.d. in certain cases. The words come for different meanings...

I mean... well, e.m.f. is simply "the p.d. given by a power source such as a battery". But p.d. can be the potential difference between any two points specified (e.g. the p.d. between the "head" and the "tail" of a battery).

We don't say "the e.m.f. of the resistor is...". Instead, we say "the p.d. across the resistor is..."

Concise enough?

asd681

thx for sharing