[2019 DSE] Physics 物理 操題區

https://youtu.be/gaPf3zhQMXI

我解釋你聽點用 lenz law

grip rule= 手指公豎出黎嗰個
right-hand rule=三隻手指嗰個

向下所以就clockwise?

先combine兩個e.m.f.
就決定到current方向

睇左前面嗰d
冇睇後面past paper嗰度
但係有樣唔明
你話要closed circuit先有current
如果應用番喺上面嗰題
即係要有個circuit駁住個rectangular loop先有current?

左手係有force,有b-field,繼而得出current
右手係有b-field,有current,繼而得出force?

rectangular loop本身就係一個closed circuit
induced e.m.f.可以當係一個電池

左右調轉左

左手個主角係力；右手個主角係current

原來係咁
即係closed loop->有current,有emf
open loop->冇current，有emf

即係一條直既wire carrying a current就自自然然會有force
因為有current->有b-field
有齊current,b-field就有force

yes

唔係
個wire同唔到自己整出黎既b-field interact
要有外來既b-field先有force

哦
即係要人地比既b-field先可以induce到force
自己current induce出黎既b-field就唔得

有,不過基本上淨係識mechanics

點解又唔岩??

有external magnetic field, current
根據left-hand rule, force is induced
After force is induced, using right-hand rule, current is induced which points downwards
岩唔岩?

back emf out-c