[2019 DSE] Physics 物理 操題區
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真係好多野背
讀到想死
寫notes都寫左成本書
讀到想死
寫notes都寫左成本書
學校啊sir太廢 今年自修剩係睇radian
感覺有進步
感覺有進步
btw 識做mc一定識做lq
呼籲大家操mc 清concept
呼籲大家操mc 清concept
B
點解？邊一條wire 係live wire? Yellow green?
Right hand rule, direction of your thumb pointing is the cure direction, and the curl of your four fingers are the direction of B field.
有冇巴打有2018嘅atomic world#adore 網上好似冇
搞錯 係冇astronomy
好
Got it, then the blue wire is extra. Hence the answer is D
Use lenz law and right hand rule solve this question
YouTube HhFZfWLl-P0
YouTube HhFZfWLl-P0
多余咁解
lenz law+ right hand rule
induced current=傲嬌，
你行近又叫你走，你話走又會留你
正常講法係induced current 係oppose the change
你代入個角色（你係個coil)
case one 係 收到愈來愈多 圓點 B-field,
所以induced current 會produce 交叉 B-field to oppose the change
之後應該明
你行近又叫你走，你話走又會留你
正常講法係induced current 係oppose the change
你代入個角色（你係個coil)
case one 係 收到愈來愈多 圓點 B-field,
所以induced current 會produce 交叉 B-field to oppose the change
之後應該明
1. Lenz law - Lenz's law states that when an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such, that it produces an current that's magnetic field opposes the change which produces it
2. EMF formula emf= -(N delta(phi)) / delta t
N= number of coil in a wire,
delta(phi) = change in external magnetic flux
delta t = change in time.
3. Inducted Magnetic flux = delta(phi) induced
therefore
(i) the rectangular loop move toward right, which experiences increase in external magnetic flux that is coming out of the page, so by the emf formula in 2. the induced magnetic flux is going to oppose the increase in external magnetic field. Hence applying the right hand rule to rectangular loop wire closest to the straight wire, the induced current in the rectangular loop will give rise to the induced magnetic flux that opposes the increase of the magnetic flux. So since the straight wire magnetic flux is out of the page, then induced magnetic flux is to oppose which is going into the page. taking the right side of the rectangular loop for right hand rule, the induced current is flowing from top to bottom to create the magnetic flux flowing into the page, so from the current flow direction at the right side from top to bottom, we can deduced that the current flow in the rectangular loop is counter clockwise.
The key to understand is this:
Relation between External Magnetic Field (flux) is always Opposite with the Induced Magnetic Field so as to achieve equilibrium.
Once you developed the this idea, apply it to the question. if you have a change in magnetic flux that is increasing stronger, then you will have the induced magnetic flux that is to oppose the stronger external magnetic field. so when external magnetic flux is going out of the page, then the induced magnetic flux must be going into the page (opposite) then apply right hand rule to find out the current direction. easy peasy.
(ii) and (iii) are also using the same principle.
2. EMF formula emf= -(N delta(phi)) / delta t
N= number of coil in a wire,
delta(phi) = change in external magnetic flux
delta t = change in time.
3. Inducted Magnetic flux = delta(phi) induced
therefore
(i) the rectangular loop move toward right, which experiences increase in external magnetic flux that is coming out of the page, so by the emf formula in 2. the induced magnetic flux is going to oppose the increase in external magnetic field. Hence applying the right hand rule to rectangular loop wire closest to the straight wire, the induced current in the rectangular loop will give rise to the induced magnetic flux that opposes the increase of the magnetic flux. So since the straight wire magnetic flux is out of the page, then induced magnetic flux is to oppose which is going into the page. taking the right side of the rectangular loop for right hand rule, the induced current is flowing from top to bottom to create the magnetic flux flowing into the page, so from the current flow direction at the right side from top to bottom, we can deduced that the current flow in the rectangular loop is counter clockwise.
The key to understand is this:
Relation between External Magnetic Field (flux) is always Opposite with the Induced Magnetic Field so as to achieve equilibrium.
Once you developed the this idea, apply it to the question. if you have a change in magnetic flux that is increasing stronger, then you will have the induced magnetic flux that is to oppose the stronger external magnetic field. so when external magnetic flux is going out of the page, then the induced magnetic flux must be going into the page (opposite) then apply right hand rule to find out the current direction. easy peasy.
(ii) and (iii) are also using the same principle.