help with a question (1 Viewer)

[sarbear.h]

can someone help with hsc 2010 q20
edit: btw i checked the physics high yt vid... they used the right hand curl rule which i totally agree with except with like answer A he said the left was the south???? is it not the north???

 

[cheesynooby]

current flows for pos to neg so in (A) the coils of wire can be thought of as a solenoid that forms an electromagnet with N pole to the left. i.e. the B field across the armature is to the left.
following the + terminal leads to the right brush - so this is always +ve. because of the split ring commutator the right side of the armature is also always +ve. using the right hand rule, with I going into page, B to left, the F is up and the armature rotates anticlockwise.
B is the same as A except the brushes are switched so the armature rotates clockwise.
in C and D the right magnet and left electromagnet form north poles facing each other so there is no uniform B field and can be discarded.
edit: the left acts as the south pole for the armature because current flows up the side facing u and down the other side - so the N pole is on the left. thus the S pole is on the right of the magnet on the left which is what receives the B field experienced by the armature

 

[alphxreturns]

first we want the magnetic field to run N to S, alternatively S to N (for uniform B field)

using the right hand screw rule for looped current, we see that the left magnet thing will have a magnetic field with North going left (thus south going right)

so, in the right magnet, we want a similar north-going-left magnetic field. use the right hand rule again to see that both C and D have a north-going-right field.

We are left with A and B, the difference between them being in which side to link the positive and negative terminals to.

as seen in the diagrams we want a certain rotation result: counter-clockwise

use the right hand palm rule, to, if the B-field was going right to left, see what direction of current would give us the right force to cause this rotation

ok nvm cheesynoby got this under control

 

[sarbear.h]

current flows for pos to neg so in (A) the coils of wire can be thought of as a solenoid that forms an electromagnet with N pole to the left. i.e. the B field across the armature is to the left.
following the + terminal leads to the right brush - so this is always +ve. because of the split ring commutator the right side of the armature is also always +ve. using the right hand rule, with I going into page, B to left, the F is up and the armature rotates anticlockwise.
B is the same as A except the brushes are switched so the armature rotates clockwise.
in C and D the right magnet and left electromagnet form north poles facing each other so there is no uniform B field and can be discarded.
edit: the left acts as the south pole for the armature because current flows up the side facing u and down the other side - so the N pole is on the left. thus the S pole is on the right of the magnet on the left which is what receives the B field experienced by the armature

first we want the magnetic field to run N to S, alternatively S to N (for uniform B field)

using the right hand screw rule for looped current, we see that the left magnet thing will have a magnetic field with North going left (thus south going right)

so, in the right magnet, we want a similar north-going-left magnetic field. use the right hand rule again to see that both C and D have a north-going-right field.

We are left with A and B, the difference between them being in which side to link the positive and negative terminals to.

as seen in the diagrams we want a certain rotation result: counter-clockwise

use the right hand palm rule, to, if the B-field was going right to left, see what direction of current would give us the right force to cause this rotation

ok nvm cheesynoby got this under control

yeah bc thats what i thought like if ur using the right hand curl rule then for like A, the north will be left south be right
bruh phys high got me messed up

 

[sarbear.h]

current flows for pos to neg so in (A) the coils of wire can be thought of as a solenoid that forms an electromagnet with N pole to the left. i.e. the B field across the armature is to the left.
following the + terminal leads to the right brush - so this is always +ve. because of the split ring commutator the right side of the armature is also always +ve. using the right hand rule, with I going into page, B to left, the F is up and the armature rotates anticlockwise.
B is the same as A except the brushes are switched so the armature rotates clockwise.
in C and D the right magnet and left electromagnet form north poles facing each other so there is no uniform B field and can be discarded.
edit: the left acts as the south pole for the armature because current flows up the side facing u and down the other side - so the N pole is on the left. thus the S pole is on the right of the magnet on the left which is what receives the B field experienced by the armature

u said that the split right commutator on the right side of the armature is always +ve? but answer B.. the pos side isnt connected to the right brush...? or is what u said only applicable for ans A

lowkey this still dont make sense.. i only get why A isn't the answer

 

[cheesynooby]

u said that the split right commutator on the right side of the armature is always +ve? but answer B.. the pos side isnt connected to the right brush...? or is what u said only applicable for ans A

lowkey this still dont make sense.. i only get why A isn't the answer

yeah in B, the pos and neg terminals connected to opposite brushes from A
i.e. pos on left brush, neg on right brush
B field is still to the left
and in the rotor coil the I goes clockwise so force is up on the left side and down on the right side -> clockwise

 

[yourlocaliga]

can someone help with hsc 2010 q20
edit: btw i checked the physics high yt vid... they used the right hand curl rule which i totally agree with except with like answer A he said the left was the south???? is it not the north???
View attachment 47040

YOU SAID YOU WOULD MAKE A NEW ACCOUNT

 

[sarbear.h]

YOU SAID YOU WOULD MAKE A NEW ACCOUNT

u exposed ur own bos account-