VCE Physics Question Thread!

[Swagadaktal]

Oh wait a minute, made a silly mistake earlier as I was in a hurry.

The magnetic fields in the middle are pointing in the same direction. Along the west and east of conductor m and n, the magnetic fields cancel out partially, however it will never be zero. It does however approach to zero as you get further and further away, so I think that is what the question meant.

On a side note, you can actually make A the correct answer by orientating the third wire perpendicular m and n, making it parallel to the field produced.

When you say perpendicular you mean have the wire going into our out of the page right (the current)?
But in the question they assume it's just going flat across the page and hence the magnetic fields are added at that point?

Just trying to clarify my understanding here - will read this AOS during the upcoming week

thanks for help

EDIT: Added in question marks - coz grammar right?

[wyzard]

What I meant was having the wire lying flat on the paper, as shown in the attached image It's pretty difficult to describe 3D objects in space with words.

[Swagadaktal]

What I meant was having the wire lying flat on the paper, as shown in the attached image It's pretty difficult to describe 3D objects in space with words.

OOH yeah that's what I meant too soz, forgot that the wires were going in and out but yeah that's what I meant.

How would you diagramatically demonstrate the magnetic field? It's going in a circle around it right? so would you just draw a circle around the circle and put an arrow going anticlockwise for the one going outta page and a circle with an arrow going clockwise with the one going into the page?

Wanna get a perfect understanding of the fundamentals coz if I dont it's gonna bite me in the ass later on

[wyzard]

OOH yeah that's what I meant too soz, forgot that the wires were going in and out but yeah that's what I meant.

How would you diagramatically demonstrate the magnetic field? It's going in a circle around it right? so would you just draw a circle around the circle and put an arrow going anticlockwise for the one going outta page and a circle with an arrow going clockwise with the one going into the page?

Wanna get a perfect understanding of the fundamentals coz if I dont it's gonna bite me in the ass later on

Sure thing I've attached the sketch of the magnetic field line. They're not really circles as the fields produced by each wires are interfering with each other. Also notice how the middle field line is exactly straight? If you place a wire exactly on the field line, it will not experience any magnetic force.

A more detailed explanation can be found here: http://www.schoolphysics.co.uk/age16-19/Electricity%2520and%2520magnetism/Electromagnetism/text/Forces_between_currents/index.html

[Swagadaktal]

Sure thing I've attached the sketch of the magnetic field line. They're not really circles as the fields produced by each wires are interfering with each other. Also notice how the middle field line is exactly straight? If you place a wire exactly on the field line, it will not experience any magnetic force.

A more detailed explanation can be found here: http://www.schoolphysics.co.uk/age16-19/Electricity%2520and%2520magnetism/Electromagnetism/text/Forces_between_currents/index.html

thanks

[HopefulLawStudent]

Along the west and east of conductor m and n, the magnetic fields cancel out partially, however it will never be zero.

How do they cancel out partially?

[lzxnl]

From simple considerations of the magnetic field around a wire as a 1/r type magnetic field, it looks like if the two currents are the same, the field never cancel anywhere. They'll only cancel if the two currents are not the same.

What wyzard means is that if you have m on the left, n on the right and the currents are in opposite direction, the net magnetic field to the far left of m will have a contribution from current m and a contribution from current n in the opposite direction, so they'll somewhat cancel.

[HopefulLawStudent]

Someone please help. How do I find the direction of the induced current?

[zsteve]

Someone please help. How do I find the direction of the induced current?

Hey HLS:
Your wire is moving out of the page in a magnetic field. B is pointing to the left within the vicinity of the wire.

Using the RH palm rule and considering the positive charges in the wire:
- Point fingers in direction of B (i.e. to the left)
- Point thumb in direction of movement of +ve charges (i.e. out of the page)
- Palm gives direction in which +ve charges are 'pushed' (i.e. X -> Y)

Note that using the RH palm rule for negative charges (e.g. electrons) gives the opposite result. (as expected)

Hence current (flow of +ve charge) is from X to Y.

[HopefulLawStudent]

Got it. Thank you so much!

[HopefulLawStudent]

HALP PLS. Just for the flux-time graph question (part a).

[Swagadaktal]

HALP PLS. Just for the flux-time graph question.

Yo just gonna write from my understanding here - some physics legend is probably gonna comment underneath me and outdo me 1000 times but I still want the satisfaction hehe

No idea how to sketch but wouldnt the flux go in a U shape -
So
\----/ (it's negative on the axis coz the magnetic field lines are going into the page so gonna be negative right? Can someone confirm here...  soz about my shitty explanation lmao)

The induced voltage  follows the equation
induced voltage (E) = -dflux/dt
How do the physics people put those fancy equations in damn man im so underwhelming compared to them
So the induced voltage would look like
+ Horizontal line
                            0 gradient
                                               -ve horizontal line
If the flux is positive (I.e i got it wrong b4 hehe) then the signs are reversed...

tbh i think this helps me more than it helps you soz lmao <3
can someone teach me how to input those formulas for future purposes?

[Adequace]

Yeah, it's pretty much just a trapezium looking shape as Swag said. It doesn't have to be negative though because the direction that's being taken isn't specified.

Correct me if I'm wrong, I don't want to look like a bum and not a physics legend either 

[Swagadaktal]

Yeah, it's pretty much just a trapezium looking shape as Swag said. It doesn't have to be negative though because the direction that's being taken isn't specified.

Correct me if I'm wrong, I don't want to look like a bum and not a physics legend either 

Yeah I forgot what determines the sign - its just decided by the person right? What does the axis look like hls? Is it just a single quadrant?  I think my U should be positive.. .but then again no reason why it cant be negative if i wanna define it to be negative right?

[Adequace]

Yeah it's just decided by the person.

I accidently misread your comment. It isn't a U shape, it's literally a trapezium. It'll first be increasing at a constant rate, then it'll be constant (entire loop is in the magnetic field), then it'll decrease at a constant rate with the same magnitude as it did when it was increasing.

It shouldn't matter if the shape is positive or negative, it just shouldn't be in both from my understanding.