MCQ question - help (1 Viewer)

[iStudent]

Also explain your answer please

 

[mitchmiles]

not a professional at this but id answer D: No change to the strength of the detected magnetic field within the loop.

the loop of wire doesn't have a current running through it. therefore, it would have no effect on the magnetic field

i might be wrong but yeah..

 

[iStudent]

Nope, sorry =/
Anyone else?

 

[iStudent]

I think this is the hardest physics MCQ I've seen in my life

 

[Chris100]

Is it A

 

[iStudent]

Nope, it's B
Now try and think of an explanation ... (I personally think it's A as well, but this exam paper usually doesn't have mistakes ...)

 

[mysterymarkplz]

If the answer is B all i can think of is eddy currents, its a loop of wire so if you move it within a magnetic field it'll produce eddy currents within the loop of wire, the eddy currents itself generate a magnetic field, causing the detector to detect the magnetic field coming out from earth and the magnetic field generated from the eddy currents.
Other than that i can't pull anything else out of my ass.

 

[mysterymarkplz]

Btw what paper is this? thats a pretty weird question

 

[Chris100]

What no, it's A. My friend asked me this question and my answer was right, confirmed with physics tutor as well
can you pls recheck your solution document, am panicking right now

 

[mysterymarkplz]

I don't think its A, all the answers end with, "WITHIN THE LOOP", if you were taking lenz's law into account then it should produce a magnetic field which opposes the motion of the change of shape in coil, so it should repel Earth's south pole, so if a magnetic field detector was used in that vicinity then the magnetic field before the change in shape to after the change in shape should be smaller, but its talking about within the loop, theres definitely eddy currents being induced so the loop goes to emitting 0 tesla to emitting x tesla where x>0 purely due to the presence of eddy currents.

 

[iStudent]

Exam Choice 2012
ah yes, the answer is A my bad
now explain your answer please

I read into the question so much I thoguht A = increasing B = decreasing

 

[QZP]

If the answer is B all i can think of is eddy currents, its a loop of wire so if you move it within a magnetic field it'll produce eddy currents within the loop of wire, the eddy currents itself generate a magnetic field, causing the detector to detect the magnetic field coming out from earth and the magnetic field generated from the eddy currents.
Other than that i can't pull anything else out of my ass.

I don't think its A, all the answers end with, "WITHIN THE LOOP", if you were taking lenz's law into account then it should produce a magnetic field which opposes the motion of the change of shape in coil, so it should repel Earth's south pole, so if a magnetic field detector was used in that vicinity then the magnetic field before the change in shape to after the change in shape should be smaller, but its talking about within the loop, theres definitely eddy currents being induced so the loop goes to emitting 0 tesla to emitting x tesla where x>0 purely due to the presence of eddy currents.

eddy currents LOL good one hahaha

 

[sleepyair]

If the answer is B all i can think of is eddy currents, its a loop of wire so if you move it within a magnetic field it'll produce eddy currents within the loop of wire, the eddy currents itself generate a magnetic field, causing the detector to detect the magnetic field coming out from earth and the magnetic field generated from the eddy currents.
Other than that i can't pull anything else out of my ass.

QZP is right. Eddy currents only occur in solid conductors.

 

[xGhanem]

Wait, so is it because of eddy currents?

EDIT: Ah okay, no.

 

[QZP]

I don't like how it says "It is then allowed to go back to it's original shape" which creates confusion.

 

[Chris100]

Exam Choice 2012
ah yes, the answer is A my bad
now explain your answer please

I read into the question so much I thoguht A = increasing B = decreasing

Just try replacing the south pole of the Earth with the south pole of a normal magnet. This helped me understand and visualise the question better, after you get a clear image of what's happening, the explanation to A should come pretty quickly

 

[iStudent]

Can you explain further... btw the earth's south Pole is actually a north pole

 

[obliviousninja]

Im no physist, but I got A.

 

[Chris100]

It doesn't matter which pole you imagine it to be, you'll still get the same answer

 

[iStudent]

I still don't know how to do it.. can someone explain it please?
What I know so far is that a current is induced in the wire due to lenz's law. but if I use the right hand grip rule, I find that the magnetic field strength increases...
or did I get this entirely wrong