1i think the ans. is [d]
2 circular loops of equal radii are placed coaxially at some separation.
The first is cut and a battery is inserted to drive a curent in it .
The current changes slightly due to the variation in resistance with temperature.
During this period , the loops ,
[a]attract each oder
[b) Repel each oder
[c] do not exert any force on each oder
[d]attract or repel each other depending on the sense of the current .
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15 Answers
23i also feel d , buttttttttttttttttttttttttttt HCV ne a diya hai [2][2][2][2]
1Sense of current is not required.
Whichever direction the current flows, there will be a magnetic field set up in the first coil. As the question states, this field is a changing one, so the magnetic flux linked with this coil also changes.
A change in flux is caused in the second coil, due to mutual induction. Hence a current is induced such that it opposes the change in flux. Hence if the first coil has current in clockwise direction, a current is induced in anti clockwise direction.
Hence if the first coil is a North pole, the induced coil will also become a North pole.
It is guaranteed that current will flow in the second coil since there is resistance of the coil.
So whatever the direction of current, the loops should repel because the sides of the loops which face each other are like poles (of the magnet-like coil).
Hence right answer should be B.
1I didn't expect HCV to do this much keeda. I think answer can be A but I am not able to find sufficient reasoning.
106The current changes slightly due to the variation in resistance with temperature.
so current decreases with time as temp increases leading to increase of resistance.
So if the current which produces mag field is clockwise i.e. S pole, then induced current will be anticlockwise i.e. N pole, as magnitude of clockwise current is decreasing and vice-versa.
Hence the two coils will attract each other.
23Yes asish , your reason is correct .
ankur i dont agree,
Thus if current in supper loop decreasing , loops will attract , if current in upper loop is increasing , loops will repel
106qwerty: are you just telling general theory or r u talking about this particular problem?? for this problem ans is ALWAYS ATTRACT
23asish , it will attract only if current in upper loop decreases na ???
actually i couldnt agree with ankur's #4 post , hence i made my point . Since u cleared that current in upper loop decreases , of course due to the thermal energy produced , then loops will attract .
106acc to question naa...
that's what it clearly mentions that there is change in current due to effect of temperature. i.e. current decreases here..
1no but it is not mentioned anywhere whether the temp. is increasing or decreasing
23temp will increase since thermal energy is produced as current passes thorugh the resistance
1Hey..Qwerty... i made a mistake there... i mistook the coils to be placed at a distance from each other, not coaxially.
Only for loops placed at a distance with their centres along the same axis, my answer applies.
But if the coils are placed coaxially, then asish's answer is correct.
Due to change in current (increasing or decreasing) in outer coil, an oppositely directed current is induced in the inner coil, hence the coils attract.
1can sum1 explain to me y the current produced in the 2nd coil will always be opposite to that in the 1st
23ankur , the coils are placed coaxially at some distance frm each oder