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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- CSIR NET
- Physical Sciences
)A long solenoid is embedded in a conducting medium and is insulated from the medium. If the current through the solenoid is increased at a constant rate, the i
Magnetic field outside a solenoid is zero. How the question is even valid?
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Sanchari Pal
Why Electric field is proportional to emf? as integration( E. dl) =Emf. then E*2pi*r =Emf. and now this EMf is proportional to the current. means only right hand side should be proportional to the current
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Paltu Sen
You just imagine a circular disc of radius r, perpendicular to the axis of the cylinder and find the magnetic flux through this disc. For better understanding you can study Griffiths electrodynamics book
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Paltu Sen
1.The induced current is proportional to induced emf which is proportional to induced circumferential electric field here. 2. Since the value of B is nonzero inside the solenoid we take the limit in 2nd case upto R but not upto r
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Sanchari Pal
first of all the 1)induced current is asked not the Electric fied 2)2ndly the value of B = (neu)o nI is valid inside the solenoid not outside it. then? how is this response is valid
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Paltu Sen Best Answer
ans) opt-d
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Paltu Sen![best-answer]()
Great!! you have pointed out the right thing...In question they should mention the current through which portion of the conducting medium. Here we are actually getting a volume current density. Nevertheless we consider a current flow through a circular ring (torus shaped)of the conducting medium having mean radius r and cross-sectional area A , we r getting I= emf/R. Here R= l/(sigma. A)=(2*pi*r)/(sigma*A). So, I proportional to (emf/2*pi*r) i.e. proportional to induced electric field