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physics A-Level Physics
 
Solved problems for the chapter:
 

Magnetic Flux

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Detailed solution steps are available at:
 
https://en.openprof.com/wb/chapter:magnetic_flux/4485/


Example 1.

A circular loop with a radius of 10 cm is placed in a homogeneous magnetic field of flux density of 0.8 T so that the plane of the loop is perpendicular to the field forces. Calculate the magnetic flux.

    
Example 2.

The table below shows the relative permeability values of different materials. A cylindrical material, with the listed permeability, is placed in a coil 30 cm long and is surrounded by 200 turns of wire through which a current of 3 A flows.

  • Identify which of the following materials is a ferromagnet, paramagnet or diamagnet.

  • What is the magnetic flux density inside an individual cylinder made of ferromagnetic material when it is in the coil?


MaterialRelative permeability () 
Iron (Fe)5000 
Aluminium (Al)1.000022 
Nickel (Ni)400 
Copper (Cu)0.999994 
Platinum (Pt)1.000265 
Cobalt (Co)3200 

    
3.

A circular loop with a radius of 15 cm is placed in a homogeneous magnetic field of flux density 1.2 T so that the magnetic field forces do not pierce its plane. The loop is rotated through an angle around an axis perpendicular to the lines. Calculate the magnetic flux through the loop.

    
4.

A cylinder is made of a homogeneous material with permeability, and is tightly fitted in a coil. Calculate the permeability of the material when the cylinder is pushed into the coil and makes the magnetic flux density of the coil to be reduced by 0.1%.

    
5.

A square loop with a side length of 30 cm is placed in a homogeneous magnetic field of flux density of 0.8 T so that the field forces are perpendicular to its plane. Calculate the angle of rotation of the loop if the magnetic flux through the loop is 0.050 Wb.

    
6.

A coil of length 50 cm is wound with 1000 turns round an alloy rod of Iron and Cobalt. Calculate the current that must flow through the coil to have a magnetic field with a flux density of 2 T in the rod?


The relative permeability of the alloy is 18000 and the permeability of free space .

    
7.

A rectangular loop with sides lengths l = 10 cm and b = 20 cm is placed in a homogeneous magnetic field so that the field forces pierce its plane at right angles.

  • Calculate the magnetic field density if the magnetic flux through the surface is 0.5 mWb.

  • Calculate the change in magnetic flux if the loop is rotated by .


    
8.

Calculate the relative permeability of a substance in a long coil with 1500 turns per meter of length if a current of 2 A in the coil creates a magnetic flux density of 3 T.


The permeability of free space .