{ "metadata": { "name": "", "signature": "sha256:a79be9375f475037255b00d45fe0971e7606cfc4e70e2a086d7c77b20c6b87d7" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter10:MAGNETIC PROPERTIES OF MATERIALS" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.1:pg-288" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate permeability and susceptibility of the bar\n", "phi=2.4*10**-5 #magnetic flux in weber\n", "A=0.2*10**-4 #cross sectional area in m**2\n", "B=phi/A #magnetic induction in N/Am\n", "H=1200 #magnetising field in A/m\n", "mu=B/H\n", "print \"permeability is mu=\",\"{:.2e}\".format(mu),\"N/A**2\"\n", "muo=4*math.pi*10**-7 \n", "chim=(mu/muo)-1\n", "print \"susceptibility is chim=\",round(chim,2),\"unitless\"\n", "#the answer is given wrong in the book (round off error) chim=737\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "permeability is mu= 1.00e-03 N/A**2\n", "susceptibility is chim= 794.77 unitless\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.2:pg-289" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate current should be sent through the solenoid\n", "l=.10 #length in m\n", "N=50 #number of turns\n", "H=5*10**3 #magnetising field in A/m\n", "i=H*l/N \n", "print \"current is i=\",i,\"A\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "current is i= 10.0 A\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.3:pg-289" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate magnetic moment of the rod\n", "#formula is B=muo*(H+I)\n", "#where H=ni\n", "n=500.0 #number of turns in turns/m\n", "i=0.5 #current passed through the solenoid in A\n", "mur=1200.0 #relative permeability\n", "I=(mur-1)*n*i #intensity of magnetisation in A/m\n", "V=10**-3 #volume in m**3\n", "M=I*V\n", "print \"the magnetic moment of the rod is M=\",round(M),\"A-m**2\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "the magnetic moment of the rod is M= 300.0 A-m**2\n" ] } ], "prompt_number": 1 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.4:pg-290" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate flux density,magnetic intensity,permeability of iron\n", "phi=2.0*10**-6 #flux in the ring in weber\n", "A=10**-4 #cross-sectional area in m**2\n", "B=phi/A \n", "print \"flux density is B=\",\"{:.2e}\".format(B),\"weber/m**2\"\n", "N=200.0 #number of turns\n", "i=0.30 #current flows in the windings in A\n", "l=0.2 #length in m\n", "H=N*i/l\n", "print \"magnetic intensity is H=\",H,\"A-turn/m\"\n", "mu=B/H\n", "print \"permeability is mu=\",round(mu,6),\"weber/A-m\"\n", "muo=4*math.pi*10**-7 \n", "mur=mu/muo\n", "print \"relative permeability is mur=\",round(mur,2),\"unitless\"\n", "\n", "#the answer for H in the book is wrong\n", "#the answer for mu in book is wrong due to wrong H\n", "#the answer in book for mur is wrong due to \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "flux density is B= 2.00e-02 weber/m**2\n", "magnetic intensity is H= 300.0 A-turn/m\n", "permeability is mu= 6.7e-05 weber/A-m\n", "relative permeability is mur= 53.05 unitless\n" ] } ], "prompt_number": 3 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.5:pg-294" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate number of ampere turns\n", "l=0.5 #length in m\n", "mu=6.5*10**-3 #permeability of iron in henry/m\n", "A=2*10**-4 #area of cross-section in m**-4\n", "R=l/(mu*A) #reluctance in A-turns/weber\n", "flux=4*10**-4 #in weber\n", "mmf=flux*R\n", "print \"the number of ampere turns is mmf=\",round(mmf,1),\"ampere-turns\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "the number of ampere turns is mmf= 153.8 ampere-turns\n" ] } ], "prompt_number": 9 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.6:pg-294" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate relative permeability of the medium\n", "phi=1.5*10**-3 #magnetic flux in weber\n", "l=math.pi*50*10**-2 #length in m\n", "A=10*10**-4 #area of cross-section\n", "N=1000 #number of turns\n", "i=5 #current in A\n", "muo=4*math.pi*10**-7\n", "#phi(magnetic flux)=m.m.f/reluctance\n", "#phi=N*i*muo*mur*A/l\n", "#we get,\n", "mur=phi*l/(N*i*A*muo)\n", "print \"relative permeability of the medium is mur=\",mur,\"unitless\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "relative permeability of the medium is mur= 375.0 unitless\n" ] } ], "prompt_number": 9 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex10.7:pg-295" ] }, { "cell_type": "code", "collapsed": false, "input": [ "import math\n", "#to calculate magnetising current\n", "#formula is phi(magnetic flux)=m.m.f/reluctance\n", "#phi=N*i*mu*A/l--------eq(1)\n", "#phi=BA------------eq(2)\n", "B=0.20 #magnetic flux density in weber/m**2\n", "l=1 #average length of the circuit in m \n", "N=100 #number of turns\n", "mu=7.3*10**-3 #in h.m\n", "#from eq(1)and eq(2),we get\n", "i=B*l/(N*mu)\n", "print \"magnetising current is i=\",round(i,3),\"A\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "magnetising current is i= 0.274 A\n" ] } ], "prompt_number": 10 } ], "metadata": {} } ] }