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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Chapter 2 : Electric Circuits"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 1 : pg 6"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current in resistance Ra=1.0 ohm is ,(A)= 0.105\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.1 :current\n",
+    "#calculate the current \n",
+    "# given :\n",
+    "import numpy\n",
+    "#15*I1-5*I2=10 loop 1 equation\n",
+    "#20*I2-5*I1-5*I3=0 loop 2 equation\n",
+    "#10*I3-5*I2=0 loop 3 equation\n",
+    "vs=10.;#voltage in volts\n",
+    "R1=10.;#resistance in ohm\n",
+    "R2=5.;#resistance in ohm\n",
+    "R3=10.;#resistance in ohm\n",
+    "R4=5.;#resistance in ohm\n",
+    "R5=4.;#resistance in ohm\n",
+    "Ra=1.;#resistance in ohm\n",
+    "#calculations\n",
+    "A=([[R1+R2, R2-R1, 0],[R2-R1, R2+R3+R4, -R4],[R4-(R5+Ra), -R4, R4+R5+Ra]]);#making equations\n",
+    "nb=7.;#number of branches\n",
+    "nn=5.;#number of nodes\n",
+    "nl=nb-(nn-1);#number of loops\n",
+    "nvs=1.;#number of voltage sources\n",
+    "nivs=nn-1-nvs;#number of independent voltage variables\n",
+    "B=([[vs],[0],[0]]);#making equations\n",
+    "X=numpy.dot(numpy.linalg.inv(A),B);#solving equations\n",
+    "I3=X[2,0];#calculating currrent\n",
+    "#results\n",
+    "print \"current in resistance Ra=1.0 ohm is ,(A)=\",round(I3,3)\n",
+    "#directions of the current are 2 to 3 and 3 to 4 respectively\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 2 : pg 6"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current through Rx is(by node voltage method), (A)= 3.956\n",
+      "current through Rx is (by loop current method),(A) = 3.956\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.2 :current\n",
+    "#calculate the current in both cases\n",
+    "import numpy\n",
+    "# given :\n",
+    "vs1=72.;#voltage in volts\n",
+    "vs2=40.;#voltage in volts\n",
+    "R1=36.;#resistance in ohm\n",
+    "R2=10.;#resistance in ohm\n",
+    "ig=2.;#current in amperes\n",
+    "Rx=8.;#resistance in ohm\n",
+    "#calculations\n",
+    "#(va-72)/36+(va-40)/10 -2 +va/8=0 node equation at 1\n",
+    "va=((R2*Rx*vs1)+(R1*Rx*vs2)+(R1*R2*Rx*ig))/((R2*Rx)+(R1*Rx)+(R1*R2));#voltage in volts\n",
+    "ix1=va/Rx;#current in amperes\n",
+    "#(R1+R2)*I1-R2*I2+vs2=vs1 loop equation 1\n",
+    "#R2*I2-R2*I1+Ix*Rx=vs2 loop equation 2\n",
+    "#Ix=I2+2\n",
+    "A=([[R1+R2, -R2],[-R2, R2+Rx]]);#making equations\n",
+    "B=([[vs1-vs2],[vs2-2*Rx]]);#making equations\n",
+    "X=numpy.dot(numpy.linalg.inv(A),B);#solving equations\n",
+    "ix2=X[1,0]+ig;#current in amperes\n",
+    "print \"current through Rx is(by node voltage method), (A)=\",round(ix1,3)\n",
+    "print \"current through Rx is (by loop current method),(A) =\",round(ix2,3)\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 3 : pg 7"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current through Rl is (from b to a),(A)= 0.359\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.3 :current\n",
+    "#calculate the current\n",
+    "import numpy\n",
+    "# given :\n",
+    "vs1=10;#voltage in volts\n",
+    "i5=2;#current in amperes\n",
+    "i2=i5;#current\n",
+    "r1=1;#resistance in ohms\n",
+    "r2=5;#resistance in ohms\n",
+    "r3=5;#resistance in ohms\n",
+    "rl=10;#resistance in ohms\n",
+    "r4=5;#resistance ohms\n",
+    "#calculations\n",
+    "#(r1+r2+r3)*i1-r2*i2-r3*i3=vs1 loop equaion 1\n",
+    "#-r2*i1-(r1+r2)*i2+(rl+r2+r3)*i3=0 loop equation 2\n",
+    "A=([[4*(r1+r2+r3), -r2*4],[-r2, (rl+r2+r3)]]);#making equations\n",
+    "B=([[4*(vs1+r2*i2)],[i2*(r2+r3)]]);#making equations\n",
+    "X=numpy.dot(numpy.linalg.inv(A),B);#solving equations\n",
+    "il=i2-X[1,0];#calculating current\n",
+    "#results\n",
+    "print \"current through Rl is (from b to a),(A)=\",round(il,3)\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 4 : pg 8"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Applying Thevenins Theorem \n",
+      "current through Rx is, (A) 3.956\n",
+      "Applying Nortons Theorem \n",
+      "current through Rx is, (A) = 3.956\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.4 :current\n",
+    "#calculate the current\n",
+    "# given :\n",
+    "vs1=72.;#voltage in volts\n",
+    "vs2=40.;#voltage in volts\n",
+    "R1=36.;#resistance in ohms\n",
+    "R2=10.;#resistance in ohms\n",
+    "ig=2.;#current in amperes\n",
+    "Rx=8.;#resistance in ohms\n",
+    "#calculations and results\n",
+    "print \"Applying Thevenins Theorem \"\n",
+    "#(vs1-voc)/R1+(v40-voc)/R2 +2 =0 node equation at 1\n",
+    "voc=(R2*vs1+R1*vs2+R1*R2*ig)/(R1+R2);#voltage in volts\n",
+    "req=(R1*R2)/(R1+R2);#resistance in ohms\n",
+    "ix1=(voc)/(req+Rx);#resistance in ohms\n",
+    "print \"current through Rx is, (A)\",round(ix1,3)\n",
+    "print \"Applying Nortons Theorem \"\n",
+    "Is=(vs1/R1)+(vs2/R2)+ig;#current in amperes\n",
+    "ix2=(req*(Is/(Rx+req)));#current in amperes\n",
+    "print \"current through Rx is, (A) =\",round(ix2,3)\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 5 : pg 8"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "(a) Applying Thevenins Theorem \n",
+      "Thevenin equivalent open circuit voltage is, (V)= 5.0\n",
+      "Thevenin equivalent resistance is,(Ohm)= 50.0\n",
+      "(b) Applying Nortons Theorem \n",
+      "Norton short circuit current is,(A)= 0.1\n",
+      "Norton equivalent resistance is,(Ohm)= 50.0\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.5 :Thevenin's and Norton's Equivalent\n",
+    "#calculate the current in all cases\n",
+    "# given :\n",
+    "vs1=10.;#voltage in volts\n",
+    "R1=50.;#resistance in ohms\n",
+    "R2=50.;#resistance in ohms\n",
+    "R3=25.;#resistance in ohms\n",
+    "#calculations and results\n",
+    "print \"(a) Applying Thevenins Theorem \"\n",
+    "voc=(R1/(R1+R2))*vs1;#voltage in volts\n",
+    "req=((R1*R2)/(R1+R2))+R3;#resistance in ohms\n",
+    "print \"Thevenin equivalent open circuit voltage is, (V)=\",voc\n",
+    "print \"Thevenin equivalent resistance is,(Ohm)=\",req\n",
+    "print \"(b) Applying Nortons Theorem \"\n",
+    "Isc=((vs1)/(R1+(R1*R3)/(R1+R3)))*(R1/(R1+R3));#\n",
+    "req=((R1*R2)/(R1+R2))+R3;#resistance in ohms\n",
+    "print \"Norton short circuit current is,(A)=\",Isc\n",
+    "print \"Norton equivalent resistance is,(Ohm)=\",req\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 6 : pg 10"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current through Rx is (from A to B),(mA)= 0.299\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.6 :current\n",
+    "#calculate the current \n",
+    "# given :\n",
+    "vs1=10.;#voltage volts\n",
+    "r1=100.;#resistance in ohms\n",
+    "r2=600.;#resistance in ohms\n",
+    "r3=150.;#resistance in ohms\n",
+    "r4=850.;#resistance in ohms\n",
+    "rx=50.;#resistance in ohms\n",
+    "#calculations\n",
+    "voc=vs1*((r3/(r1+r3))-(r4/(r2+r4)));#open circuit voltage in volts\n",
+    "req=((r1*r3)/(r1+r3))+((r2*r4)/(r2+r4));#equivalent resistance in ohms\n",
+    "ix=voc/(req+rx)*10**3;#current in amperes\n",
+    "#results\n",
+    "print \"current through Rx is (from A to B),(mA)=\",round(ix,3)\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 7 : pg 11"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current is,(A) -1.429\n",
+      "equivalent resistance is,(ohm)= 1.273\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.7 :\n",
+    "#calculate the Norton's Equivalent\n",
+    "# given :\n",
+    "vs1=40.;#volts\n",
+    "vs2=20.;#volts\n",
+    "r1=2.;#resistance in ohms\n",
+    "r2=6.;#resistance in ohms\n",
+    "r3=2.;#resistance in ohms\n",
+    "r4=2.;#resistance in ohms\n",
+    "#calculations\n",
+    "iab=((r1*vs1)/(r2+(r1/2))*((r1+(r3/2))/(r1+r3)));#current in amperes\n",
+    "iab1=-vs2/r1;#current amperes\n",
+    "it=iab+iab1;#current amperes\n",
+    "req1=r1+((r1*r2)/(r1+r2));#equivalent resistance in ohms\n",
+    "req=(req1*r3)/(req1+r3);#equivalent resistance in ohms\n",
+    "#results\n",
+    "print \"current is,(A)\",round(it,3)\n",
+    "print \"equivalent resistance is,(ohm)=\",round(req,3)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 8 : pg 12"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "current is (when t=500 micro seconds),(A)= 0.221\n",
+      "time at which current will be zero is,(micro-seconds)= 1222.0\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.8:equation of current and time\n",
+    "#calculate the current \n",
+    "from math import exp,ceil\n",
+    "# given :\n",
+    "v=100.;#voltage in volts\n",
+    "r=100.;#resistance in ohms\n",
+    "l=0.2;#inductance in henrty\n",
+    "#calculations and results\n",
+    "T=1/(l/r);#calculating time in seconds\n",
+    "t=500.;#time in micro seconds\n",
+    "i1=1-exp(-T*t*10**-6);#current in amperes\n",
+    "print \"current is (when t=500 micro seconds),(A)=\",round(i1,3)\n",
+    "v2=50.;#voltage in volts\n",
+    "x=v2/r;#variable\n",
+    "x1=x*((v2/r)+i1);#variable \n",
+    "t1=t+(10**6*(x1/500.));#time in seconds\n",
+    "print \"time at which current will be zero is,(micro-seconds)=\",ceil(t1)\n",
+    "#time is caluclated wrong in the textbook as they had not added the values\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 9 : pg 15"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 11,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "time is ,(seconds)= 0.025\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.9 :time\n",
+    "#calculate the time required\n",
+    "from math import log\n",
+    "# given :\n",
+    "v=10.;#voltage in volts\n",
+    "r1=500.;#resistance in ohms\n",
+    "ix=0.;#current in amperes\n",
+    "r=700;#resistance in ohms\n",
+    "c=100;#capacitance in micro farads\n",
+    "#calculations\n",
+    "x=1/(r*c*10**-6);#variable\n",
+    "i=30;#current in mA\n",
+    "y=(i*10**-3)-(v/r1);#variable\n",
+    "t=-((log(y*(r/v))));#time in seconds\n",
+    "t1=t/x;#time in seconds\n",
+    "#results\n",
+    "print \"time is ,(seconds)=\",round(t1,3)\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 10 : pg 18"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 12,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "it=  2.697 *e^ -250.0 t*sin 370.81 t A\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.10 :current equation\n",
+    "#calculate the current equation\n",
+    "# given :\n",
+    "from numpy import roots\n",
+    "v=100.;#volts\n",
+    "r=50.;#in ohms\n",
+    "l=0.1;#henry\n",
+    "c=50.;#mf\n",
+    "#calculations\n",
+    "p = ([1,500.0,2*10**5])\n",
+    "#p=2*10**5+500*d+d**2;\n",
+    "x=roots(p)\n",
+    "c1=0;#at t=0 i=0\n",
+    "c2=1000/x[0].imag;#\n",
+    "#results\n",
+    "print \"it= \",round(c2,3),\"*e^\",x[0].real,\"t*sin\",round(x[0].imag,3),\"t A\"\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 11 : pg 19"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "parts (a) saw tooth wave\n",
+      "rms value of e is ,(V)= 0.886\n",
+      "average value of e is ,(V)= 5\n",
+      "parts (b) half wave rectified sine wave form\n",
+      "rms value of e is ,(V)= 5.0\n",
+      "average value of e is ,(V)= 3.183\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.11 :\n",
+    "#calculate the average & rms value\n",
+    "# given :\n",
+    "from numpy import linspace\n",
+    "from math import sin,pi,sqrt\n",
+    "from scipy import integrate\n",
+    "vm=10;#voltage in volts\n",
+    "e=vm/2;#voltage in volts\n",
+    "t=linspace(0,2, num=3);#time range\n",
+    "#x=intsplin(t,(5*t)**2);#variable\n",
+    "x=1.571;\n",
+    "#calculations and results\n",
+    "rms=sqrt(x/2);#rms value of voltage in volts\n",
+    "av=vm/2;#average value of voltage in volts\n",
+    "print \"parts (a) saw tooth wave\"\n",
+    "print \"rms value of e is ,(V)=\",round(rms,3)\n",
+    "print \"average value of e is ,(V)=\",av\n",
+    "t1=0;#initial time in seconds\n",
+    "t2=pi;#final time in seconds\n",
+    "t3=2*pi;#time interval\n",
+    "def function(t):\n",
+    "    return sin(t) *sin(t);\n",
+    "\n",
+    "def function2(t):\n",
+    "    return sin(t)\n",
+    "    \n",
+    "x=integrate.quad(function,t1,t2)[0];#variable\n",
+    "rms=sqrt((1/(2*pi))*x*vm**2);#rms value of voltage in volts\n",
+    "av=(10/(2*pi))*integrate.quad(function2,t1,t2)[0];#average value of voltage in volts\n",
+    "print \"parts (b) half wave rectified sine wave form\"\n",
+    "print \"rms value of e is ,(V)=\",rms\n",
+    "print \"average value of e is ,(V)=\",round(av,3)\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 12 : pg 20"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "part (a)\n",
+      "Impedance is ,(Ohm)= (16.4700606969+2.90411607477j)\n",
+      "part (b)\n",
+      "Impedance is ,(Ohm)= (3.53553390593+3.53553390593j)\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.12 :\n",
+    "#calculate the Circuit constants\n",
+    "# given :\n",
+    "from math import sqrt, cos, sin,pi\n",
+    "#v=194*cos(800*t+150)V Voltage equation\n",
+    "#I=11.6*cos(800*t+140)A Current equation\n",
+    "vm=194/sqrt(2);#voltage in volts\n",
+    "va=150;#angle in degree\n",
+    "im=11.6/sqrt(2);#current in amperes\n",
+    "ia=140;#angle in degree\n",
+    "#calculations and results\n",
+    "zm=vm/im;#resistance in ohms\n",
+    "za=va-ia;#resistance in ohms\n",
+    "z1=zm*cos(za*pi/180.);#reactance in ohms\n",
+    "z2=zm*sin(za*pi/180.);#reactance in ohms\n",
+    "z=z1+1j*z2;#resistance in ohms\n",
+    "print \"part (a)\"\n",
+    "print \"Impedance is ,(Ohm)=\",z\n",
+    "print \"part (b)\"\n",
+    "#v=6*sin(1000*t+45)V  Voltage equation\n",
+    "#I=12*cos(1000t-90)A current equation\n",
+    "vm1=60/sqrt(2);#voltage in volts\n",
+    "va1=45;#angle in degree\n",
+    "im1=12/sqrt(2);#current in amperes\n",
+    "ia1=0;#angle in degree\n",
+    "zm1=vm1/im1;#resistance in ohms\n",
+    "za1=va1-ia1;#resistance in ohms\n",
+    "z11=zm1*cos(za1*pi/180.);#reactance in ohms\n",
+    "z21=zm1*sin(za1*pi/180.);#reactance in ohms\n",
+    "z22=z11+1j*z21;#impedance in ohms\n",
+    "print \"Impedance is ,(Ohm)=\",z22\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 13 : pg 22"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "reading V2 is,(V) 207.123\n",
+      "reading V4 is  507.123  V or  92.877  V\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.13 :reading\n",
+    "#calculate the voltage reading\n",
+    "# given :\n",
+    "from math import sqrt\n",
+    "v1=230.;#voltage in volts\n",
+    "v2=100.;#voltage in volts\n",
+    "#calculations\n",
+    "v2=sqrt(v1**2-v2**2);#voltage in volts\n",
+    "v3=300.;#voltage in volts\n",
+    "#results\n",
+    "print \"reading V2 is,(V)\",round(v2,3)\n",
+    "print \"reading V4 is \",round(v3+v2,3),\" V or \",round(v3-v2,3),\" V\"\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 14 : pg 25"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Impedance is ,(Ohm)= (14.1877554161-14.1877554161j)\n",
+      "capacitance is ,(micro-farads)= 28.1933250377\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.14 :circuit elements\n",
+    "#calculate the circuit elements\n",
+    "# given :\n",
+    "from math import sqrt,cos,sin,pi\n",
+    "#v=311*sin(2500*t+170) V voltage equation\n",
+    "#I=15.5*sin(2500*t-145)A current equation\n",
+    "vm=311/sqrt(2);#voltage in volts\n",
+    "va=170.;#angle in degree\n",
+    "im=15.5/sqrt(2);#current in amperes\n",
+    "ia=-145.;#angle in degree\n",
+    "#calculations\n",
+    "zm=vm/im;#resistance in ohms\n",
+    "za=(va-ia)-360.;#resistance ohms\n",
+    "z1=zm*cos(za*pi/180.);#resistance in ohms\n",
+    "z2=zm*sin(za*pi/180.);#resistance in ohms\n",
+    "z=z1+1j*z2;#resistance in ohms\n",
+    "t=2500;#time in seconds\n",
+    "c=(1/(z.real*t));#capacitance in farads\n",
+    "#results\n",
+    "print \"Impedance is ,(Ohm)=\",z\n",
+    "print \"capacitance is ,(micro-farads)=\",c*10**6\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 15 : pg 26"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 17,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "part (a) Star\n",
+      "phase voltage,(V)= 231.0\n",
+      "phase current,(A)= 5.0\n",
+      "line voltage ,(V)= 400\n",
+      "line current,(A)= 4.619\n",
+      "power ,(W)= 2560.0\n",
+      "part (b) Delta\n",
+      "phase voltage,(V)= 400.0\n",
+      "phase current,(A)= 8.0\n",
+      "line voltage ,(V)= 400.0\n",
+      "line current,(A)= 13.856\n",
+      "power ,(W)= 7680.0\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Example 2.15 :parameters\n",
+    "#calculate the parameters of phase, line voltage and current, power\n",
+    "from math import sqrt\n",
+    "# given :\n",
+    "z=40+1j*30;#resistance in ohms\n",
+    "zph=sqrt(z.real**2+z.imag**2);#resistance in ohms\n",
+    "pf=z.real/zph;#power factor\n",
+    "v=400;#voltage in volts\n",
+    "#calculations and results\n",
+    "vp=v/(sqrt(3));#voltage in volts\n",
+    "pc=vp/zph;#current in amperes\n",
+    "lv=v;#voltage in volts\n",
+    "lc=pc;#current om amperes\n",
+    "p=sqrt(3)*v*lc*pf;#power in watts\n",
+    "print \"part (a) Star\"\n",
+    "print \"phase voltage,(V)=\",round(vp)\n",
+    "print \"phase current,(A)=\",round(pc)\n",
+    "print \"line voltage ,(V)=\",lv\n",
+    "print \"line current,(A)=\",round(lc,3)\n",
+    "print \"power ,(W)=\",p\n",
+    "z1=40+1j*30;#ohms\n",
+    "zph1=sqrt(z1.real**2+z1.imag**2);#ohms\n",
+    "pf1=z1.real/zph1;#power factor\n",
+    "v1=400.;#volts\n",
+    "vp1=v1;#volts\n",
+    "pc1=vp1/zph1;#amperes\n",
+    "lv1=v1;#volts\n",
+    "lc1=pc1*sqrt(3);#amperes\n",
+    "p1=sqrt(3)*v1*lc1*pf1;#watts\n",
+    "print \"part (b) Delta\"\n",
+    "print \"phase voltage,(V)=\",round(vp1)\n",
+    "print \"phase current,(A)=\",round(pc1)\n",
+    "print \"line voltage ,(V)=\",lv1\n",
+    "print \"line current,(A)=\",round(lc1,3)\n",
+    "print \"power ,(W)=\",p1\n"
+   ]
+  }
+ ],
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+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
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