{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "

Chapter 24: Application of complex numbers to series a.c. circuits

" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 1, page no. 433

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine the values of the resistance and the series-connected inductance or capacitance for each of the following impedances:\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "z1 = 12 + 5j;\n", "z2 = -40j;\n", "r3 = 30;\n", "theta3 = 60;# in degrees\n", "r4 = 2.20E6; \n", "theta4 = -30;# in degrees\n", "f = 50;# in Hz\n", "\n", "#calculation:\n", " #for an R-L series circuit, impedance\n", " # Z = R + iXL\n", "Ra = z1.real\n", "XLa = z1.imag\n", "La = XLa/(2*math.pi*f)\n", " #for a purely capacitive circuit, impedance Z = -iXc\n", "Xcb = abs(z2.imag)\n", "Cb = 1/(2*math.pi*f*Xcb)\n", "z3 = r3*cmath.cos(theta3*math.pi/180) + (r3*cmath.sin(theta3*math.pi/180))*1j\n", "Rc = z3.real\n", "XLc = z3.imag\n", "Lc = XLc/(2*math.pi*f)\n", "z4 = r4*cmath.cos(theta4*math.pi/180) + (r4*cmath.sin(theta4*math.pi/180))*1j\n", "Rd = z4.real\n", "Xcd = abs(z4.imag)\n", "Cd = 1/(2*math.pi*f*Xcd)\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)an impedance (12 + i5)ohm represents a resistance of \",round( Ra,2),\" ohm \"\n", "print \"in series with an inductance of \",round(La*1000,2),\"mH\"\n", "print \"\\n (b)an impedance -40i ohm represents a pure capacitor of capacitance \",round(Cb*1E6,2),\"uF\"\n", "print \"\\n (c)an impedance 30/_60deg ohm represents a resistance of \",round(Rc,2),\" ohm \"\n", "print \"in series with an inductance of \",round(Lc*1000,2),\"mH\"\n", "print \"\\n (d)an impedance 2.20 x 10^6 /_-30deg ohm represents a resistance of \",round(Rd/1000,2),\"kohm \"\n", "print \" in series with a capacitor of capacitance \",round(Cd*1E9,2),\"nF\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)an impedance (12 + i5)ohm represents a resistance of 12.0 ohm \n", "in series with an inductance of 15.92 mH\n", "\n", " (b)an impedance -40i ohm represents a pure capacitor of capacitance 79.58 uF\n", "\n", " (c)an impedance 30/_60deg ohm represents a resistance of 15.0 ohm \n", "in series with an inductance of 82.7 mH\n", "\n", " (d)an impedance 2.20 x 10^6 /_-30deg ohm represents a resistance of 1905.26 kohm \n", " in series with a capacitor of capacitance 2.89 nF\n" ] } ], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 2, page no. 434

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine, in polar and rectangular forms, the current flowing in an inductor of negligible resistance and inductance\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "L = 0.1592 ;# in Henry\n", "V = 250;# in Volts\n", "f = 50;# in Hz\n", "R = 0;# in ohms\n", "\n", "#calculation:\n", " #for an R\u00e2\u20ac\u201cL series circuit, impedance\n", " # Z = R + iXL\n", "XL = 2*math.pi*f*L\n", "Z = R + 1j*XL\n", "I = V/Z\n", "x = I.real\n", "y = I.imag\n", "r = (x**2 + y**2)**0.5\n", "if ((x==0)&(y<0)):\n", " theta = -90\n", "elif ((x==0)&(y>0)):\n", " theta = +90\n", "else:\n", " theta = cmath.phase(complex(x,y))*180/math.pi\n", "\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n current is (\",round(r,2),\"/_\",theta,\"deg) A\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " current is ( 5.0 /_ -90 deg) A" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 3, page no. 435

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine the value of the supply p.d.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "C = 3E-6 ;# in farad\n", "f = 1000;# in Hz\n", "ri = 2.83;\n", "thetai = 90;# in degrees\n", "\n", "#calculation:\n", " #Capacitive reactance Xc\n", "Xc = 1/(2*math.pi*f*C)\n", " # circuit impedance Z\n", "Z = -1*1j*Xc\n", "I = ri*math.cos(thetai*math.pi/180) + 1j*ri*math.sin(thetai*math.pi/180)\n", "V = I*Z\n", "x = V.real\n", "y = V.imag\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n supply p.d. is \",round(abs(V),0),\"V\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " supply p.d. is 150.0 V" ] } ], "prompt_number": 3 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 4, page no. 435

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine (a) the resistance, (b) the capacitance, \n", "#(c) the modulus of the impedance, and (d) the current flowing and its phase angle,\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "V = 240;# in Volts\n", "f = 50;# in Hz\n", "Z = 30 - 50j;\n", "\n", "#calculation:\n", " #Since impedance Z = 30 - i50,\n", " #resistance\n", "R = Z.real\n", " #capacitive reactance\n", "Xc = abs(Z.imag)\n", " #capacitance\n", "C = 1/(2*math.pi*f*Xc)\n", " #modulus of impedance\n", "modZ = (R**2 + Xc**2)**0.5\n", "I = V/Z\n", "x = I.real\n", "y = I.imag\n", "r = (x**2 + y**2)**0.5\n", "theta = cmath.phase(complex(x,y))*180/math.pi\n", "\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)resistance is \",round( R,2),\" ohm\"\n", "print \"\\n (b)capacitance is \",round(C*1E6,2),\"uFarad\"\n", "print \"\\n (c)modulus of impedance is \",round(modZ,2),\" ohm\"\n", "print \"\\n (d)current flowing and its phase angle is (\",round( r,2),\"/_\",round( theta,2),\"deg) A\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)resistance is 30.0 ohm\n", "\n", " (b)capacitance is 63.66 uFarad\n", "\n", " (c)modulus of impedance is 58.31 ohm\n", "\n", " (d)current flowing and its phase angle is ( 4.12 /_ 59.04 deg) A" ] } ], "prompt_number": 4 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 5, page no. 436

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine (a) the impedance of the circuit,\n", "#(b) the current and circuit phase angle, \n", "#(c) the p.d. across the 32 ohm resistor, and (d) the p.d. across the coil\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "V = 200;# in Volts\n", "f = 50;# in Hz\n", "R = 32;# in ohms\n", "L = 0.15;# in Henry\n", "\n", "#calculation:\n", " #Inductive reactance XL\n", "XL = 2*math.pi*f*L\n", " #impedance, Z\n", "Z = R + 1j*XL\n", " #Current I\n", "I = V/Z\n", "xi = I.real\n", "yi = I.imag\n", "ri = (xi**2 + yi**2)**0.5\n", "if ((xi==0)&(yi<0)):\n", " thetai = -90\n", "elif ((xi==0)&(yi>0)):\n", " thetai = +90\n", "else:\n", " thetai = cmath.phase(complex(xi,yi))*180/math.pi\n", "\n", " #P.d. across the resistor\n", "VR = I*R\n", "xr = VR.real\n", "yr = VR.imag\n", "rr = (xr**2 + yr**2)**0.5\n", "thetar = cmath.phase(complex(xr,yr))*180/math.pi\n", " #P.d. across the coil, VL\n", "VL = I*1j*XL\n", "xl = VL.real\n", "yl = VL.imag\n", "rl = (xl**2 + yl**2)**0.5\n", "thetal = cmath.phase(complex(xl,yl))*180/math.pi\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)impedance is \",round(Z.real,2),\" + \",round( Z.imag,2),\")i ohm\"\n", "print \"\\n (b)current flowing and its phase angle is lagging the voltage = (\",round( ri,2),\"/_\",round( thetai,2),\"deg) A\"\n", "print \"\\n (c)P.d. across the resistor is (\",round(rr,2),\"/_\",round(thetar,2),\"deg) V\"\n", "print \"\\n (d)P.d. across the coil, VL is (\",round(rl,2),\"/_\",round(thetal,2),\"deg) V\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)impedance is 32.0 + 47.12 )i ohm\n", "\n", " (b)current flowing and its phase angle is lagging the voltage = ( 3.51 /_ -55.82 deg) A\n", "\n", " (c)P.d. across the resistor is ( 112.36 /_ -55.82 deg) V\n", "\n", " (d)P.d. across the coil, VL is ( 165.46 /_ 34.18 deg) V" ] } ], "prompt_number": 4 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 6, page no. 436

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine the value of impedance\n", "#determine the value of the components forming the series circuit.\n", "from __future__ import division\n", "import math\n", "#initializing the variables:\n", "V = 120 + 200j;# in Volts\n", "f = 5E6;# in Hz\n", "I = 7 + 16j;# in amperes\n", "\n", "#calculation:\n", " #impedance, Z\n", "Z = V/I\n", "R = Z.real\n", "X = Z.imag \n", "if ((R>0)&(X<0)):\n", " C = -1/(2*math.pi*f*X)\n", "#Results\n", " print \"\\n\\n Result \\n\\n\"\n", " print \"\\n The series circuit thus consists of a resistor of resistance \",round(R,2),\" ohm \"\n", " print \"and a capacitor of capacitive reactance\", round(X*-1,3),\"ohm and capacitance is\",round(C*1E9,2),\" nFarad\\n\"\n", "elif ((R>0)&(X>0)):\n", " L = 2*math.pi*f*X\n", "#Results\n", " print \"\\n\\n Result \\n\\n\"\n", " print \"\\n The series circuit thus consists of a resistor of resistance \",round(R,2),\" ohm \"\n", " print \" and a inductor of insuctance \",round(L*100,2),\" mHenry\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " The series circuit thus consists of a resistor of resistance 13.25 ohm \n", "and a capacitor of capacitive reactance 1.705 ohm and capacitance is 18.67 nFarad\n", "\n" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 7, page no. 437

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#determine the value of impedance Z2.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "rv = 70;# in volts\n", "thetav = 30;# in degrees\n", "ri = 3.5;# in amperes\n", "thetai = -20;# in degrees\n", " #z1 consist of two resistance\n", "R1 = 4.36;# in ohms\n", "R2 = -2.1j;# in ohms\n", "\n", " #calculation:\n", "V = rv*math.cos(thetav*math.pi/180) + 1j*rv*math.sin(thetav*math.pi/180)\n", "I = ri*math.cos(thetai*math.pi/180) + 1j*ri*math.sin(thetai*math.pi/180)\n", " #impedance, Z\n", "Z = V/I\n", " #Total impedance Z = z1 + z2\n", "Z1 = R1 + R2\n", "Z2 = Z - Z1\n", "x = Z2.real\n", "y = Z2.imag \n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n impedance Z2 is \",round(x,2),\" + (\",round(y,2),\")i ohm\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " impedance Z2 is 8.5 + ( 17.42 )i ohm" ] } ], "prompt_number": 9 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 8, page no. 437

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#determine (a) the supply voltage, (b) the voltage across the 90 \u000e resistance, \n", "#(c) the voltage across the inductance, and (d) the circuit phase angle.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "R = 90;# in ohms\n", "XL = 150;# in ohms\n", "ri = 1.35;# in amperes\n", "thetai = 0;# in degrees\n", "\n", "#calculation:\n", "I = ri*math.cos(thetai*math.pi/180) + 1j*ri*math.sin(thetai*math.pi/180)\n", " #Circuit impedance Z\n", "Z = R + 1j*XL\n", " #Supply voltage, V\n", "V = I*Z\n", " #Voltage across 90 ohm\u000e resistor\n", "VR = V.real\n", "#Voltage across inductance, VL\n", "VL = V.imag\n", "xv = V.real\n", "yv = V.imag\n", "rv = (xv**2 + yv**2)**0.5\n", "thetav = cmath.phase(complex(xv,yv))*180/math.pi\n", "phi = thetav - thetai\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)Supply voltage, V is \",xv,\" + (\",yv,\")i V\\n\"\n", "print \"\\n (b)Voltage across 90 ohm resistor, VR is \",VR,\" V\\n\"\n", "print \"\\n (c)Voltage across inductance, VL is \",VL,\" V\\n\"\n", "print \"\\n (d)Circuit phase angle is \",round(phi,2),\"deg lagging\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)Supply voltage, V is 121.5 + ( 202.5 )i V\n", "\n", "\n", " (b)Voltage across 90 ohm resistor, VR is 121.5 V\n", "\n", "\n", " (c)Voltage across inductance, VL is 202.5 V\n", "\n", "\n", " (d)Circuit phase angle is 59.04 deg lagging" ] } ], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 9, page no. 438

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine (a) the rms value of voltage (in polar form),\n", "#(b) the circuit impedance, (c) the rms current flowing, and\n", "#(d) the circuit phase angle.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "R = 25;# in ohms\n", "L = 0.02;# in henry\n", "Vm = 282.8;# in volts\n", "w = 628.4;# in rad/sec\n", "phiv = math.pi/3;# phase angle\n", "\n", "#calculation:\n", " #rms voltage\n", "Vrms = 0.707*Vm*math.cos(phiv) + 0.707*Vm*math.sin(phiv)*1j\n", " #frequency\n", "f = w/(2*math.pi)\n", " #Inductive reactance XL\n", "XL = 2*math.pi*f*L\n", " #Circuit impedance Z\n", "Z = R + XL*1j\n", " #Rms current\n", "Irms = Vrms/Z\n", "phii = cmath.phase(complex(Irms.real, Irms.imag))*180/math.pi\n", "phi = phiv*180/math.pi - phii\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)the rms value of voltage is \",round(Vrms.real,2),\" + (\",round( Vrms.imag,2),\")i V\\n\"\n", "print \"\\n (b)the circuit impedance is \",round(R,2),\" + (\",round( XL,2),\")i ohm\\n\"\n", "print \"\\n (c)the rms current flowing is \",round(Irms.real,2),\" + (\",round( Irms.imag,2),\")i A\\n\"\n", "print \"\\n (d)Circuit phase angle is \",round(phi,2),\"deg lagging\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)the rms value of voltage is 99.97 + ( 173.15 )i V\n", "\n", "\n", " (b)the circuit impedance is 25.0 + ( 12.57 )i ohm\n", "\n", "\n", " (c)the rms current flowing is 5.97 + ( 3.92 )i A\n", "\n", "\n", " (d)Circuit phase angle is 26.69 deg lagging\n" ] } ], "prompt_number": 5 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 10, page no. 438

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine the current flowing in the circuit\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "R = 12;# in ohms\n", "L = 0.10;# in henry\n", "C = 120E-6;# in Farads\n", "f = 50;# in Hz\n", "V = 240;# in volts\n", "\n", "#calculation:\n", " #Inductive reactance, XL\n", "XL = 2*math.pi*f*L\n", " #Capacitive reactance, Xc\n", "Xc = 1/(2*math.pi*f*C)\n", " #Circuit impedance Z\n", "Z = R + 1j*(XL - Xc)\n", "I = V/Z\n", "phii = cmath.phase(complex(I.real, I.imag))*180/math.pi\n", "phiv = 0# in degrees\n", "phi = phiv - phii\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n the current flowing is \",round(abs(I),1),\"/_\",round(cmath.phase(complex(I.real,I.imag))*180/math.pi,1),\"deg A\\n\"\n", "print \"and Circuit phase angle is \",round(phi,1),\"deg lagging\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " the current flowing is 18.5 /_ -22.2 deg A\n", "\n", "and Circuit phase angle is 22.2 deg lagging\n" ] } ], "prompt_number": 11 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 11, page no. 439

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#determine the values of R and L, Determine also the voltage across the coil and the voltage across the capacitor.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "C = 50E-6;# in Farads\n", "f = 50;# in Hz\n", "V = 225;# in volts\n", "ri = 1.5;# in Amperes\n", "thetai = -30;# in degrees\n", "\n", "#calculation:\n", "I = ri*math.cos(thetai*math.pi/180) + 1j*ri*math.sin(thetai*math.pi/180)\n", " #Capacitive reactance, Xc\n", "Xc = 1/(2*math.pi*f*C)\n", " #Circuit impedance Z\n", "Z = V/I\n", "R = Z.real\n", "XL = Z.imag + Xc\n", " #inductance L\n", "L = XL/(2*math.pi*f)\n", " #Voltage across coil\n", "Zcoil = R + 1j*XL\n", "Vcoil = I*Zcoil\n", " #Voltage across capacitor,\n", "Vc = I*(-1j*Xc)\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n (a)resistance is \",round(R,2),\" ohm and inductance is \",round( L,3),\" H\\n\"\n", "print \"\\n (b)voltage across the coil is \",round(Vcoil.real,2),\" + (\",round( Vcoil.imag,2),\")i V\\n\"\n", "print \"\\n (c)voltage across the capacitor is \",round(Vc.real,2),\" + (\",round( Vc.imag,2),\")i V\\n\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " (a)resistance is 129.9 ohm and inductance is 0.441 H\n", "\n", "\n", " (b)voltage across the coil is 272.75 + ( 82.7 )i V\n", "\n", "\n", " (c)voltage across the capacitor is -47.75 + ( -82.7 )i V" ] } ], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 12, page no. 440

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Determine also the value of the supply voltage V and the circuit phase angle.\n", "from __future__ import division\n", "import math\n", "import cmath\n", "#initializing the variables:\n", "C = 2.653E-6;# in Farads\n", "R1 = 8;# in ohms\n", "R2 = 5;# in ohms\n", "L = 0.477E-3;# in Henry\n", "f = 4000;# in Hz\n", "ri = 6;# in Amperes\n", "thetai = 0;# in degrees\n", "\n", "#calculation:\n", "I = ri*math.cos(thetai*math.pi/180) + 1j*ri*math.sin(thetai*math.pi/180)\n", " #Capacitive reactance, Xc\n", "Xc = 1/(2*math.pi*f*C)\n", " #impedance Z1\n", "Z1 = R1 - 1j*Xc\n", " #inductive reactance XL\n", "XL = 2*math.pi*f*L\n", " #impedance Z2,\n", "Z2 = R2 + 1j*XL\n", " #voltage V1\n", "V1 = I*Z1\n", " #voltage V2\n", "V2 = I*Z2\n", " #Supply voltage, V\n", "V = V1 + V2\n", "phiv = cmath.phase(complex(V.real, V.imag))*180/math.pi\n", "phi = phiv - thetai\n", "\n", "\n", "#Results\n", "print \"\\n\\n Result \\n\\n\"\n", "print \"\\n supply voltage is \",round(V.real,2),\" + (\",round( V.imag,2),\")i V\\n\"\n", "print \"and Circuit phase angle is \",round(phi,2),\"deg leading\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", "\n", " Result \n", "\n", "\n", "\n", " supply voltage is 78.0 + ( -18.06 )i V\n", "\n", "and Circuit phase angle is -13.03 deg leading" ] } ], "prompt_number": 2 } ], "metadata": {} } ] }