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fixed typo

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edited Jan 1, 2017 at 17:06

62.1k
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Actually, simply

p = First@NDSolve[{f''[x] == - Sum[z[i] cp[i], {i, 1, 2}], 
    f[10] == zf/(ep a^2), f'[20] == 0}, f, {x, 10, 100 }];
Plot[(f /. p)[x], {x, 10, 100 }]

gives the same answer. The term D[HeavisideTheta[x - 10], x] zf/(ep a^2) has no effect, because it is at the boundary. It is strange that NDSolve gives an error instead of just ignoring the term.

Actually, simply

p = First@NDSolve[{f''[x] == Sum[z[i] cp[i], {i, 1, 2}], 
    f[10] == zf/(ep a^2), f'[20] == 0}, f, {x, 10, 100 }];
Plot[(f /. p)[x], {x, 10, 100 }]

gives the same answer. The term D[HeavisideTheta[x - 10], x] zf/(ep a^2) has no effect, because it is at the boundary. It is strange that NDSolve gives an error instead of just ignoring the term.

Actually, simply

p = First@NDSolve[{f''[x] == - Sum[z[i] cp[i], {i, 1, 2}], 
    f[10] == zf/(ep a^2), f'[20] == 0}, f, {x, 10, 100 }];
Plot[(f /. p)[x], {x, 10, 100 }]

gives the same answer. The term D[HeavisideTheta[x - 10], x] zf/(ep a^2) has no effect, because it is at the boundary. It is strange that NDSolve gives an error instead of just ignoring the term.

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created Dec 31, 2016 at 17:10

bbgodfrey

62.1k
18
92
160

Actually, simply

p = First@NDSolve[{f''[x] == Sum[z[i] cp[i], {i, 1, 2}], 
    f[10] == zf/(ep a^2), f'[20] == 0}, f, {x, 10, 100 }];
Plot[(f /. p)[x], {x, 10, 100 }]

gives the same answer. The term D[HeavisideTheta[x - 10], x] zf/(ep a^2) has no effect, because it is at the boundary. It is strange that NDSolve gives an error instead of just ignoring the term.