Plot a vector field for differential equation?

Questions
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1

Hi i’m trying to plot a vector field for differential equation:

T(t)'=-1/50 (T[t]-20)

could you please tell me where i’m doing wrong.

VectorPlot[{t, -1/50 (y - 20)}, {t, -3, 3}, {y, -3, 3}]
2

The vector field of the equation T’(t)=-1/50 (T[t]-20) does not depend on t. The slope depends only on the y value. You get a vector of that slope for example with {1, - 1/50 (y - 20)}. Try with

VectorPlot[{1, - 1/50 (y - 20)}, {t, -3, 100}, {y, 0, 40}]

or, even better, with

StreamPlot[{1, - 1/50 (y - 20)}, {t, -3, 100}, {y, 0, 40}]
3

Thanks a lot Gianluca Gorni