V[x_,y_]=Sum[4* 1/(m Pi) E^(-m Pi x/1) Sin[m Pi y/1],{m,1,25,2}]

Plot3D[V[x,y],{x,0,4},{y,0,1},PlotRange->All]

Plot[V[x,0.5],{x,0,4},PlotRange->All]

Plot[V[x,0.05],{x,0,4},PlotRange->All]

Plot3D[V[x,y],{x,0,4},{y,0,1},PlotRange->All,ViewPoint->{-2,-2,1}]

Plot3D[V[x,y],{x,0,4},{y,0,1},PlotRange->All,ViewPoint->{0,0,1.5}]