function TPhysic.Potenz10(z: real; nr : Integer): String;
var help, hs : String;
    i,e,s,stellen : Integer;
    b : boolean;
begin
{ aufbau zB  0.000021 ergebnis :  2.1*10^-5
  nr = genauigkeit}
  help := floatToStr(z);
  s := 3;
  if nr > Length(help)-1 then nr := nr - Length(help)-1;
  hs := '';
  stellen := 0;
  b := false;
  if (help[1] = '0') and (help[2] = ',') then
  begin
    for i:= 3 to length(help)-1 do
    begin s := s + 1;
        if b = false then
      if help[i] <> '0' then
      begin
        b := true;
        hs := help[i] + ',';
        for e := s to length(help)-1 do
          hs := hs + help[e];
      end
      else
          inc(stellen);
    delete(hs,2+nr,length(hs)-(2+nr));
    result := hs + '*10^-' + IntToStr(Stellen+1)
    end;
  end
  else
  begin

  end;
end;