Current source with low-side LOAD
Start by assuming you have an ideal opamp.  The second circuit is going to try to pull the non-inverting input down to +5V.  This requires that 5A flows through the 1-Ohm R2 (a 10V supply, a 5V drop across R2).  However, this same current would also have to flow through the 100 Ohm load, which is not possible with the 10V supply (5A * 100 Ohm = 500V).

The circuit would work if you replaced the +5V reference with one much closer to +10V.