Hello, I have been performing an experiment in which I am observing the lifting capacity of DC electromagnets while changing variables including current, number of turns, and length of the core. It is a fairly basic experiment as all the theoretical values can be obtained using the formula F=N2I2μ2A/2μ0L2 However I am getting results that do not satisfy this equation and I am not sure why this may be. Testing an electromagnet with a carbon steel core of length 6.5cm and 77 turns in the solenoid with currents of 5.04 A , 3.77 A and, 2.51 A I get average maximum lifting mass results of 0.7447 kg, 0.4179 kg, and 0.1875 kg respectively. However when I test the magnet with a core length of 12.25cm, 154 turns and the same currents, (which according to the theory should yield results of 1.126 times that of the first magnet) I get the following results of 1.7027 kg, 0.8407 kg, and 0.4036 kg respectively. The results of the second magnet are approximately two times greater than they should be according to the first magnet and the theory. Could it be that I am missing something obvious, and if so what? Any input would be valued.