As of now, one of the Physics 8B lectures is full, but the other has 12 spaces open (though 11 of the open lab spaces are in W 4-6pm).
There are three Physics 7B lectures. One is full, one at (TuTh 8-9:30am) has 46 spaces open, and one has 9 spaces open (with most of the open lab spaces at Tu 8-10am or Th 8-10am). There is also a Physics H7B (honors course) with 21 open spaces (out of 25 total).
Physics 7B can substitute for Physics 8B, according to the MCB handbook
. However, this is generally considered to be the "harder" physics course for physics and engineering majors, and requires Math 53 (multivariable calculus) as at least a co-requisite.