  A recent study demonstrated that freedom of convection and strength of
magnetic field in the photospheric feet of active-region (AR) coronal loops,
together, can engender or quench heating in them. Other studies stress that
magnetic flux cancellation at the loop-feet potentially drives heating in
loops. We follow 24-hour movies of a bipolar AR, using EUV images from SDO/AIA
and line-of-sight (LOS) magnetograms from SDO/HMI, to examine magnetic
polarities at the feet of 23 of the brightest coronal loops. We derived FeXVIII
emission (hot-94) images (using the Warren et al. method) to select the
hottest/brightest loops, and confirm their footpoint locations via
non-force-free field extrapolations. From 6"$\times$6" boxes centered at each
loop foot in LOS magnetograms we find that $\sim$40\% of the loops have both
feet in unipolar flux, and $\sim$60\% of the loops have at least one foot in
mixed-polarity flux. The loops with both feet unipolar are $\sim$15\% shorter
lived on average than the loops having mixed-polarity foot-point flux, but
their peak-intensity averages are equal. The presence of mixed-polarity
magnetic flux in at least one foot of majority of the loops suggests that flux
cancellation at the footpoints may drive most of the heating. But, the absence
of mixed-polarity magnetic flux (to the detection limit of HMI) in $\sim$40\%
of the loops suggests that flux cancellation may not be necessary to drive
heating in coronal loops -- magnetoconvection and field strength at both loop
feet possibly drive much of the heating, even in the cases where a loop foot
presents mixed-polarity magnetic flux.
