However, there is at least one experiment in which value of the E and B are both zero at the location of a charged particle, but it is nevertheless affected by the presence of a local magnetic vector potential; see the Aharonov–Bohm effect for details. Nevertheless, even in the Aharonov–Bohm experiment, the divergence A never enters the calculations; only ∇ ∇ × × A along the path of the particle determines the measurable effect.