In a purely inductive circuit, the current lags behind the voltage in phase by 90 degrees. This means that the maximum value of the current occurs after the maximum value of the voltage. In simpler terms, when the voltage is at its highest point, the current is still increasing and has not yet reached its highest point. This is because in an inductive circuit, the current is impeded by the inductor, which resists changes in current. As a result, the current takes some time to catch up to the voltage.