Electric rotary machine having a slip-ring arrangement, having a rotor, a sliding-contact device which is arranged on the rotor and has a slip ring and a sliding-contact element with which the slip ring can make electrical contact, a radial impeller wheel which is arranged on the rotor and has an intake device, wherein the intake device is embodied in such a way that during the operation of the radial impeller wheel a cooling fluid, which can be expelled, can be drawn into the radial impeller wheel by the intake device along the sliding-contact device, and a spiral housing which is of spiral design and surrounds a radial circumference of the radial impeller wheel, wherein the spiral housing has a spiral region and an outflow region which is arranged downstream of the spiral region and has an outflow opening, wherein in the spiral region an inner wall of the spiral housing is spaced apart from a rotational axis of the rotor in a way corresponding essentially to a spiral function, wherein in a junction region between the spiral region and the outflow region a tongue is formed by the inner wall in such a way that on the tongue, in a sectional plane perpendicular to the rotational axis, there is a tongue gap between the inner wall and an outer circumference of the radial impeller wheel, which tongue gap is the minimum distance between the inner wall and the outer circumference of the radial impeller wheel, wherein in the spiral region a maximum value of a distance between the outer circumference of the radial impeller wheel and the inner wall, said distance being measured proceeding radially from the rotational axis of the rotor, corresponds to six times to eight times the tongue gap, characterized in that the tongue is dull angled. having a rotor, a sliding-contact device which is arranged on the rotor and has a slip ring and a sliding-contact element with which the slip ring can make electrical contact, a radial impeller wheel which is arranged on the rotor and has an intake device, wherein the intake device is embodied in such a way that during the operation of the radial impeller wheel a cooling fluid, which can be expelled, can be drawn into the radial impeller wheel by the intake device along the sliding-contact device, and a spiral housing which is of spiral design and surrounds a radial circumference of the radial impeller wheel, wherein the spiral housing has a spiral region and an outflow region which is arranged downstream of the spiral region and has an outflow opening, wherein in the spiral region an inner wall of the spiral housing is spaced apart from a rotational axis of the rotor in a way corresponding essentially to a spiral function, wherein in a junction region between the spiral region and the outflow region a tongue is formed by the inner wall in such a way that on the tongue, in a sectional plane perpendicular to the rotational axis, there is a tongue gap between the inner wall and an outer circumference of the radial impeller wheel, which tongue gap is the minimum distance between the inner wall and the outer circumference of the radial impeller wheel, wherein in the spiral region a maximum value of a distance between the outer circumference of the radial impeller wheel and the inner wall, said distance being measured proceeding radially from the rotational axis of the rotor, corresponds to six times to eight times the tongue gap, characterized in that the tongue is dull angled.