An electric machine with at least one electrical resistor (24) for dissipating shaft voltages occurring at the rotor shaft (2) of a rotor (1), in which the electrical resistor (24) is enclosed in a contact ring (13) mounted on the rotor shaft (2) between contact surfaces (17, 23, 25, 28, 29) applied to the contact ring (13) on the outside, and in which the resistor (24) is electrically connected via the contact surfaces (17, 23, 25, 28, 29) to the rotor shaft (2) on one side and to the excitation winding (14) of the rotor (1) on the other side.