A power-transmitter-unit comprising: a power-transmitting-coil for wirelessly providing power to a power-receiver-unit, and a resonant-capacitor connected to the power-transmitting-coil, such that together they define an LC circuit, wherein the LC circuit comprises a first-end and a second-end; a controller configured to define a power-transmission-mode of operation for wirelessly providing power to the power-receiver-unit and a foreign-object-detection-mode of operation, wherein: in the foreign-object-detection-mode of operation: the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit; and the controller is configured to receive a coil-current-signal that is representative of the current through the closed-LC-circuit; wherein the controller is further configured to: process the coil-current-signal that was received during the foreign-object-detection-mode of operation, in order to determine the resistance of the closed-LC-circuit, wherein the controller is configured to apply an auto-regressive modelling algorithm to the coil-current-signal in order to determine the resistance of the closed-LC-circuit; and provide an indication that a foreign object has been detected if the determined resistance of the closed-LC-circuit is greater than a resistance-threshold value; and wherein the controller is configured to: put the power-transmitter-unit into the foreign-object-detection-mode of operation after a first power-transmission-mode of operation; and put the power-transmitter-unit into a second power-transmission-mode of operation after the foreign-object-detection-mode of operation, if the foreign-object-detection-mode of operation provides an indication that a foreign object has not been detected. a power-transmitting-coil for wirelessly providing power to a power-receiver-unit, and a resonant-capacitor connected to the power-transmitting-coil, such that together they define an LC circuit, wherein the LC circuit comprises a first-end and a second-end; a controller configured to define a power-transmission-mode of operation for wirelessly providing power to the power-receiver-unit and a foreign-object-detection-mode of operation, wherein: in the foreign-object-detection-mode of operation: the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit; and the controller is configured to receive a coil-current-signal that is representative of the current through the closed-LC-circuit; the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit; and the controller is configured to receive a coil-current-signal that is representative of the current through the closed-LC-circuit; wherein the controller is further configured to: process the coil-current-signal that was received during the foreign-object-detection-mode of operation, in order to determine the resistance of the closed-LC-circuit, wherein the controller is configured to apply an auto-regressive modelling algorithm to the coil-current-signal in order to determine the resistance of the closed-LC-circuit; and provide an indication that a foreign object has been detected if the determined resistance of the closed-LC-circuit is greater than a resistance-threshold value; and process the coil-current-signal that was received during the foreign-object-detection-mode of operation, in order to determine the resistance of the closed-LC-circuit, wherein the controller is configured to apply an auto-regressive modelling algorithm to the coil-current-signal in order to determine the resistance of the closed-LC-circuit; and provide an indication that a foreign object has been detected if the determined resistance of the closed-LC-circuit is greater than a resistance-threshold value; and wherein the controller is configured to: put the power-transmitter-unit into the foreign-object-detection-mode of operation after a first power-transmission-mode of operation; and put the power-transmitter-unit into a second power-transmission-mode of operation after the foreign-object-detection-mode of operation, if the foreign-object-detection-mode of operation provides an indication that a foreign object has not been detected. put the power-transmitter-unit into the foreign-object-detection-mode of operation after a first power-transmission-mode of operation; and put the power-transmitter-unit into a second power-transmission-mode of operation after the foreign-object-detection-mode of operation, if the foreign-object-detection-mode of operation provides an indication that a foreign object has not been detected.