An inductor coil, comprising: - a first component; - a second component; - a length of conductor; - a heat sink; wherein, the first component is located adjacent to the second component; wherein, a core is formed from cylindrical portions of the first component and the second component; wherein, a first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor; wherein, the heat sink comprises a thermally conductive material; wherein, the heat sink comprises a first part (90, 110) and a second part; wherein, the first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic; and wherein, an inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor; wherein the first material and/or structural characteristic comprises a resistance or resistivity and the second material and/or structural characteristic comprises a resistance or resistivity less than the resistance or resistivity of the first part of the heat sink; and characterized in that a circumferential resistance of the first part of the heat sink is greater than a radial resistance of the first part of the heat sink, and wherein the circumferential resistance of the first part of the heat sink is greater than a radial resistance of the second part of the heat sink and is greater than a circumferential resistance of the second part of the heat sink. - a first component; - a second component; - a length of conductor; - a heat sink; wherein, the first component is located adjacent to the second component; wherein, a core is formed from cylindrical portions of the first component and the second component; wherein, a first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor; wherein, the heat sink comprises a thermally conductive material; wherein, the heat sink comprises a first part (90, 110) and a second part; wherein, the first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic; and wherein, an inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor; wherein the first material and/or structural characteristic comprises a resistance or resistivity and the second material and/or structural characteristic comprises a resistance or resistivity less than the resistance or resistivity of the first part of the heat sink; and characterized in that a circumferential resistance of the first part of the heat sink is greater than a radial resistance of the first part of the heat sink, and wherein the circumferential resistance of the first part of the heat sink is greater than a radial resistance of the second part of the heat sink and is greater than a circumferential resistance of the second part of the heat sink. wherein, the first component is located adjacent to the second component; wherein, a core is formed from cylindrical portions of the first component and the second component; wherein, a first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor; wherein, the heat sink comprises a thermally conductive material; wherein, the heat sink comprises a first part (90, 110) and a second part; wherein, the first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic; and wherein, an inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor; wherein the first material and/or structural characteristic comprises a resistance or resistivity and the second material and/or structural characteristic comprises a resistance or resistivity less than the resistance or resistivity of the first part of the heat sink; and characterized in that a circumferential resistance of the first part of the heat sink is greater than a radial resistance of the first part of the heat sink, and wherein the circumferential resistance of the first part of the heat sink is greater than a radial resistance of the second part of the heat sink and is greater than a circumferential resistance of the second part of the heat sink.