Transducer for obtaining electrical energy in a rolling wheel of a vehicle from the deformation of the wheel tyre by contact with the roadway, comprising a) at least one lever element which is rotatably mounted at its first end and at its second end is configured to come into contact with the inside of a wheel tyre via at least one contact element in such a way that a deformation of the wheel tyre due to contact with the roadway causes a rotational movement of the lever element, b) a mechanical coupling element, which is suitable for transmitting the force generated by the rotational movement of the lever element, and c) at least one electrical generator configured to convert the transmitted power into electrical energy, wherein at the second end of the lever element the contact element is rotatably mounted on the lever element about a rotational axis in such a way that the contact element facilitates the contact of the lever element with the wheel tyre, and the rotational axis of the contact element runs substantially parallel to the rotational axis of the wheel, characterised in that the ratio of the distance A of the axis of rotation of the lever element N from the wheel centre M to the radius of the inside of the wheel tyre R (A/R) is in the range of 0.55 to 0.60 and the ratio of the distance B of the axis of rotation of the lever element N from the contact point K of the contact element with the inside of the wheel tyre, in the case of a plurality of contact elements per lever element the one with the greatest distance from the axis of rotation N, to the radius of the inside of the wheel tyre R (B/R) is in the range of 0.44 to 0.55, and the sum (A+B) is greater than R. wheel of a vehicle from the deformation of the wheel tyre by contact with the roadway, comprising a) at least one lever element which is rotatably mounted at its first end and at its second end is configured to come into contact with the inside of a wheel tyre via at least one contact element in such a way that a deformation of the wheel tyre due to contact with the roadway causes a rotational movement of the lever element, b) a mechanical coupling element, which is suitable for transmitting the force generated by the rotational movement of the lever element, and c) at least one electrical generator configured to convert the transmitted power into electrical energy, a) at least one lever element which is rotatably mounted at its first end and at its second end is configured to come into contact with the inside of a wheel tyre via at least one contact element in such a way that a deformation of the wheel tyre due to contact with the roadway causes a rotational movement of the lever element, b) a mechanical coupling element, which is suitable for transmitting the force generated by the rotational movement of the lever element, and c) at least one electrical generator configured to convert the transmitted power into electrical energy, wherein at the second end of the lever element the contact element is rotatably mounted on the lever element about a rotational axis in such a way that the contact element facilitates the contact of the lever element with the wheel tyre, and the rotational axis of the contact element runs substantially parallel to the rotational axis of the wheel, characterised in that the ratio of the distance A of the axis of rotation of the lever element N from the wheel centre M to the radius of the inside of the wheel tyre R (A/R) is in the range of 0.55 to 0.60 and the ratio of the distance B of the axis of rotation of the lever element N from the contact point K of the contact element with the inside of the wheel tyre, in the case of a plurality of contact elements per lever element the one with the greatest distance from the axis of rotation N, to the radius of the inside of the wheel tyre R (B/R) is in the range of 0.44 to 0.55, and the sum (A+B) is greater than R.