Circuit breaker comprising: - at least a first contact branch comprising at least a first contact element and at least a first support element of the first contact element, at least a first connection terminal electrically connected to, or integrated into, the first support element; - an actuating mechanism of the first support element adapted to move the latter so that the first contact element can be moved from a rest position to a working position and vice versa; - a second contact branch comprising at least a second contact element, adapted to be contacted by the first contact element when this is in the working position, at least a second support element of the second contact element and at least a second connection terminal electrically connected to, or integrated into, the second support element; wherein the circuit breaker further comprises an electrically insulating mobile barrier adapted to be moved between: - a first operating position wherein the mobile barrier allows the second contact element to be contacted by the first contact element; and - a second operating position wherein the mobile barrier is at least partially operatively interposed between the first contact element and the second contact element to interfere, in the passage of the first contact element from the working position to the rest position, with an electric arc that extends between said contact elements; characterized in that: the second support element comprises a movable arm adapted to rotate about an axis of rotation and wherein the circuit breaker further comprises at least one elastic element acting on the movable arm and configured to maintain, in a condition of regular operation of the circuit breaker, the second contact element as close as possible to the first contact element when the latter is in the working position. - at least a first contact branch comprising at least a first contact element and at least a first support element of the first contact element, at least a first connection terminal electrically connected to, or integrated into, the first support element; - an actuating mechanism of the first support element adapted to move the latter so that the first contact element can be moved from a rest position to a working position and vice versa; - a second contact branch comprising at least a second contact element, adapted to be contacted by the first contact element when this is in the working position, at least a second support element of the second contact element and at least a second connection terminal electrically connected to, or integrated into, the second support element; - a first operating position wherein the mobile barrier allows the second contact element to be contacted by the first contact element; and - a second operating position wherein the mobile barrier is at least partially operatively interposed between the first contact element and the second contact element to interfere, in the passage of the first contact element from the working position to the rest position, with an electric arc that extends between said contact elements; the second support element comprises a movable arm adapted to rotate about an axis of rotation and wherein the circuit breaker further comprises at least one elastic element acting on the movable arm and configured to maintain, in a condition of regular operation of the circuit breaker, the second contact element as close as possible to the first contact element when the latter is in the working position.