in a contacts closed position of a circuit breaker, a main body portion (224) of a contact arm (208) engages a main contact (218). Upon movement of the contacts towards an open position, an end portion (225) of the contact arm (208) moves into engagement with a tubular arcing electrode (221) before the main body portion (224) disengages from the main contact (218). Subsequently, the end portion (225) disengages from the arcing electrode (221) so that an arc is drawn therebetween, and the arcing current flows through a field coil (223) creating a magnetic field which causes the arc to rotate and become extinguished. In the contacts open position of the circuit breaker, the end portion (225) lies along the axis of the field coil (223). In an alternative construction, the end portion of the contact arm engages the arcing electrode when the contacts are in their closed position, and remains in such engagement for some time after the main body portion has disengaged from the main contact.