A heat dissipating apparatus includes a rear cove, a fan rotatably attached to the rear cover, a slave gear secured to the fan, and a driving gear rotatably attached to the rear cover. The rear cover defines a plurality of air ventilation holes. The fan is aligned with the plurality of air ventilation holes. The driving gear meshes with the driven gear. A resilient member is secured to the driving member. The driving gear is rotatable in a first direction to deform the resilient member. The resilient member is released to rotate the driving gear in a second direction that is opposite to the first direction, and the slave gear and the fan are together rotatable in the second direction by the driving gear.