There is a grounding wire that separates a 2 prong power cord from a 3 prong power cord. Two wires, one live and the other neutral, are used in a 2 prong power cord which is usually applied to appliances without safety requirement for grounding. On the other hand, an extra ground wire is added into three-pronged cords so as to minimize electric shock hazards thereby being widely used for appliances or equipment that must be grounded in order to operate safely.