During operation, a device sprays droplets of aqueous liquid of average diameter 100 um and charge density p = 30 mC.kg¬1. 1. Express the mass of a droplet as a function of its diameter d and the mass density My of the liquid. 2. Assuming that the mass density of a hydroalcoholic solution is the same as that of water, calculate the mass of a droplet of sprayed liquid. 3. Express the charge Q of a droplet as a function of the charge density per unit mass p and the mass of that droplet. Deduce the average charge carried by a droplet using p= 30 mC.kg¬1. 4. Has the droplet lost or gained electrons? How many electrons does this charge represent ?

During operation, a device sprays droplets of aqueous liquid of average diameter 100 um and charge density p = 30 mC.kg¬1. 1. Express the mass of a droplet as a function of its diameter d and the mass density My of the liquid. 2. Assuming that the mass density of a hydroalcoholic solution is the same as that of water, calculate the mass of a droplet of sprayed liquid. 3. Express the charge Q of a droplet as a function of the charge density per unit mass p and the mass of that droplet. Deduce the average charge carried by a droplet using p= 30 mC.kg¬1. 4. Has the droplet lost or gained electrons? How many electrons does this charge represent ?