Resumen de Why Does a Stream of Water Deflect in an Electric Field?
G. K. Vemulapalli, Stephen G. Kukolich
A popular lecture demonstration shows a stream of water bending in the presence of an electrified object. We have quantitatively analyzed this phenomenon after experimenting with controlled electric fields. The following are our conclusions. (i) The electric field must be nonuniform for this effect to be observed. The electric force is proportional to the product of the field and its gradient. In case of water, these are of the order of 105 V m-1 and 108 V m-2. (ii) The effect is readily observed with water because the gravitational force opposing the deflection is small due to lighter mass of water molecules. (iii) Since electric fields induce dipole moments, even nonpolar molecules show deflection if the field is strong enough. Statements in many textbooks about this phenomenon are misleading since they do not point out the importance of nonunimformity of the field, the relative magnitudes of gravitational and electric forces, and the possibility that induced dipoles also undergo deflection.
