Ohm's Law Ohm's law describes the relationship among voltage, V, resistance, R, and current, I, according to V = RI 12.3 Note from Ohm's law, Equation (12.3), that current is directly proportional to voltage and inversely proportional to resistance. As electric potential is increased, so is the current; and if the resistance is increased, the current will decrease. The electric resistance is measured in units of ohms (N). An element with 1 ohm resistance allows a current flow of 1 amp when there exists a potential of 1 volt across the element. Stated another way, when there exists an electrical potential of 1 volt across a conductor with a resistance of 1 ohm, then 1 ampere of electric current will flow through the conductor.

8 A 2.05 μC charged ball is placed in an electric field as shown in the figure above. The ball has a mass of 2.46 g. The electric field causes the charge to deflect 22.8°. Find the electric field that causes this deflection. E =

FLUID MECHANICS: THE ENERGY EQUATION: The attached image shows a common consumer product called a water pik. The device uses a motor to drive a piston pump that produces a jet of water (d = 3mm, T = 10oC) with a speed of 25m/s. Estimate the minimum electrical power in Watts that is required by this device. Hints: (a) Assume the power is only used to produce kinetic energy of the water in the jet. (b) In the time interval delta t, the amount of mass that flows out of the nozzle is delta m, and the corresponding amount of kinetic energy is (delta m V2/2)