The journey of an electron through an external circuit involves a long and slow zigzag path that is characterized by losses in electric potential. We now look extensively at resistance - the cause for these voltage drops. Resistivity is defined by the ratio of the magnitude to electric field and current density. Resistance is related to resistivity by R= rhoL/A for cylindrical conductors. Two wires - A and B - with circular cross-sections have identical lengths and are made of the same material. Yet, wire A has four times the resistance of wire B. How many times greater is the diameter of wire B than wire A?

What should the power status of a circuit be when measuring resistance with an ohmmeter?

The dot diagram represents the motion of the motorcycle as it moves from left to right

Astudent throws a water balloon with speed v0 from a height h = 1.76 m at an angle θ = 21° above the horizontal toward a target on the ground. the target is located a horizontal distance d = 9.5 m from the student’s feet. assume that the balloon moves without air resistance. use a cartesian coordinate system with the origin at the balloon's initial position. (a) what is the position vector, rtarge t, that originates from the balloon's original position and terminates at the target? put this in terms of h and d, and represent it as a vector using i and j. (b) in terms of the variables in the problem, determine the time, t, after the launch it takes the balloon to reach the target. your answer should not include h. (c) create an expression for the balloon's vertical position as a function of time, y(t), in terms of t, vo, g, and θ. (d) determine the magnitude of the balloon's initial velocity, v0, in meters per second, by eliminating t from the previous two expressions.