An unknown wire in a circuit has a circular cross-section with diameter 3.8 mm. It carries a current of 4.2 mA. If you assume the drift velocity in this wire is 1 × 10-2 cm/s, what is the density of charge carriers per cubic centimeter?  If the conductivity in this wire is 3.5 × 106 Ω-1 m-1, what is the average time between

What is the total resistance (sum) of the two wires? Express your answer to two significant figures and include the appropriate units. rtotal=   What is the current through the wire? Express your answer to two significant figures and include the appropriate units. I=

Figure a shows a rod of resistive material. The resistance per unit length of the rod increases in the positive direction of the X axis. At any position x along the rod, the resistance dR of a narrow- differential-section of width dx is given by dR = 5.00xdx, where dR is in ohms and is in meters. Figure b shows such a narrow section. You are to slice off a length of the rod between X = O and some position = L and then connect that length to a battery with potential difference V = 5.0V (Fig. c). You want the current in the length to transfer energy to thermal energy at the rate of 6.2 W. At what position x = L in meters should you cut the rod? Keep 2 decimla points in your aanswer. dx 1.0 -x (m)

A 14-gauge copper wire has a diameter of 1.508 mm. What magnitude current flows in amperes when the drift velocity is 0.500 mm/s? (The density of free electrons in copper is 8.34 x 1028 e /m³.).) A