Consider a coaxial cable, which consists of a thin wire inside a thin cylindrical conducting shell, as illustrated in the figure. The central wire carries a current Io = 10μA inwards, while the outer cylindrical shell carries a current outwards with a uniform current density Jo. The outer shell has a thickness of a = 100μ m and a radius of R = 5/3 mm. Assuming that a << R, determine the value of J, required to achieve a zero magnetic field outside the cable. [Take π = 3] R akR O a. 105 A/m² O b. 5 x 104 A/m² O c. 1 A/m² O d. 2 x 105 A/m² Oe. None of the above

A certain cylindrical wire carries current. We draw a circle of radius r around its central axis in Figure (a) to determine the current i within the circle. Figure (b) shows current i as a function of r². The vertical scale is set by is = 5.3 mA, and the horizontal scale is set by r² = 4.7 mm². (a) is the current density uniform? (b) If so, what is its magnitude? (a) (b) Number i Units i (mA) (()) (a) -² (mm²) (b)

Problem 7: A solenoid is created by wrapping a L = 35 m long wire around a hollow tube of diameter D = 4.5 cm. The wire diameter is d = 0.75 mm. The solenoid wire is then connected to a power supply so that a current of I = 4.5 A flows through the wire. Randomized Variables L= 35 m D= 4.5 cm d = 0.75 mm I= 4.5 A Part (a) Write an expression for the number of turns, N, in the solenoid. You do not need to take into account the diameter of the wire in this calculation. N = | 7 8 9. JT НOME d 1^ AL 4 5 6. a h 1 2 3 j k + END - m P VO BАСKSРАСE CLEAR DEL Submit Hint Feedback I give up! Part (b) Calculate the number of turns, N, in the solenoid. Part (c) Write an expression for the length of the solenoid (L2) in terms of the diameter of the hollow tube D, the length of the wire L and the diameter of the wire d. Assume it is constructed by using only 1 layer of loops (note that most solenoids are actually constructed with many layers, to maximize the magnetic field density). Part (d)…

A caterpillar of length 6.00 cm crawls in the direction of electron drift along a 8.20-mm-diameter bare copper wire that carries a uniform current of 38.0 A. (a) What is the potential difference between the two ends of the caterpillar? (b) Is its tail positive or negative relative to its head? (c) How much time does the caterpillar take to crawl 2.30 cm if it crawls at the drift speed of the electrons in the wire? (The number of charge carriers per unit volume is 8.49 × 1028 m-3 and resistivity of copper is 1.69 × 10-8 Ω·m.)

The current flowing in a given circuit can be described by the function: I(t) = Imax(1 - e-t/τ), where Imax = 25 A and T = 2.4 s. At what time in seconds is the current equal to 75% of the maximum current? How much charge in coulombs, passes through a point in the circuit as the current increases from 0 to 75% of the maximum current?