Chapter 26, Problem 7Q

25.12     A Copper wire has a square cross section 2.3 mm on a side. The wire is 4.0 m long and carries a current of 3.6 A. The density of free electrons is 8.5 X 1028/m3.   Find the magnitudes of (a) the current density in the wire and (b) the electric field in the wire. (c) How much time is required for an electron to travel the length of the wire?

A current is established in a gas discharge tube when a sufficiently high potential difference is applied across the two electrodes in the tube.The gas ionizes; electrons move toward the positive terminal and singly charged positive ions toward the negative terminal. (a) What is the current in a hydrogen discharge tube in which 3.1 *10^18 electrons and 1.1* 10^18 protons move past a crosssectional area of the tube each second? (b) Is the direction of the current density toward or away from the negative terminal?

An isolated conducting sphere has a 11 cm radius. One wire carries a current of 1.0000023 A into it while another wire carries a current of 1.0000000 A out of it. How long in seconds would it take for the sphere to increase in potential by 1000 V?

Problem 1:  A cell phone battery uses chemistry to create a charge separation between the terminals (anode and cathode). Such a battery is listed as having a capacity of Q = 7.5E-08 C.  Part (a)  How many free electrons does the battery contain, N? Part (b)  If there are 1.0 million electrons moving through the phone every second how long will the battery last in seconds? Part (c)  Current, I, is given in amps which are coulombs per second. What is the current passing through the phone?

The drift speed in a copper wire is 7.15 x 105 m/s for a typical electron current. Calculate the magnitude of the electric field E inside the copper wire. The mobility of mobile electrons in copper is 4.5 x 10-3 (m/s)/(N/C). (Note that though the electric field in the wire is very small, it is adequate to push a sizable electron current through the copper wire.) i N/C eTextbook and Media

28 1 6.0 x 10 m3 1. Consider a cylindrical wire that has conduction electron density and radius 0.5 mm. An electric field with strength 7.5 x 10-4 creates a current of 4.8 x 10 electrons per second. a) What is the average drift speed for an electron? (include units) b) What is the average time in between electron collisions? fs (express your answer in femtoseconds)

In the figure,E₁ = 6.00 V, E₂= 12.0 V, R₁ = 100 S2, R₂ = 200 S, and R3 = 300 2. What are the (a) size and direction (up or down) of the current through R₁, the (b) size and direction (left or right) of the current through R2, and the (c) size and direction (left or right) of the current through R3? www Ro E₁ M R₁ www R3 E2

A charge crossing a surface due to a proton beam is given by Q = 5.0t3 + 3.0t2 + 8.0 where Q is measured in Coulombs and the time t is measured in seconds. What is the current due to the proton beam when t = 3.0 s. О (а) 459 A О (b) 153 А O (c) 297 A O (d) 99 A O (e) 56.7 A

A coaxial cable is made up of two conductors, one which has a radius of 1.5 cm (inner conductor) and one which has a radius of 5 cm (outer conductor). The space between the two conductors is filled with a medium. The length of the cable is 200 m. A potential difference of 3 kV is maintained between the conductors.a) Use the analogy between the electric flux density and conduction current density fields to calculate the current through the medium (medium which is characterised by Er = 1.8 and σ = 10 µS/m).b) Calculate the power dissipated in the medium