Copper has a density of 8.92 g/cm3 and a molar mass of 63.5 g/mol. Use these dat

Question

Copper has a density of 8.92 g/cm3 and a molar mass of 63.5 g/mol. Use these data and the fact that there are 6.02 times 1023 atoms / mol to find the number of free electrons per cubic centimeter in copper because there is one free electron per atom on the average. A 14-gauge copper wire (radius 0.0814 cm) carries a current of 1 A. Calculate the drift velocity of the electrons from the equation given in , using n from part (a) and q = e for the charge of each carrier. A galvanometer of resistance 80 Ohm gives a full-scale deflection when its current is 1.2 mA. It is used to construct an ammeter whose full-scale reading is 10 A. Find the shunt resistance needed. If the shunt resistance consists of a Piece of 10-gauge copper wire (diameter 2.59 mm), what should its length be? A sick car battery of emf 11.4 V and internal resistance 0.01 Ohm is connected to a load of 1.0 Ohm. To help the ailing battery, a second battery of emf 12.6 V and internal resistance 0.01 Ohm is connected by jumper cables to the terminals of the first battery. Draw a circuit diagram for the terminals of the first battery. Draw a circuit diagram for this situation and find the current in each part of the circuit. Find the power delivered by the second battery and discuss where this power goes, assuming that both emfs and internal resistance are constant. For the ohmmeter of Exercise 46, indicate how the galvanometer scale should be calibrated by representing the scale on a straight line of some length L, where the end of the line at x = L represents a full-scale reading of R = 0. Divide the line into 10 equal divisions and indicate the values of the resistance at each division. A Van de Graaff generator belt carries a charge of 5 muC per square meter of surface. The belt is 0.5m wide and moves at 20 m/s. What current does it carry? if this

Explanation / Answer

The galvanometer resistance, G = 80 The current throught galvanometer, ig = 1.2 * 10^-3 A The current measured, i = 10 A a) We have a formula for shunt resistance, as     S = Gig/(i - ig) = (80*1.2*10^-3) / (10 - 0.0012)     S = 0.0096 b) The diameter of the copper wire, d = 2.59 mm So the radius of the wire, r = 1.295 mm The cross sectional area of copper wire, A = r^2 = 5.27 * 10^-6 m^2 The resistivity of copper wire, = 1.68 * 10^-8 m We have formula for resistance    R = l/A    S = l/A From the above, l = SA/ = 3.01 m So the length of the wire, l = 3.01 m    S = l/A From the above, l = SA/ = 3.01 m So the length of the wire, l = 3.01 m      

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