Problem 52E

Resistors to be used in a circuit have average resistance 200 ohms and standard deviation 10 ohms. Suppose 25 of these resistors are randomly selected to be used in a circuit. a What is the probability that the average resistance for the 25 resistors is between 199 and 202 ohms?

b Find the probability that the total resistance does not exceed 5100 ohms. [Hint: see Example 7.9.]

Reference

PHY 184 Week 6 Notes-Currents and Resistance 10/3-10/6 The battery produces a constant voltage When closed the current is able to flow o Don’t forget only the electrons move In the absence of an electric field electrons move randomly within the conductor o When an electric field is applied electrons get an additional velocity called drift velocity It is 10 times slower than thermal velocity How is it almost instant then o Closing the current starts an electric field and sets the electrons in motion Charge Carriers Consider a conductor with cross section A and electric field E Suppose there are n positive carriers per unit volume, all evenly distributed in the same dV with drift velocity v