Physics for the Inquiring Mind (PHYS 105)                Fall 2005 Exercises for Friday, October 14. [1] Using the parallel rule for adding resistances, predict the total resistance when a 39 Ohm resistor is hooked in parallel with an 82 Ohm resistor. [2] Hook up your 39 Ohm and 82 Ohm resistors in parallel, and check your prediction. [3] Now predict the resistance when 27 Ohm, 39 Ohm, and 47 Ohm resistors are all hooked in parallel.  Again, check your prediction. [4] Look at the circuit below, in which the left Ammeter is measuring the current through the 10 Ohm resistor, and the right Ammeter is measuring the current through the 100 Ohm resistor. When this circuit is set up, how do you think the readings on the two ammeters will compare?  Be quantitative in your prediction.  That is, say “They will be the same”, or “The left one will read 6 times the current of the right one”, or something similar.  Don't just say “The left one will read more current than the right”. [5] Check the prediction you made in part [4] by setting up the circuit. [6] Now predict how the currents in the ammeters of this circuit will compare. Check your prediction. [7] State a rule describing how current splits when it is given a choice of two paths. [8] As homework for Tuesday, October 18, complete Exercise 5.7 on page 425 and Problem 6.2 on page 504.  For Problem 6.2, don't be confused by the “cm”.  You can replace them by Ohms if you wish.