Question

15. Estimate the resistance ? of a standard (not a high-speed) phone charging cable.

?=_____Ω

19. A certain single ion channel is selectively permeable to K+ and has a resistance of 1.15 GΩ , therefore a current of potassium ions through the channel is possible. During an experiment, the channel is open for approximately 1.50 ms while the voltage across the channel is maintained at 89.5 mV . How many K+ ions travel through the channel during this time?

number of K+ ions:

21. Find the equivalent resistance of the combination of resistors ?1=42.0 Ω , ?2=75.0 Ω , ?3=33.0 Ω , ?4=61.0 Ω , ?5=12.5 Ω , and ?6=33.0 Ω , as shown in the figure.

equivalent resistance: ________Ω

22. The four resistors in the figure have an equivalent resistance of 16Ω. The resistances are as follows: ?1=12Ω, ?2=6.0Ω, and ?3=2.0Ω. Calculate the value of ?x.

?x=_______Ω

34. You charge an initially uncharged 78.7-mF capacitor through a 36.9-Ω resistor by means of a 9.00-V battery having negligible internal resistance. Find the time constant ? of the circuit.

?=________ s

What is the charge ? on the capacitor 1.49 time constants after the circuit is closed?

?=_______C

What is the charge ?0 after a long amount of time has passed?

?0=________C

Answer 1