Monday February 23

Lecture 15RC Circuits

Electricity in the Nervous System

Capacitor Combinations

Slide 23-24

Which of the following combinations of capacitors has the highest capacitance?

A B C D

25% 25%25%25%

1. A2. B3. C4. D

Which of the following combinations of capacitors has the lowest capacitance?

A B C D

25% 25%25%25%

1. A2. B3. C4. D

Which of the following combinations of capacitors has the lowest capacitance?

A B C D

25% 25%25%25%

1. A2. B3. C4. D

RC Circuit

• Charge or discharge a capacitor, C, through a resistor, R.

• Start with discharge: See diagram• R=40,000Ω• C= 3000 μF• E = 3.0 V

What current flows just after switch is closed (t=0)?

• E = 3 V and Vc = 0, so I = E/R = 3.0/300=.01 A• What is charge on C at t=0.01 s? (approx)

At t = 0.01 s

• Q(.01) = Q(0)-I(0)*.01 = ?– What is Vc(0.01) ?

• Q(.02) = ?– Vc(0.02) ?

All capacitors have V0 = 5.0v at t=0 when switches are closed. Which has the lowest voltage at t = 1s?

A B C D

25% 25%25%25%

1. A2. B3. C4. D