Q: A nerve cell membrane can be modeled as a capacitor. If the membrane has a capacitance of $$100\,\mathrm{pF}$$ and a resistance of $$1 \times 10^7$\,\Omega$$, what is the time constant for the membrane?

$$1 \times 10$$^{-3}$$\,\mathrm{s}$$

Question 1

Which of the following statements about Kirchhoff's junction rule is correct?

Accepted Answer

It states that the total current entering a junction equals the total current leaving the junction.

Question 2

A circuit consists of a $$12\,\mathrm{V}$$ battery and two resistors, $$R_1 = 4$$\,\Omega$$ and R_2$ = 8\,\Omega$$, connected in series. What is the current through the circuit?

Accepted Answer

$$0.5\,\mathrm{A}$$

Question 3

Which of the following is true for resistors connected in parallel?

Accepted Answer

The potential difference across each resistor is the same.

Question 4

A $$10\,\Omega$$ and a $$20\,\Omega$$ resistor are connected in parallel across a $$10\,\mathrm{V}$$ battery. What is the total current supplied by the battery?

Accepted Answer

$$1.0\,\mathrm{A}$$

Question 5

Which equation correctly gives the equivalent resistance $$R_{eq}$$ for three resistors $$R_1$$, $$R_2$$, and $$R_3 in $$parallel?

Accepted Answer

$$\dfrac{1}{R_{eq}} = \dfrac{1}{R_1$} + \dfrac{1}{R_2$} + \dfrac{1}{R_3$}$$

Question 6

A circuit contains a $$9\,\mathrm{V}$$ battery, a $$3\,\Omega$$ resistor, and a $$6\,\Omega$$ resistor in series. What is the potential difference across the $$6\,\Omega$$ resistor?

Accepted Answer

$$6\,\mathrm{V}$$

Question 7

Which of the following best describes the function of an ideal ammeter in a circuit?

Accepted Answer

It measures the current through a circuit element and is connected in series.

Question 8

A $$2\,\mu\mathrm{F}$$ and a $$4\,\mu\mathrm{F}$$ capacitor are connected in series. What is their equivalent capacitance?

Accepted Answer

$$1.33\,\mu\mathrm{F}$$

Question 9

In an RC circuit, the time constant $$	au is $$given by which of the following expressions?

Accepted Answer

$$	au = RC$$

Question 10

A $$10\,\mu\mathrm{F}$$ capacitor is charged to $$12\,\mathrm{V}. $$How much charge is stored on the capacitor?

Accepted Answer

Question 11

A nerve cell membrane can be modeled as a capacitor. If the membrane has a capacitance of $$100\,\mathrm{pF}$$ and a resistance of $$1 	imes 10^7$\,\Omega$$, what is the time constant for the membrane?

Accepted Answer

$$1 	imes 10$$^{-3}$$\,\mathrm{s}$$

Question 12

Which of the following best explains why the equivalent resistance of resistors in parallel is always less than the resistance of any individual resistor?

Accepted Answer

Because parallel resistors provide more paths for current to flow.

Question 13

In a complex circuit, two $$10\,\Omega$$ resistors are in parallel, and this combination is in series with a $$5\,\Omega$$ resistor. What is the total resistance of the circuit?

Accepted Answer

Question 14

Which of the following statements about the myelin sheath in nerve cells is correct?

Accepted Answer

It increases the speed of nerve impulse propagation by reducing capacitance and increasing resistance between nodes.

Question 15

A $$5\,\Omega$$ resistor and a $$10\,\Omega$$ resistor are connected in series to a $$15\,\mathrm{V}$$ battery. What is the voltage drop across the $$10\,\Omega$$ resistor?

Accepted Answer

$$10\,\mathrm{V}$$

Question 16

Which of the following is the correct formula for the charge $$Q on a $$capacitor of capacitance $$C$$ connected to a battery of voltage $$V$$?

Accepted Answer

$$Q = CV$$

Question 17

In an RC circuit, the current as a function of time while charging the capacitor is given by:

Accepted Answer

$$I(t) = \dfrac{E}{R} e$$^{-t/RC}$$

Question 18

A voltmeter is used to measure the potential difference across a resistor in a circuit. How should it be connected?

Accepted Answer

In parallel with the resistor

Chapter 23: Circuits – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards