Q: A cell membrane has a potential difference of $$70\ \text{mV}$$ across a thickness of $$7.0\ \text{nm}. $$What is the electric field inside the membrane?

$$1.0 \times 10^7$\ \text{V/m}$$

Q: During an action potential, which ion movement causes depolarization of the nerve cell membrane?

Sodium ions ($$\text{Na}^+) $$move into the cell.

Question 1

A wire carries a current of 5.0 A. How much charge passes through a cross-section of the wire in 10 seconds?

Accepted Answer

$$50\ 	ext{C}$$

Question 2

Which statement best describes the direction of conventional current in a metallic wire?

Accepted Answer

It is opposite to the direction of electron flow.

Question 3

A copper wire has length $$L$$ and cross-sectional area $$A. If $$the wire is replaced with one of the same length but half the area, what happens to its resistance?

Accepted Answer

Resistance doubles.

Question 4

A resistor is connected across a 9 V battery and carries a current of 3 A. What is its resistance?

Accepted Answer

$$3\ \Omega$$

Question 5

Which equation correctly expresses Ohm’s law?

Accepted Answer

$$V = IR$$

Question 6

A 60 W light bulb is connected to a 120 V supply. What current does it draw?

Accepted Answer

$$0.5\ 	ext{A}$$

Question 7

Two batteries, each with emf $$1.5\ 	ext{V}$$, are connected in series. What is the total potential difference across their terminals?

Accepted Answer

$$3.0\ 	ext{V}$$

Question 8

Three resistors, $$R_1 = 2$$\ \Omega$$, R_2$ = 4\ \Omega$$, and $$R_3 = 6$$\ \Omega$$, are connected in series. What is their equivalent resistance?

Accepted Answer

$$12\ \Omega$$

Question 9

Two resistors, $$R_1 = 8$$\ \Omega$$ and R_2$ = 4\ \Omega$$, are connected in parallel. What is their equivalent resistance?

Accepted Answer

$$\displaystyle 1/\left(1/8 + 1/4\right) = 2.67\ \Omega$$

Question 10

In a parallel circuit, which quantity is the same across all branches?

Accepted Answer

Voltage

Question 11

A circuit contains a $$10\ \Omega$$ resistor and a $$5\ \Omega$$ resistor in series, connected to a $$30\ 	ext{V}$$ battery. What is the current in the circuit?

Accepted Answer

$$2\ 	ext{A}$$

Question 12

A $$12\ 	ext{V}$$ battery is connected to two resistors in parallel: $$R_1 = 6$$\ \Omega$$ and R_2$ = 3\ \Omega. $$What is the total current supplied by the battery?

Accepted Answer

$$6\ 	ext{A}$$

Question 13

Which statement about current in a closed circuit is correct?

Accepted Answer

Current is conserved; it does not get used up.

Question 14

A cell membrane has a potential difference of $$70\ 	ext{mV}$$ across a thickness of $$7.0\ 	ext{nm}. $$What is the electric field inside the membrane?

Accepted Answer

$$1.0 	imes 10^7$\ 	ext{V/m}$$

Question 15

Which formula gives the time constant for an RC circuit?

Accepted Answer

$$	au = RC$$

Question 16

A capacitor with capacitance $$C is $$charged to voltage $$V. $$What is the stored charge?

Accepted Answer

$$Q = CV$$

Question 17

Which arrangement correctly describes how capacitors combine in parallel?

Accepted Answer

$$C_{eq} = C_1$ + C_2$ + \cdots$$

Question 18

A nerve cell membrane can be modeled as which type of circuit?

Accepted Answer

An RC circuit

Question 19

During an action potential, which ion movement causes depolarization of the nerve cell membrane?

Accepted Answer

Sodium ions ($$	ext{Na}^+) $$move into the cell.

Question 20

A circuit contains a $$4\ \Omega$$ resistor in series with a parallel combination of $$6\ \Omega$$ and $$3\ \Omega$$ resistors, connected to a $$12\ 	ext{V}$$ battery. What is the total current supplied by the battery?

Accepted Answer

$$2\ 	ext{A}$$

Electric Current, Resistance, Circuits, and Bioelectricity: Study Notes

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