Q: What is the unit of electric charge, and what is the charge of a single electron?

Coulomb; $$-1.602 \times 10$$^{-19}$$ C

Question 1

Which of the following best describes a cation?

Accepted Answer

An atom or molecule that has lost one or more electrons, resulting in a positive charge.

Question 2

According to Coulomb's law, what happens to the electrostatic force between two point charges if the distance between them is doubled?

Accepted Answer

The force decreases by a factor of 4.

Question 3

What is the unit of electric charge, and what is the charge of a single electron?

Accepted Answer

Coulomb; $$-1.602 	imes 10$$^{-19}$$ C

Question 4

Which equation correctly relates the work done ($$W) in $$moving a charge ($$Q) $$through a potential difference ($$V$$)?

Accepted Answer

$$W = QV$$

Question 5

A sodium ion ($$\mathrm{Na^+}) $$moves across a cell membrane from a region of high potential to low potential. What happens to its potential energy?

Accepted Answer

It decreases because it moves with the electric field.

Question 6

Which of the following statements about electric fields is correct?

Accepted Answer

The direction of the electric field is defined as the direction of force on a positive test charge.

Question 7

In biological systems, why is the millivolt (mV) often used instead of the volt (V) to measure membrane potential?

Accepted Answer

Because the volt is too large a unit for the small potential differences found in cells.

Question 8

Which of the following best explains why ion channels are selective for either cations or anions?

Accepted Answer

Ion channels have charged regions that attract ions of opposite charge and repel those of like charge.

Question 9

A test charge $$Q' is $$placed in an electric field $$E. $$What is the force $$F$$ experienced by the charge?

Accepted Answer

$$F = EQ'$$

Question 10

Which of the following is true about conductors in metals?

Accepted Answer

Conduction is carried by free electrons that drift in the direction of the electric field when a field is applied.

Question 11

Which of the following best describes the relationship between potential difference, energy, and charge?

Accepted Answer

Potential difference is the energy per unit charge.

Question 12

If $$1$$ volt is defined as $$1$$ joule per coulomb, which equation is correct?

Accepted Answer

$$1\ \mathrm{V} = 1\ \mathrm{J} / 1\ \mathrm{C}$$

Question 13

Which of the following is NOT a property of an electric field?

Accepted Answer

It always points from negative to positive charges.

Question 14

A negatively charged ion in an electrolyte solution will move toward which electrode during electrolysis?

Accepted Answer

The anode, because it is positively charged.

Question 15

Which of the following best explains why work must be done to bring two like charges together?

Accepted Answer

Because like charges repel each other, requiring energy to overcome the repulsive force.

Question 16

Which constant represents the charge on one mole of electrons and what is its value?

Accepted Answer

Faraday constant; $$9.648 	imes 10$$^{4}$$ C$$\cdot$$mol$$^{-1}$$

Question 17

Which of the following is a correct statement about electrolytes?

Accepted Answer

Electrolytes are compounds that dissolve in water to form a solution that conducts electricity.

Question 18

A cell membrane acts as a capacitor. Which of the following best describes this property?

Accepted Answer

It stores charge by separating positive and negative charges on either side of the membrane.

Question 19

Which of the following best describes the movement of free electrons in a metal conductor when an electric field is applied?

Accepted Answer

They drift in the direction opposite to the electric field.

Question 20

If the potential difference across a membrane is $$70 mV $$and $$2 	imes 10$$^{-9}$$ C of charge moves across it, how much work is done? (Give your answer in joules.)

Accepted Answer

$$1.4 	imes 10$$^{-10}$$ J

Electrical Properties: Charge, Electrostatics, Potential, and Conductors

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