Q: A point charge of $$500\ \mu C is $$placed at the origin. What is the electric potential at a point $$50\ \text{cm}$$ away from the charge? (Assume $$k = 8.99 \times 10^9$\ \text{N} \cdot \text{m}^2/\text{C}^2)$$

$$8.99 \times 10^7$\ \text{V}$$

Q: A $$2.0\ \mu F$$ capacitor is charged to $$2.0\ \text{V}$$ and then discharged in $$0.01\ \text{s}. $$What is the average current during the discharge?

$$4.0 \times 10$$^{-3}$$\ \text{A}$$

Q: If the electric field inside a cell membrane is $$2.0 \times 10^7$\ \text{V/m}$$ and the membrane thickness is $$7.2\ \text{nm}$$, what is the potential difference across the membrane?

$$1.44 \times 10$$^{-1}$$\ \text{V}$$

Q: If a $$5.0\ \mu C$$ charge is placed at a point where the electric potential is $$1.0 \times 10^4$\ \text{V}$$, what is the electric potential energy of the charge?

$$5.0 \times 10$$^{-2}$$\ \text{J}$$

Q: A parallel plate capacitor has plates of area $$0.01\ \text{m}^2$$ separated by $$1.0\ \text{mm}$$ and filled with a dielectric of $$\kappa = 5.0. $$What is its capacitance? ($$\$$epsilon_0$$ = 8.85 \times 10$$^{-12}$$\ \text{F/m})$$

$$4.4 \times 10$$^{-10}$$\ \text{F}$$

Q: A cell membrane has a potential difference of $$70\ \text{mV}$$ across a thickness of $$7.2\ \text{nm}. $$What is the magnitude of the electric field inside the membrane?

$$9.7 \times 10^6$\ \text{V/m}$$

Question 1

A point charge of $$500\ \mu C is $$placed at the origin. What is the electric potential at a point $$50\ 	ext{cm}$$ away from the charge? (Assume $$k = 8.99 	imes 10^9$\ 	ext{N} \cdot 	ext{m}^2/	ext{C}^2)$$

Accepted Answer

$$8.99 	imes 10^7$\ 	ext{V}$$

Question 2

Which of the following best describes the direction of the electric field at a point near a positive point charge?

Accepted Answer

It points away from the charge.

Question 3

A $$2.0\ \mu F$$ capacitor is charged to $$2.0\ 	ext{V}$$ and then discharged in $$0.01\ 	ext{s}. $$What is the average current during the discharge?

Accepted Answer

$$4.0 	imes 10$$^{-3}$$\ 	ext{A}$$

Question 4

A heater is designed to use $$500\ 	ext{W}$$ when connected to $$120\ 	ext{V}. $$What is the resistance of the heater?

Accepted Answer

$$28.8\ \Omega$$

Question 5

If the electric field inside a cell membrane is $$2.0 	imes 10^7$\ 	ext{V/m}$$ and the membrane thickness is $$7.2\ 	ext{nm}$$, what is the potential difference across the membrane?

Accepted Answer

$$1.44 	imes 10$$^{-1}$$\ 	ext{V}$$

Question 6

Which of the following is the correct relationship for the capacitance $$C of a $$parallel plate capacitor with area $$A$$, plate separation $$d$$, and dielectric constant $$\kappa$$?

Accepted Answer

$$C = \kappa \$$epsilon_0$$ \frac{A}{d}$$

Question 7

A copper wire of length $$4.0\ 	ext{m}$$ and diameter $$0.50\ 	ext{mm} is $$used in a heater. If the resistivity of copper is $$1.47 	imes 10$$^{-8}$$\ \Omega \cdot 	ext{m}$$, what is the resistance of the wire?

Accepted Answer

$$0.30\ \Omega$$

Question 8

If a $$5.0\ \mu C$$ charge is placed at a point where the electric potential is $$1.0 	imes 10^4$\ 	ext{V}$$, what is the electric potential energy of the charge?

Accepted Answer

$$5.0 	imes 10$$^{-2}$$\ 	ext{J}$$

Question 9

Which of the following statements about current in a simple circuit is correct?

Accepted Answer

Current is the flow of electrons from the negative to the positive terminal.

Question 10

A parallel plate capacitor has plates of area $$0.01\ 	ext{m}^2$$ separated by $$1.0\ 	ext{mm}$$ and filled with a dielectric of $$\kappa = 5.0. $$What is its capacitance? ($$\$$epsilon_0$$ = 8.85 	imes 10$$^{-12}$$\ 	ext{F/m})$$

Accepted Answer

$$4.4 	imes 10$$^{-10}$$\ 	ext{F}$$

Question 11

If the potential difference across a resistor is doubled, what happens to the power dissipated by the resistor?

Accepted Answer

It is quadrupled.

Question 12

Which of the following best describes the function of a capacitor in a defibrillator circuit?

Accepted Answer

It stores electrical energy to be released quickly.

Question 13

A cell membrane has a potential difference of $$70\ 	ext{mV}$$ across a thickness of $$7.2\ 	ext{nm}. $$What is the magnitude of the electric field inside the membrane?

Accepted Answer

$$9.7 	imes 10^6$\ 	ext{V/m}$$

Question 14

Which of the following is a correct statement about the direction of the electric field in a cell membrane?

Accepted Answer

It points from the outside to the inside of the cell.

Question 15

If a $$-6.0 	imes 10$$^{-19}$$\ 	ext{C}$$ charge is placed in an electric field of $$9.7 	imes 10^6$\ 	ext{V/m}$$, what is the force on the charge?

Accepted Answer

$$-5.8 	imes 10$$^{-12}$$\ 	ext{N}$$

Question 16

Which prefix corresponds to $$10^{-6}$$?

Accepted Answer

micro

Question 17

A battery is connected to two resistors in parallel, each of $$2\ \Omega. $$What is the equivalent resistance?

Accepted Answer

$$1\ \Omega$$

Question 18

Which of the following best describes the energy transformation in a resistor?

Accepted Answer

Electrical energy is converted to heat.

PHYS 202 Exam II Study Guidance: Electric Potential, Circuits, Capacitance, and Electric Fields

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