Q: If the electric field inside a parallel-plate capacitor is $$2.0 \times 10^6$ N/C, the area of each plate is 2.0$$ \times $$10^{-4} m$^2$$, and $$\$$epsilon_0$$ = 8.85 \times 10$$^{-12}$$ C^2$/Nm^2$, what charge must be placed on each plate?

$$\3.5$$ \times $$10^{-9}$$\$ C

Question 1

Which of the following best describes the direction of the electric field produced by a positive point charge?

Accepted Answer

The electric field points radially outward away from the charge.

Question 2

A test charge $$q$$ experiences a force $$\vec{F}_{on\,q} in an $$electric field. What is the correct formula for the electric field at the location of the test charge?

Accepted Answer

$$\$$\vec{E} = \frac{\vec{F}_{on\,q}}{q}\$

Question 3

What is the SI unit of the electric field?

Accepted Answer

Newton per coulomb (N/C)

Question 4

Which equation gives the magnitude of the electric field at a distance $$r$$ from a point charge $$q$$?

Accepted Answer

$$\E$$ = \frac{q}{4\pi\$$epsilon_0$$ $$r^2$$}\$

Question 5

A group of point charges $$q_1$$, $$q_2$$, ...$$ produces an electric field at a point. What principle allows you to find the net electric field?

Accepted Answer

The principle of superposition

Question 6

Two equal but opposite charges are separated by a small distance $$s. $$What is the dipole moment $$\vec{p} of $$this system?

Accepted Answer

$$\$$\vec{p} = qs\$$  ($$from negative to positive charge)

Question 7

What is the electric field at a point on the axis of an electric dipole at a distance $$r$$ from its center (where $$r \gg s$$)?

Accepted Answer

$$\E$$_{dipole} \approx \frac{1}{4\pi\$$epsilon_0$$} \frac{2p}{$$r^3$$}\$

Question 8

Which of the following statements about electric field lines is FALSE?

Accepted Answer

Electric field lines can form closed loops.

Question 9

A parallel-plate capacitor has plates of area $$A$$ and charge $$\pm Q. $$What is the magnitude of the electric field inside the capacitor?

Accepted Answer

$$\E$$ = \frac{Q}{\$$epsilon_0 A$$}\$

Question 10

Which of the following best describes the electric field outside an ideal parallel-plate capacitor?

Accepted Answer

The electric field is zero.

Question 11

A proton and an electron are placed in the same uniform electric field. Which statement is correct about their accelerations?

Accepted Answer

The electron has a larger acceleration magnitude than the proton.

Question 12

A water molecule has a permanent dipole moment of $$6.2 	imes 10$$^{-30}$$ C·m. What is the electric field strength at a point 1.0 nm from the molecule on its axis? (Use $$\frac{1}{4\pi\$$epsilon_0$$} = 9.0 	imes $$10^9 Nm$^2/C$^2)$$

Accepted Answer

$$\1.1$$ 	imes $$10^8$$\$ N/C

Question 13

Which of the following is a real-world application of the motion of charged particles in a uniform electric field?

Accepted Answer

Gel electrophoresis for DNA fingerprinting

Question 14

If the electric field inside a parallel-plate capacitor is $$2.0 	imes 10^6$ N/C, the area of each plate is 2.0$$ 	imes $$10^{-4} m$^2$$, and $$\$$epsilon_0$$ = 8.85 	imes 10$$^{-12}$$ C^2$/Nm^2$, what charge must be placed on each plate?

Accepted Answer

$$\3.5$$ 	imes $$10^{-9}$$\$ C

Question 15

Which of the following is TRUE about the electric field at different points inside a parallel-plate capacitor?

Accepted Answer

The electric field is the same at all points inside the capacitor.

Question 16

A charged particle of mass $$m$$ and charge $$q is $$placed in a uniform electric field $$\vec{E}. $$What is its acceleration?

Accepted Answer

$$\a$$ = \frac{qE}{m}\$

Question 17

Which of the following best describes the electric field lines for a dipole?

Accepted Answer

They start on the positive charge and end on the negative charge, curving outward.

Question 18

In the context of the electric field of multiple point charges, what is the first step in the recommended problem-solving strategy?

Accepted Answer

Establish a coordinate system and show the locations of the charges.

Chapter 23: The Electric Field – Study Notes

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