Question 1

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

Accepted Answer

The electric field points radially inward toward the charge.

Question 2

A test charge $$q_0 is $$placed at a point $$P$$ near a positive point charge $$q. $$What is the direction of the electric field at $$P$$?

Accepted Answer

Away from the source charge $$q$$

Question 3

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

Accepted Answer

$$ \vec{E} = k \frac{q}{r^2} \hat{r} $$

Question 4

If two equal negative charges are placed at two vertices of an equilateral triangle, what is the direction of the electric field at the third vertex?

Accepted Answer

Down the page (toward the base of the triangle)

Question 5

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

Accepted Answer

Electric field lines originate from positive charges and terminate on negative charges.

Question 6

What is the SI unit of electric field strength?

Accepted Answer

Newton per Coulomb ($$ \mathrm{N/C} )$$

Question 7

A continuous line of charge has a linear charge density $$\lambda. $$What is the infinitesimal charge element $$dq'$$ over a small length $$dx'$$?

Accepted Answer

$$ dq' = \lambda dx' $$

Question 8

Which of the following best explains why the electric field from a point charge decreases with distance?

Accepted Answer

The field spreads out over a larger area as distance increases, so its strength decreases as $$1/r^2.$$

Question 9

A system consists of three point charges. How do you find the net electric field at a point due to all three charges?

Accepted Answer

By vector addition (superposition) of the electric fields from each charge at that point.

Question 10

Which of the following is a correct statement about the electric field at a point due to a system of charges?

Accepted Answer

The net electric field is the vector sum of the fields produced by each charge at that point.

Question 11

A uniform ring of positive charge lies in the $$xy-$$plane. What is the direction of the electric field at a point along the $$z-$$axis passing through the center of the ring?

Accepted Answer

Along the $$z-$$axis, away from the ring if the point is above the plane

Question 12

Which of the following best describes the process of dielectric breakdown in air?

Accepted Answer

Electrons are freed from atoms by a strong electric field, leading to ionization and a cascade of further ionizations.

Question 13

A positive test charge $$q_0 is $$placed in an electric field $$\vec{E}. $$What is the force experienced by the test charge?

Accepted Answer

$$ \vec{F} = q_0 \vec{E} $$

Question 14

Which of the following is NOT a correct method for calculating the electric field due to a continuous charge distribution?

Accepted Answer

Multiplying the total charge by the distance from the point of interest.

Question 15

A thin rod of length $$L$$ has a uniform linear charge density $$\lambda. $$What is the total charge on the rod?

Accepted Answer

$$ Q = \lambda L $$

Question 16

If the electric field at a point is $$5 	imes 10^6$ N/C, what is the force on a 2$$ \mu$$C charge placed at that point?

Accepted Answer

$$ F = (2 	imes 10^{-6} \ \mathrm{C}) 	imes (5 	imes 10^6 \ \mathrm{N/C}) = 10 \ \mathrm{N} $$

Question 17

Which of the following is a property of conductors in electrostatic equilibrium?

Accepted Answer

Total charge does not change and can be sent to or drawn from ground.

Question 18

A point charge $$q is $$located at the origin. At what distance $$r$$ from the charge does the electric field have a magnitude $$E$$?

Accepted Answer

$$ r = \sqrt{\frac{kq}{E}} $$

Question 19

Which of the following best describes the relationship between electric field vectors and electric field lines?

Accepted Answer

Electric field vectors are tangent to electric field lines at every point.

Electric Fields – Physics 1200 Lecture 02 Study Notes

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