Chapter 8 - Electrostatics and Electromagnetism

Question 1

What are electric field lines? What is their directionality and strength?

Answer 1

They are lines of force representing an electric field. They always originate on a positive charge and end on a negative charge. They represent the way a positive charge would migrate. Field lines close together mean the electric field is strong, whereas field lines farther apart mean the electric field is weak.

Question 2

What is a test charge (q’)?

Answer 2

an arbitrary positive charge with an electric field

Question 3

Equation: Faraday’s law of electromotive force

Answer 3

emf = -Δφ_B/Δt

φ_B = magnetic flux

Question 4

Equation: electric dipole moment

Answer 4

P = qL

q = product of the charge

L = distance separating charges

Question 5

What is meant by dielectric behavior of a medium?

Answer 5

A strongly polar medium (high K) responds to an external electric field by reorienting its polar molecules so that the net electric field within the medium becomes weaker than the external field. (δ+ charges of the medium align with the negative plate and δ- charges align with the positive plate)

Question 6

Mass of an electron

Answer 6

9.11 x 10^-31 kg

Question 7

Diagram of electric field

Answer 7

Question 8

What is the net force on an electric dipole in a uniform electric field?

Answer 8

zero

Question 9

What are the units of electrical potential energy?

Answer 9

J

Question 10

Equation: change in electrical potential energy

Answer 10

ΔPEq = kq₁q₂ (1/r_f - 1/r_i)

r_i = initial separation of charges

r_f = final separation of charges

Question 11

Equation: magnetic field force

Answer 11

F_magnetic = qvB⊥ = qvBsinθ

v = velocity

B = magnetic field

θ = angle between v and B

Question 12

Equation: electrical potential difference of a moving charged particle (2 versions)

Answer 12

V_AB = ΔPE_AB/q

ΔPEq = qV

Question 13

When a charged particle moves with velocity through a magnetic field, at what position is the magnetic force strongest? Weakest?

Answer 13

velocity perpendicular to magnetic field: greatest force

volecity parallel to magnetic field: smallest force

Question 14

Equation: electric field

Answer 14

E = F/q = mg/q

Question 15

What is a conductor?

Answer 15

a material that allows for the movement of a charge

Question 16

What are equipotential lines? What is their positional relation to field lines?

Answer 16

They are lines that connect all points within an electric field sharing the same potential. They are perpendicular to field lines.

Question 17

What are the units of electrical potential energy difference?

Answer 17

J/C = volt (V)

Question 18

What is the unit of an electric field?

Answer 18

N/C

Question 19

What is an absolute potential?

Answer 19

Voltage measurements at points in space relative to the ground point.

Question 20

About how much greater is the mass of a proton than the mass of an electron?

Answer 20

~2000

Question 21

What are the units of magnetic fields?

Answer 21

N•s/C•m or N/A•m = T (tesla)

Question 22

Diagram of magnetic field

Answer 22

Question 23

What is Lenz’s law of conducting loops?

Answer 23

As a conducting loop enters a magnetic field, the loop experiences an induced current that creates a magnetic field in the opposite direction. When it is immersed in the field, it experiences no current. When it exits, it again creates a magnetic field, this time opposite the one it made.

Question 24

Equation: Coulomb’s law of electrical force

Answer 24

F = k (|q1q2|)/r²

k = proportionality constant = 8.99 x 10⁹ N•m²/C²

Question 25

Equation: torque on a conducting loop within a magnetic field

Answer 25

τ = *NIAB* sinφ N = # of turns I = current A = area of loop B = external magnetic field φ = angle between external field and loop's field

Question 26

Charge of an electron

Answer 26

-1.6 x 10^-19 C

Question 27

What is a solenoid?

Answer 27

a helical winding of a conducting wire wound on a cylindrical tube where the length is at least four times its radius Upon passing current through a solenoid, it can generate a linear magnetic field.

Question 28

Equation: torque of electric dipole in a uniform electric field (2 versions)

Answer 28

τ = (pE)(sinθ) = (qE)(Lsinθ) p = dipole

Question 29

Equation: dielectric constant

Answer 29

K = F_vacuum/F_medium

Question 30

Mass of a neutron

Answer 30

1.673 x 10^-27 kg

Question 31

When a test charge moves in the direction of a field line, it moves from higher/lower potential to higher/lower potential?

Answer 31

It moves from higher to lower potential.

Question 32

How can electrical potential energy between two charges be changed?

Answer 32

If you must do work to move two charges, you have increased their PE (bring two like charges together, pulling opposite charges apart). If the charges move naturally, they are decreasing their PE (bring two opposite charges together, pulling like charges apart).

Question 33

When a solenoid generates a mangetic field, what is that field dependent upon?

Answer 33

- current (I) passing through the solenoid - solenoid dimensions

Question 34

What is charge conservation?

Answer 34

The total electric charge on two objects in a system does not change. Even though the charge can be transferred from one object to the next, it cannot be created or destroyed.

Question 35

Charge of a proton

Answer 35

1.6 x 10^-19 C

Question 36

When an electric dipole (p) is introduced into a uniform electric field (E), at which position is its potential energy the greatest? the least?

Answer 36

dipole perpendicular to electric field: zero PE dipole parallel to electric field: most stable, negative PE dipole antiparallel to electric field: least stable, positive PE

Question 37

What are the units of charge?

Answer 37

coulomb (C)

Question 38

What is an insulator?

Answer 38

a material that impedes the movement of charge

Question 39

Equation: potential energy of electric dipole in a uniform electric field

Answer 39

PE = - (pEcosθ)

Question 40

Right-hand rule of magnetic force

Answer 40

thumb = velocity of positively charged particle fingers = direction of magnetic field palm = magnetic force \*If particle is negative, the force will be opposite

Question 41

Right-hand rule for current in magnetic field

Answer 41

Thumb = direction of magnetic field B Curled fingers = CW/CCW direction of current

Question 42

Mass of a proton

Answer 42

1.673 x 10^-27 kg

Question 43

How do equipotential lines correlate with work done on a test charge?

Answer 43

If the test charge is placed at any point along an equipotential line, the electric field does no work on that test charge.

Question 44

Equation: exit speed of a charged particle in a velocity selector

Answer 44

v = E/B

Question 45

Equation: mass spectrometer radius/mass correlation

Answer 45

r = mv/qB

Question 46

What is an electrical ground point?

Answer 46

An electrical point of reference with a voltage of 0.

Question 47

Diagram of symbols for magnetic field into or out of page

Answer 47

Question 48

When an electric dipole (p) is introduced into a uniform electric field (E), at which position is its torque the greatest? the least?

Answer 48

dipole perpendicular to field = greatest torque dipole parallel/antiparallel to field = least torque

Question 49

Equation: electric force in a field

Answer 49

F_electric = qE = mg

Question 50

Equation: electric work (2 versions)

Answer 50

W = qEΔd = qΔV

Question 51

Equation: velocity of charged particle in electric field

Answer 51

Vf = √(2qΔV/m)

Question 52

Equation: force on conducting loop in a magnetic field

Answer 52

F = I*l* x B I = current *l* = length of loop B = magnetic field

Question 53

Do electric fields and magnetic fields have the ability to accelerate a charged particle from rest?

Answer 53

Electric fields can, magnetic fields cannot.

Question 54

Do electric fields and magnetic fields do work on a charged particle?

Answer 54

Electric fields can, magnetic fields cannot.