Chapter 23

Question 1

an electric current is set up in the coil as long as _______ occurs between the magnet and the coil

this current is called an _______, and it is produced by an _______

Answer 1

relative motion

induced current
induced emf

Question 2

a current exists in a wire even though no _______ are connected to the wire

Answer 2

batteries

Question 3

electric current can be produced by a time-varying _______

Answer 3

magnetic field

Question 4

an emf is induced in a circuit when the _______ through the surface bounded by the circuit changes with _______

Answer 4

magnetic flux

time

Question 5

the emf induced in a circuit is _______ to the time rate of change of magnetic flux through the circuit

Answer 5

equal

Question 6

the loops are in _______, so the emfs in the individual loops add to give the total emf

Answer 6

series

Question 7

an emf can be INDUCED in a circuit by changing the MAGNETIC FLUX in several ways:

1) the magnitude of the magnetic field can _______
2) the _______ of the circuit can change with time
3) the _______ between the field and the normal to the loop can change with time
4) any combination of these changes can occur

Answer 7

vary with time
area
angle, theta

Question 8

a _______ is one induced in a conductor moving through a magnetic field

Answer 8

motional emf

Question 9

in motional emf, the charges accumulate at _______ of the conductor until they are in _______ with regard to the electric and mag forces

Answer 9

both ends

equilibrium

Question 10

a _______ is maintained in motional emf as long as the conductor is moving through the mag field

if the motion is reversed, the polarity of the value is also _______

Answer 10

potential

reversed

Question 11

from an energy standpoint in motional emf:

• the applied force _______ on the conducting bar
• this _______ the charges through a mag field
• the change in energy of the system during some time interval must be _______ to the transfer of energy into the system by work

Answer 11

does work
moves
equal

Question 12

the power input in motional emf is equal to the rate at which energy is _______

Answer 12

delivered to the resistor

Question 13

_______ is a device in which energy is transferred in by work and out by electrical transmission, consists of a coil of wire rotated in a external magnetic field by some external agent, which represents the work input

Answer 13

AC generator

Question 14

_______ is a device in which energy is transferred in by work and out by electrical transmission, consists of a coil of wire rotated in a external magnetic field by some external agent, which represents the work input

Answer 14

AC generator

Question 15

maximum emf occurs when wt = _______ or _______, which is called _______

Answer 15

90
270
ac voltage

Question 16

the induced current in a loop is in the direction that _______ that opposes the change in _______ through the area enclosed by the loop

Answer 16

creates

magnetic flux

Question 17

the induced current tends to keep the original magnetic flux through the loop from _______

Answer 17

changing

Question 18

consider a conducting loop in a uniform mag field
if the field changes with time, an emf is _______ in the loop

an electric field has to _______ in order to provide an electric force on the charges around the loop

Answer 18

induced

tangent to the loop

Question 19

the _______ by the electric field on the loop in moving a test charge q _______ around the loop is equal to W = qe

Answer 19

work done

once

Question 20

the induced electric field is a _______ that is generated by a changing mag field, because the work done in moving a charge around a closed path is not _______

this type of electric field is very different from an _______

Answer 20

nonconservative field
zero

electrostatic field

Question 21

as the current increases with time, the magnetic flux through the circuit loop due to this current _______

Answer 21

also increases with time

Question 22

increasing flux creates an _______ in the circuit (also called _______)

Answer 22

induced emf

back emf

Question 23

this induced emf (from an induced flux by an induced current) _______ the change in the new magnetic flux through the loop of the circuit

Answer 23

opposes

Question 24

by lenz’s law, the induced electric field in the wires must be _______

Answer 24

opposite of the direction of the current

Question 25

the direction of the _______ is such that it would cause an induced current in the loop which would establish a magnetic field _______

Answer 25

induced emf | opposing the change in the original magnetic field

Question 26

the direction of the induced emf (back emf) is _______ the direction of the emf of the battery this results in a gradual increase in the current to its final equilibrium value

Answer 26

opposite

Question 27

this effect is called _______ because the changing flux through the circuit and the resultant induced emf arise from the circuit itself the emf is called a _______

Answer 27

self-induction self-induced emf

Question 28

this effect is called _______ because the changing flux through the circuit and the resultant induced emf arise from the circuit itself the emf is called a _______

Answer 28

self-induction self-induced emf

Question 29

inductance, L, depends on the _______ of the coil and other _______

Answer 29

geometry | physical characteristics

Question 30

the inductance is a measure of the opposite to a _______ in current

Answer 30

change

Question 31

if a circuit contains a coil (solenoid), the inductance of the coil prevents the current in the circuit from _______ or _______

Answer 31

increasing | decreasing simultaneously

Question 32

a circuit element that has a large self-inductance is called an _______

Answer 32

inductor

Question 33

without a coil, a circuit will have some _______

Answer 33

self-inductance

Question 34

an RL circuit contains an _______ and a _______

Answer 34

inductor | resistor

Question 35

the inductor affects the current _______

Answer 35

exponentially

Question 36

if there is no inductor, the exponential term goes to zero and the current would instanteously reach its _______

Answer 36

maximum value

Question 37

the equilibrium value of the maximum current in an RL circuit is e/R and is reached as _______

Answer 37

t approaches infinitely

Question 38

the time rate of change of the current in an RL circuit is a maximum at _______ falls of exponentially as t approaches _______

Answer 38

t = 0 infinity

Question 39

when the inductor is present, it _______ in the current and causes the current to _______

Answer 39

opposes the decrease | exponentially

Question 40

in a circuit WITH an inductor, the battery must supply _______ than in a circuit WIHOUT an inductor - part of energy appears as _______ - remaining energy is stored in _______ of the inductor

Answer 40

more energy internal energy in the resistor magnetic field

Question 41

energy must therefore have been stored in the _______ and is now being delivered to the resistor

Answer 41

inductor

Question 42

the magnetic energy density equation is valid for any region of space in which a _______ exists

Answer 42

magnetic field

Question 43

_______ is a treatment for severe depression, in which _______ are induced in a patient under anesthesia

Answer 43

``` electroconvulsive therapy (ECT seizures ```

Question 44

_______ is a treatment for severe depression, in which _______ are induced in a patient under anesthesia

Answer 44

``` electroconvulsive therapy (ECT seizures ```

Question 45

_______ induces currents in the brain by means of magnetic induction rather than by the application of a large voltage from contact electrodes

Answer 45

transcranial magnetic stimulation (TMS)

Question 46

in TMS, an alternating current is passed through the coil, creating an _______, which induces _______ in the nerve cells of the brain

Answer 46

oscillating mag field | currents