Test 3

Question 1

ampere’s law

Answer 1

the physical law that states that the magnetic fiel around an electric current is proportional to the current; each segment of current produces a magnetic fiel like that of a long straight wire, and the total field of any shape current is the vector sum of the fields due to each segment

Question 2

B-field

Answer 2

another term for magnetic field

Question 3

Biot-Savart Law

Answer 3

a physical law that describes the magnetic field generated by an electric current in terms of a specific equation

Question 4

Curie temperature

Answer 4

the temperature above which a ferromagnetic material cannot be magnetized

Question 5

direction of magnetic field lines

Answer 5

the direction that the north end of a compass needle points

Question 6

domains

Answer 6

regions within a material that behave like small bar magnets

Question 7

electromagnet

Answer 7

an object that is temporarily magnetic when an electrical current is passed through it

Question 8

electromagnetism

Answer 8

the use of electrical currents to induce magnetism

Question 9

ferromagnetic

Answer 9

materials, such as iron, cobalt, nickel, and gadolinium, that exhibit strong magnetic effects

Question 10

gauss

Answer 10

G, the unit of the magnetic field strength: 1 G= 10^-4 T

Question 11

hall effect

Answer 11

the creation of voltage across a current-carrying conductor by a magnetic field

Question 12

Hall emf

Answer 12

the electromotive force created by a current-carrying conductor by a magnetic field: (epsilon)=Blv

Question 13

Lorentz force

Answer 13

the force on a charge moving in a magnetic field

Question 14

magnetic field

Answer 14

the representation of magnetic forces

Question 15

magnetic field lines

Answer 15

the pictorial representation of the strength and the direction of a magnetic field

Question 16

Magnetic field strength (magnitude) produced by a long straight current-carrying wire:

Answer 16

B=(permeability of free space)I/2pi*r

r= shortest distance to the wire

Question 17

Magnetic field strength at the center of a circular loop

Answer 17

B=(permeability of free space)*I/2R

R is defined as the radius of the loop

Question 18

Magnetic field inside of a solenoid

Answer 18

B=(permeability of free space)In

n= # of loops per unit length of the solenoid (N/l)

Question 19

Magnetic force

Answer 19

the force on a charge produced by its motion through a magnetic field; the Lorentz force

Question 20

magnetic monopoles

Answer 20

an isolated magnetic pole; a South Pole without a North Pole and vice versa. No monopole has been observed

Question 21

Maxwell’s equations

Answer 21

a set of four equations that describe electromagnetic phenomena

Question 22

meter

Answer 22

common application of magnetic torque on a current-carrying loop that is very similar in construction to a motor; by design, the torque is proportional to I and not (theta), so the needle deflection is proportional to the current

Question 23

motor

Answer 23

loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process

Question 24

north magnetic pole

Answer 24

the end or the side of a magnet that is attracted to the Earth’s geographic north pole

Question 25

Permeability of free space

Answer 25

the measure of the ability of a material, in this case free space, to support a magnetic field; the constant (mu naught)= 4*pi*10^-7

Question 26

Right hand rule 1

Answer 26

the rule to determine the direction of the magnetic force on a positive moving charge: when the thumb of the right hand points in the direction of the charge's velocity v and the fingers point in the direction of the magnetic field B, then the force on the charge is perpendicular and away from the palm; the force on a negative charge is perpendicular and into the palm

Question 27

right hand rule 2

Answer 27

A rule to determine the direction of the magnetic force induced by a current-carrying wire: point the thumb of the right hand in the direction of the current, and the fingers curl in the direction of the magnetic field loops

Question 28

solenoid

Answer 28

a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it

Question 29

south magnetic pole

Answer 29

the end or the side of a magnet that is attracted toward Earth's geographic South Pole

Question 30

Tesla

Answer 30

T, the SI unit of the magnetic field strength; 1 T= 1N/ A*m

Question 31

Back emf

Answer 31

the emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor

Question 32

Capacitative reactance

Answer 32

the opposition of a capacitor to a change in current; calculated by Xc=1/2*pi*f*C

Question 33

Characteristic time constant

Answer 33

``` denoted by (tau), a particular series RL circuit is calculated by (tau)=L/R L= inductance R= resistance ```

Question 34

eddy current

Answer 34

a current loop in a conductor caused by motional emf

Question 35

electric generator

Answer 35

a device for converting mechanical work into electric energy; it induces an emf by rotating a coil in a magnetic field

Question 36

Electromagnetic induction

Answer 36

the process of inducing an emf (voltage) with a change in magnetic flux

Question 37

Emf induced in a generator coil

Answer 37

``` emf= NAB(w*) sin(w*t) A= area of an N-turn coil rotated at a constant angular velocity w* in a uniform magnetic field B, over a period of time t ```

Question 38

Energy stored in an inductor

Answer 38

self explanatory; calculated by E(ind)=.5*L*I^2 | I= current

Question 39

Faraday's law of induction

Answer 39

the means of calculating the emf in a coil due to changing magnetic flux, given by emf= -N (change in phi)/ (change in time)

Question 40

Henry

Answer 40

unit of inductance; 1 H= 1 ohm * s

Question 41

inductance

Answer 41

a property of a device describing how efficient it is at inducing emfs in another device

Question 42

induction

Answer 42

(magnetic induction) the creation of emfs and hence currents by magnetic fields

Question 43

inductive reactance

Answer 43

the opposition of an inductor to a change in current | X(L)= 2 * pi * f * L

Question 44

inductor

Answer 44

a device that exhibits significant self-inductance

Question 45

Lenz's law

Answer 45

the minus sign in Faraday's law, signifying that the emf induced in a coil opposes the change in magnetic flux

Question 46

magnetic damping

Answer 46

the drag produced by eddy currents

Question 47

magnetic flux

Answer 47

``` denoted by (phi), the amount of magnetic field going through particular area, calculated with (phi)=BAcos(theta) B= magnetic field strength A= area (theta)= angle with the perpendicular to the area ```

Question 48

Mutual inductance

Answer 48

how effective a pair of devices are at inducing emfs in each other

Question 49

peak emf

Answer 49

emf (naught)= NAB(w*)

Question 50

Phase angle

Answer 50

denoted by ø, the amount by which the voltage and current are out of phase with each other in a circuit

Question 51

self inductance

Answer 51

how effective a drive is at inducing emf in itself

Question 52

step-down transformer

Answer 52

a transformer that decreases voltage

Question 53

step-up transformer

Answer 53

a transformer that increases voltage

Question 54

transformer

Answer 54

a device that transforms voltages from one value to another using induction

Question 55

transformer equation

Answer 55

the equation showing that the ratio of the secondary to primary voltage in a transformer equals the ratio of the # of loops in their coils; V(s)/V(p)=N(s)/N(p)