Magnetism

Question 1

true or false; any breaks in a series circuit ceases the current to flow

Answer 1

true

Question 2

what is the equation for cost of electricity?

Answer 2

Cost = Power (kW) * time (hrs)* cost (cents/ kWh)

Question 3

Define magnetism

Answer 3

fundamental property of matter

• physical property of matter that causes certain materials to experience a force when near other magnets or magnetic fields
• magnetic materials : Fe, Ni, Co, neodymium

Question 4

What is a permanent magnet

Answer 4

object that displays persistent magnetism

Question 5

what are the two magnetic regions

Answer 5

south and north pole

Question 6

true or false; magnetic monopoles exist

Answer 6

false

- there is no such thing

Question 7

why don’t magnetic monopoles exist

Answer 7

when a magnet is cut in half; poles will re-establish themselves

Question 8

when do magnets experience a force

Answer 8

when around other magnets

Question 9

what are the fundamental laws of magnetism

Answer 9

like poles repel

opposite poles attract

Question 10

What is a magnetic force

Answer 10

mediated by a magnetic field

- surrounds a magnet (just like E-field surrounds a charge)

Question 11

what is the symbol for magnetic field

Answer 11

B

Question 12

true or false; magnetic field has a magnitude and direction

Answer 12

true

Question 13

Which direction do the arrows (field lines) go

Answer 13

north to south pole

Question 14

What are the units for magnetic fields

Answer 14

Tesla (T) = 10 000 Gauss (G)

Question 15

true or false; north pole is pushed along the field lines

Answer 15

true

Question 16

true or false; south pole is pushed along the field lines

Answer 16

false; south pole is pushed against the field lines

Question 17

true or false; a magnet put in an external magnetic field will attempt to align itself parallel to the field lines

Answer 17

true

Question 18

The Earth is like a big bar magnet. The north pole of a compass needle points towards North (North Canada to be precise). Where is the magnetic south pole of the Earth?

Answer 18

North Canada

- because north of a compass is attracted to south pole of the Earth

Question 19

what causes an electric charge

Answer 19

is the lack or excess of elementary electric charges (electrons)

Question 20

What did Oersted show?

Answer 20

that a current flowing through a wire can deflect a compass needle

Question 21

What was Oersted’s demonstration

Answer 21

he placed a magnetic needle beneath a current carrying wire

Question 22

true or false; an electric current produces a magnetic field

Answer 22

true

Question 23

What is current

Answer 23

the flow of electric charge

Question 24

what is the source of all magnetism

Answer 24

the movement of electric charge

Question 25

what are the 2 quantum mechanical contributions that describes an electrons movement

Answer 25

- electrons: spin angular momentum | - orbitals: orbital angular momentum

Question 26

what are electrons

Answer 26

fermions

Question 27

describe the characteristics of an electrons

Answer 27

- no two electrons have the exact same set of characteristics - only two electrons can fit inside a single box, and they must have opposite magnetic moments - if two electrons have the opposite magnetic moments they cancel

Question 28

true or false; unpaired electrons are required for a material to be magnetic

Answer 28

true

Question 29

true or false; if the magnetic moments of the atoms point to random directions they cancel

Answer 29

true

Question 30

What is the effect of an external magnetic field to randomly oriented atoms

Answer 30

they align parallel | - but when the field is turned off, the random orientation returns

Question 31

What is a ferromagnet

Answer 31

they want to align magnetic moments parallel

Question 32

define magnetic domain

Answer 32

region where the magnetic moments of atoms are aligned parallel

Question 33

If a weak external magnetic field is turned off, how does this affect the conductor?

Answer 33

thermal motion aligns the domains randomly after the field turned off

Question 34

if a strong external magnetic field is turned off, how does this affect the conductor?

Answer 34

domains stay aligned after the field is removed | - the material then becomes a permanent magnet

Question 35

What is another method to make a permanent magnet?

Answer 35

stroke a piece of iron with magnet to align all the domains

Question 36

Why does dropping or heating the magnet cause the domains to weaken?

Answer 36

domains can jostle out of alignment

Question 37

what is an electromagnet?

Answer 37

type of magnet in which the magnetic field is produced by the flow of electric current - stopping current stops magnetism

Question 38

What is a current loop

Answer 38

produces a magnetic field concentrated in the center of the loop, pointing away or towards the screen

Question 39

true or false; a strong magnetic field can be generated by winding a wire into a coil

Answer 39

true, called a solenoid

Question 40

when does a solenoid act as a magnet

Answer 40

only when current is flowing

Question 41

true or false; stationary charge in a static magnetic field experiences no net force

Answer 41

true - will not be moved to any direction - align along the magnetic field

Question 42

true or false; moving charge does not experience a force, in the magnetic field

Answer 42

false; it does experience a force | - force is perpendicular to the magnetic field and to the direction of charge motion

Question 43

What does F stand for?

Answer 43

Force on a charge moving perpendicular to the magnetic field

Question 44

what is equation for finding the force on a charge moving perpendicular to to the magnetic field?

Answer 44

F= q*v* B q: charge v: speed B: magnetic field magnitude (T)

Question 45

true or false; if there is no current there is no movement of charge and hence no force on the wire

Answer 45

true

Question 46

what does current flowing mean

Answer 46

it means that charges experience the Lorentz force

Question 47

what is the equation for Lorentz force

Answer 47

F= I* L* B I: current L: length (m) B: magnitude of magnetic field

Question 48

What is electromagnetic induction

Answer 48

changing a magnetic field can give rise to an electric current in a conducting wire (discovered by Micheal Faraday and Joseph Henry independently in 1831)

Question 49

What can the changing magnetic field be realized by

Answer 49

a moving magnet | - or a moving conductor in a static magnetic field

Question 50

what happens eg.a moving magnet, is realized by a changing magnetic field

Answer 50

voltage is caused or induced across the conductor - which results in the flow of current - even without any battery connected

Question 51

what does Faraday's law state?

Answer 51

-the greater the number of loops of wire that move in a magnetic field, the greater the induced voltage

Question 52

true or false; you can create electrical energy from nothing by simply moving a magnet

Answer 52

false | it is not possible

Question 53

what does Lentz law state

Answer 53

- The induced voltage gives rise to a current. Currents always give rise to a magnetic field - the poles of the induced magnetic field are always such that they oppose the movement of the magnet - therefore there is a repulsive force one must overcome to move the magnet through the coil - this means mechanical work is required

Question 54

true or false; electromagnetic induction allows mechanical energy to be transformed into electrical energy

Answer 54

true

Question 55

What is a generator

Answer 55

a simple apparatus in which coil is rotated in a static magnetic field mechanical energy is converted into electrical energy

Question 56

What happens when the string of an electrical guitar is plucked?

Answer 56

its vibration will perturb the magnetic field of the magnet. This induces a current in a coil on the pickup. The electrical signal is transmitted to an amplifier and sent to the speakers