magnetism and electromagnetism

Question 1

at which part of a magnet are the magnetic forces stronger

Answer 1

the poles of the magnet

Question 2

what happens when two magnets are brought close to each other

Answer 2

the exert a force on each other

Question 3

what type of force is exerted if two like poles of a magnet are brought near each other

Answer 3

a repulsive
non-contact force

Question 4

what type of force is exerted if two unlike poles of a magnet are brought near each other

Answer 4

an attractive
non-contact force

Question 5

what is the difference between a permanent magnet and an induced magnet

Answer 5

a permanent magnet produces its own magnetic field
an induced magnet becomes magnetic when placed in a magnetic field

Question 6

what type of force does induced magnetism always cause

Answer 6

a force of attraction

Question 7

what happens when an induced magnet is removed from a magnetic field

Answer 7

the induced magnet loses most/all of its magnetism

Question 8

what is a magnetic field

Answer 8

the region surrounding a magnet where another magnet or magnetic material experiences a non-contact force

Question 9

give 4 examples of magnetic materials

Answer 9

1. iron
2. steel
3. cobalt
4. nickle

Question 10

what can always be said about the force between a magnet and magnetic materials

Answer 10

it is always attractive

Question 11

how does the stength of a magnetic field alter as you move further away from the magnet producing it

Answer 11

the magnetic field strength decreases the further you move away

Question 12

in which direction does a magnetic field point

Answer 12

in the direction that a North Pole would experience a force is placed in the field
from the north seeking pole to the south seeking pole of a magnet

Question 13

what does a magnet compass contain

Answer 13

a small bar magnet that points in the direction of the earths magnetic field

Question 14

what is produced when current flows through a conducting wire

Answer 14

a magnetic field is produced around the wire

Question 15

what determines the strength of the magnetic field around a current carrying wire

Answer 15

the magnitude of the current flowing through the wire
the distance from the wire

Question 16

what is a solenoid

Answer 16

a coil of wire which when current passes through creates a strong magnetic field

Question 17

describe the magnetic field found inside a solenoid

Answer 17

strong and uniform

Question 18

what is an electromagnet

Answer 18

a solenoid with an added iron core
adding the iron core increase the strength of the magnetic field

Question 19

what is the motor effect

Answer 19

when a force is exerted between a magnetic field and a current carrying conductor placed in that field

Question 20

what rule is used to determine the force experiences due to the motor effect

Answer 20

flemings left-hand rule

Question 21

when using flemings left hand rule what does the forefinger represent

Answer 21

the forefinger points in the direction of the magnetic field

Question 22

when using flemings land hand rule what does the second finger represent

Answer 22

the 2nd finger points in the direction of current flow in the conductor

Question 23

what factors affect the size of the force on a current-carrying wire in a magnetic field

Answer 23

the magnitude of the current flowing through a conductor
the strength of the magnetic field that the conductor is placed in

Question 24

if the direction of current in a current carrying wire is placed in a uniform magnetic field is reversed, what happens to the force

Answer 24

the direction of the force is reversed

Question 25

if the strength of the current in a current carrying wire placed in a uniform magnetic field is increased, what happens to the force?

Answer 25

the strength of the force is increased

Question 26

what criteria must be met for the equation linking force, magnetic flux density, current and length to hold

Answer 26

the conductor must be at right-angles to the magnetic field it is placed in

Question 27

what is the unit for magnetic flux density

Answer 27

Tesla T

Question 28

how does an electric motor work

Answer 28

a coil of wire, carrying a current, is placed in a magnetic field
the forces on the two sides perpendicular to the field experience forces in opposite directions
this causes a rotational effect

Question 29

how do loudspeakers make use of the motor effect

Answer 29

the motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound

Question 30

explain how a loudspeaker works

Answer 30

a cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
when current flows through the wire, it creates a second magnetic field, which interacts with the permanent field
this produces a force which causes the cone to vibrate

Question 31

how is the pitch of the sound form a loudspeaker changed

Answer 31

the frequency of the a.c current is altered
this creates a different frequency of vibration in the cone

Question 32

what happens when an electrical conductor moves relative to a magnetic field

Answer 32

a potential difference is induced across the ends of the conductor

Question 33

what happens to an electrical conductor when there is a change to the magnetic field that is placed in?

Answer 33

a potential difference is induced across the ends of the conductor

Question 34

what is the requirement for an induced potential difference to cause a current flow

Answer 34

the conductor must form a closed loop or be part of a complete circuit

Question 35

what can be said about the direction of the magnetic field produced by an induced current

Answer 35

the direction of the field is such that it imposes the change that induced the current
this change is either the movement of the conductor or a change to the field

Question 36

what are 2 ways that the generator effect is used to generate different types of current

Answer 36

in an alternating to produce alternating current
in a dynamo to produce direction current

Question 37

what electromagnetic effect does a microphone take advantage of and how

Answer 37

the generator effect
it converts the pressure variations in sound waves into alternating current in a circuit

Question 38

describe the makeup of a basic transformer
huh

Answer 38

a primary coil and a secondary coil of wire wrapped around a iron core

Question 39

why is iron used as the core for a transformer

Answer 39

it is easily magnetised

Question 40

explain how a transformer works

Answer 40

an alternating current flows through the primary coil
this induces a changing magnetic field in the core
this changing magnetic induces a current to flow in the secondary coil

Question 41

why must the current flowing through the primary coil of a transformer be alternating?

Answer 41

for current to be induced in the secondary coil, the magnetic field in the core must be continuously changing
for the magnetic field to be changing, the current in the primary coil must be alternating

Question 42

what can be said about the electrical power put and output of a 100% efficient transformer?

Answer 42

the electrical power input is equal to the electrical power output