magnetism (combined science)

Question 1

• what are the two types of magnetic poles

Answer 1

there are two types of magnetic pole: a north pole and south pole

Question 2

• what are the poles

Answer 2

the poles of a magnet are the places where the magnetic forces are strongest

Question 3

• what poles attract

Answer 3

poles attract the opposite. for example the north pole of a magnet will attract the south pole of another magnets south pole

Question 4

• what is the magnetic field

Answer 4

the region around a magnet, where a force acts on another magnet or magnetic material is called the magnetic field

Question 5

• what does the strength of the field depend on

Answer 5

the strength of the field depends on the distance from the magnet- it is strangest at the poles

Question 6

• what do permanent magnets do

Answer 6

permanent magnets produce their own magnetic field

Question 7

• what are induced magnets

Answer 7

induced magnets become a magnet when placed in a magnetic field. when removed from a magnetic field they lose their magnetism quickly

Question 8

• what is the force between magnets

Answer 8

the force between a permeant magnet and a magnetic material or an induced magnet is always one of attraction

Question 9

• what do the arrows on field lines do

Answer 9

the arrows on feild lines always run from north to south and show the direction of the force that would act on a north pole placed at that point

Question 10

• what is the density of field lines called and what odes it indicate

Answer 10

the density of field lines is called the flux density and indicates the strength of the field at that point - the closer together the lines, the higher the flux density

Question 11

• what happens when the flux density is higher

Answer 11

when the flux density is higher the field is stronger which means the greater the force that would be felt by another magnet

Question 12

• describe a magnetic compass

Answer 12

a magnetic compass contains a small bar magnet the compass needle aligns with the earth magnetic field and always points to the magnetic north

Question 13

• what does a magnetic compass do

Answer 13

it provides evidence that the earth’s core must be magnetic

Question 14

how do we plot feilds

Answer 14

place a bar magnet on a piece of paper

place a compass at one end of the magnet

on the paper, mark where the point of the needle is

move the compass so the tail of the needle is at the point that has just been marked

on the paper, mark a new point where the needle is

repeat and connect the marks until the full field is plotted

Question 15

how is a magnetic field produced around a wore

Answer 15

whenever a current flows in a conducting wire a magnetic field is produced around the wire

Question 16

what does the direction of field lines in an electromagnet depend on

Answer 16

the direction of the field lines depends on the direction of the current and can be found with the right hand grip method

Question 17

describe the right hand grip method

Answer 17

grip the wire in your right hand, with the thumb pointing in the direction of the current

the fingers curled around the wire will point in the direction that the field lines should be drawn

Question 18

what does the strength of an electromagnetic field depend on

Answer 18

the strength of the field depends on the size of the current and the distance from the wire

Question 19

how can we see the effect of distance and current

Answer 19

this effect can be seen by placing a magnetic compass at different points along the wire and turning the power supply on and off

Question 20

when is a solenoid formed

Answer 20

a solenoid is formed when a wire is looped into a cylindrical coil

Question 21

how do we increase the strength of a magnetic field

Answer 21

shaping the wire into a solenoid increases the strength of the magnetic field, creating a strong uniform field inside the solenoid

to increase the field strength further, an iron core can be added this creates an electromagnet

Question 22

the solenoid increases the magnetic field because…

Answer 22

it concentrates a longer piece of wire into a smaller area

the looped shape means that the magnetic field lines around the wire are all in the same direction

Question 23

what is the magnetic field like around a solenoid

Answer 23

the magnetic field around a solenoid has a similar shape to that around a bar magnet

Question 24

describe how we find the north pole of a solenoid

Answer 24

the north pole of a solenoid can be found with the right-hand grip method

hold the solenoid in your right hand with your fingers following the direction the current flows

your thumb will point to the north pole of the solenoid

Question 25

how does an electric bell work

Answer 25

when the switch is pushed, the electromagnet is magnetized

the electromagnet attracts the armature

the hammer strikes the gong and breaks the circuit

the armature springs back, completing a circuit again and remagnetizing the electromagnet

the cycle repeats for as long as the button remains pushed