p15 - electromagnetism

Question 1

define a permanent magnet

Answer 1

• a magnet that always has its own magnetic field
• attracts magnetic materials and can attracts or repel other magnets

Question 2

define an induced magnet

Answer 2

• temporary magnet made by putting a suitable material into a magnetic field
• alway an attractive force

Question 3

define poles in a magnet

Answer 3

• ends of a magnet
• names north and south based on which way on earth they’d point if suspended freely

Question 4

define magnetic field

Answer 4

• region around a magnet where a force acts on other magnets or magnetic materials (they are 3D unlike diagrams show)

Question 5

define magnetic compass

Answer 5

• a small bar magnet balanced on a pin so it can spin around
• point’s towards earth’s magnetic north due to earth’s magnetic field but can still be used to find direction of a magnetic field for another magnet

Question 6

where are magnetic forces the strongest?

Answer 6

poles of a magnet because here the magnetic field lines are the most concentrated

Question 7

what happens when magnets are brought together?

Answer 7

• a non contact force
• like poles repel
• unlike poles attract

Question 8

name the 4 magentic materials

Answer 8

1) iron
2) cobalt
3) steel
4) nickel

Question 9

how is induced magnetism quickly lost?

Answer 9

if the material is moved from the magnetic field that induced it

Question 10

what’s the direction of the magnetic field?

Answer 10

north to south

Question 11

define a ‘north seeking pole’?

Answer 11

• sometimes the north pole is referred to as this
• because it will point north on Earth if left freely suspended

Question 12

how can you find direction on a magnetic field?

Answer 12

by using a plotting compass

Question 13

which part of earth is magnetic?

Answer 13

• the core because a compass at the north pole would point down

Question 14

what is the difference between geographic north and magnetic north?

Answer 14

• geographic north is a fixed point
• magnetic north is the direction that a compass needle points to as it aligns with the earth’s magnetic field (respons to changes in earths core so is not fixed)

Question 15

define current

Answer 15

• rate of flow of charges in a circuit
• if a current if flowing in a component, electrons are flowing through it
• a wire that has a current also has an electric field

Question 16

define a solenoid

Answer 16

a coil of wire

Question 17

define an iron core

Answer 17

a piece of iron placed in the middle of a solenoid

Question 18

define an electromagnet

Answer 18

a coil of wire wth an iron core

Question 19

what happens when you switch the direction of the current?

Answer 19

the direction of the magnetic field also switches

Question 20

how can you increase the strength of a magnetic field?

Answer 20

• increase the current
• winding wire into coils/increasing coils
• from here you can put an iron core to increase even more, this creates an electromagnet

Question 21

how do you make an electromagnet stronger?

Answer 21

• increasing current in wire
• increasing length of wire in solenoid

Question 22

what is a good example of an iron core?

Answer 22

• in schools an iron nail could be used

Question 23

define ‘the motor effect’

Answer 23

a wire carrying a current creates a magnetic field. this can interact with another magnetic field, causing a force that pushes the wire at right angles.

Question 24

define ‘magnetic flux density’

Answer 24

• a measure of the strength of a magnetic field
• number of magnetic field lines going through a set area

Question 25

define an electric motor

Answer 25

a device that causes rotation of a coil of wire carrying a current when placed in a magnetic field

Question 26

give an equation relating to magnetic flux density

Answer 26

F (N) = B I L
force = magnetic flux density (tesla, T) x current (A) x length (m)

Question 27

how can you work out direction of force (when you know d of current and magnetic field)

Answer 27

• use fleming’s left hand rule
• force = thumb (both have 5 letters)
• magnetic Field = First finger
• Current = seCond finger

Question 28

how do you increase the size of the force on a conductor?

Answer 28

• increasing the current
• increasing length of wire
• incresing magnetic field strength

Question 29

what does the communtator do in the motor effect practical?

Answer 29

prevent wires from tangling up