Electromagnetism

Question 1

what is a magnetic field

Answer 1

a region in which forces are exerted on magnetic poles/currents

Question 2

what are the magnetic elements

Answer 2

iron,cobalt,nickel

Question 3

what happens to 2 like poles

Answer 3

they repel

Question 4

what happens to 2 unlike poles

Answer 4

they attract

Question 5

explain the right hand thumb rule

Answer 5

this

Question 6

how can a wire’s m.f be increased

Answer 6

by wrapping it in a coil called a solenoid
can also use a soft iron core to make an induced magnet

Question 7

what is an electromagnet

Answer 7

when the current stops, so the m.f also stops

Question 8

what is fleming’s left hand rule

Answer 8

this

Question 9

what is the anagram to remember the left hand rule

Answer 9

FBI

Question 10

what is an induced magnet

Answer 10

a material that becomes a magnet when placed in a magnetic field

Question 11

what happens to an induced magnet when removed from the magnetic field

Answer 11

the induced magnet loses most/all of its magnetism quickly

Question 12

what is a magnetic field

Answer 12

the region around a magnet where a force acts on a magnetic material

Question 12

how is a magnetic field produced

Answer 12

if current flows through a wire, a magnetic field is produced around it

Question 13

describe the m.f inside a solenoid

Answer 13

strong+uniform

Question 14

what is the motor effect

Answer 14

when a current-carrying conductor is placed in a m.f, the magnet producing a field and the conductor exert a force on each other

Question 15

what is force= in terms of magnetic flux density, current and length

Answer 15

F= magnetic flux density x current x length

Question 16

what appliances use the motor effect

Answer 16

loudspeakers and headphones

Question 17

What is the generator effect

Answer 17

-if an electrical conductor moves relative to a m.f or if there is a change in the m.f around a conductor, a p.d is induced across the conductor.
-if the conductor is part of a complete circuit, a current is induced in the conductor

Question 18

how is generator effect used for d.c, a.c devices

Answer 18

used in alternator to make a.c
used in dynamo to make d.c

Question 19

how do microphones use the generator effect

Answer 19

to convert the pressure variations in sound waves into variations in current in electrical circuits

Question 20

what does a transformer do

Answer 20

it changes the p.d and current of an a.c.This is used as we want ti reduce currents for transmission over long distances to decrease energy lost

Question 21

How does a transformer work

Answer 21

an alternating current is passed through the primary coil, this creates an alternating m.f.The alternating m.f will induce an alternating p.d in the secondary coil. If the circuit is complete, an a.c is passed through the secondary coil

Question 22

how is the number of coils + p.d linked in a transformer

Answer 22

Vp/Vs= Np/Ns

Question 23

how is power linked in the primary and secondary coil

Answer 23

Pp=Ps

Question 24

what does the split-ring commutator do

Answer 24

allows d.c to be produced

Question 25

Electromagnets in a bell/fire bell

Answer 25

-current passes through the coil, magnetic field is created around the electromagnet -the iron armature is attracted by the electromagnet, and the bell will be rung, breaking the circuit -the armature bounces off the bell, closing the circuit

Question 26

electromagnets in a relay

Answer 26

-current passes through the coil, magnetic field is created around the electromagnet -iron armature is attracted to the EM and rotates -the armature pushes the switch gap together-completing the circuit

Question 27

electromagnetic switch

Answer 27

-current passed through the coil, a m.f is created around the electromagnet/solenoid -field attracts the switch towards the electromagnet -breaks the circuit

Question 28

what are the 4 components in a simple alternator

Answer 28

permanent magnet,rotating coil,slip-rings, carbon brushes

Question 29

what does permanent magnet do

Answer 29

provides a uniform m.f

Question 30

what does rotating coil do

Answer 30

cuts the m.f as it rotates and allows an induced current to flow

Question 31

slip-rings

Answer 31

allows the alternating current to flow between the coil and external circuit

Question 32

carbon brushes

Answer 32

provides a good electrical connection between a coil and external circuit

Question 33

how can an induced p.d be measured

Answer 33

can be measured with a galvanometer connected to the external circuit

Question 34

how is a p.d induced in the alternator

Answer 34

as the coil cuts the m.f lines with the rotations, when its upright

Question 35

when is the max p.d induced

Answer 35

when the position of the coil is horizontal when the motion of the coil is perpendicular to the field

Question 36

what is a dynamo

Answer 36

a device that converts electrical input into motion, d.c motor

Question 37

what does a split-ring commutator do

Answer 37

changes the connection between the coil and brushes every half turn- to keep current leaving the dynamo in the same direction -happens every time the coil is perpendicular to the m.f lines