Magnetism and Electromagnetism

Question 1

what is a magnetic field

Answer 1

the region of space around a magnet where a magnetic material will experience a force

Question 2

where is the magnetic field of a magnet strongest

Answer 2

at the poles

Question 3

in which direction do magnetic field lines always point

Answer 3

north to south

Question 4

what does the distance between magnetic field lines indicate

Answer 4

strength of the field, closer together = stronger field

Question 5

what is a permanent magnet

Answer 5

material that produces its own magnetic field

Question 6

what is an induced magnet

Answer 6

material that becomes magnetic when is put in a magnetic field

Question 7

what does a magnetic compass contain

Answer 7

small bar magnet

Question 8

what is produced around a wire when an electric current flows through it

Answer 8

magnetic field

Question 9

what factors does the strength of the magnetic field around a straight wire depend upon

Answer 9

size of current, distance from wire

Question 10

what effect does shaping the wire into a solenoid have on the magnetic field strength

Answer 10

increases strength of magnetic field

Question 11

how can the strength of the magnetic field inside a solenoid be increased

Answer 11

put an iron core inside

Question 12

what does Flemmings left hand rule show

Answer 12

relative orientation of the force, current in the conductor, and magnetic field for the motor effect

Question 13

what is magnetic flux density measured in

Answer 13

Tesla

Question 14

what is the motor effect

Answer 14

when a conductor placed in a magnetic field experiences a force

Question 15

what causes the motor effect

Answer 15

interaction between the magnetic field created by current in a wire and the magnetic field in which he wire is placed

Question 16

what do loudspeakers and headphones do

Answer 16

use the motor effect to convert variations in current in electrical circuits to pressure variations in sound waves

Question 17

2 ways that a p.d is induced in a conductor

Answer 17

• conductor moving relative to a magnetic field
• magnetic field around conductor changing

Question 18

what is another name for the generator effect

Answer 18

electromagnetic induction

Question 19

how can the direction of an induced p.d or current be reversed

Answer 19

• reverse movement of the conductor or magnet
• reverse polarity of the magnet

Question 20

what affects the size of an induced p.d or current

Answer 20

• speed of movement
• strength of the magnetic field
• number of turns in the coil

Question 21

how does an alternator make use of the generator effect

Answer 21

produces alternating current

Question 22

which kind of current is produced buy the generator effect in a dynamo

Answer 22

direct current

Question 23

how does a dynamo keep the current flowing in the same direction

Answer 23

a split ring commutator makes the ends of the coil swap contacts with the circuit every half turn

Question 24

when is the induced p.d produced by an alternator at its maximum

Answer 24

when the plane of the coil lies parallel to magnetic field lines

Question 25

how does a microphone use the generator effect

Answer 25

converts pressure variations in sound waves into variations in electrical current

Question 26

what does a transformer do

Answer 26

changes magnitude of the alternating p.d

Question 27

what does a basic transformer consist of

Answer 27

two coils of wire wound around an iron core

Question 28

why is iron used for the core of a transformer

Answer 28

iron is easily magnetised and demagnetised

Question 29

how does a transformer work

Answer 29

alternating p.d across the primary coil produces an alternating magnetic field in the iron core which induces an alternating p.d in the secondary coil

Question 30

which type of transformer has more turns on its secondary coil than its primary coil

Answer 30

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