magnetism and electromagnetism ✓

Question 1

what are the SI units for current ?

Answer 1

Amps - A

Question 2

what are the SI units for voltage ?

Answer 2

volts - v

Question 3

what are the SI units for power ?

Answer 3

Watts - W

Question 4

magnets with the same poles do what ?

Answer 4

repel each other

Question 5

magnets with the opposite poles do what ?

Answer 5

attract each other

Question 6

which are the three materials that can be magnetised ?

Answer 6

Nickel
Iron
Cobalt

Question 7

what are the links to the materials that can be magnetised meaning that something else relating to them can be magnetised ?

Answer 7

their alloys eg steel

Question 8

what is a material that can be temporarily magnetised called ?

Answer 8

magnetically soft

Question 9

what is a material that can be permanently magnetised called ?

Answer 9

magnetically hard

Question 10

what do magnetic field lines show ?

Answer 10

the direction of the magnetic field from north to south

Question 11

what is an experiment to investigate the magnetic field pattern around a bar magnet ?

Answer 11

• get bar magnet
• put piece of paper over top of bar magnet
• pour some iron filing over the bar magnet in all directions
• iron filings show the strength and shape of magnetic field

Question 12

what is produced when an electric current is put in a conductor ?

Answer 12

produces a magnetic field around it

Question 13

how is an electromagnet constructed ?

Answer 13

when an electric current flows into the wire and creates a magnetic field around the wire

Question 14

how do you increase the strength of an electromagnet ?

Answer 14

• larger current
• adding more coils
• adding an iron core

Question 15

what is the motor effect ?

Answer 15

• current flows in a conductor (wire or coil)
• this creates a magnetic field around the wire, which interacts with the permanent magnetic field
• This creates a force (movement) on the wire
• (For a motor, this creates an upwards force on one side, and a downwards force on the other side)

Question 16

what does the first finger of flemming’s left hand rule show ?

Answer 16

magnetic field (N-S)

Question 17

what does the second finger of flemming’s left hand rule show ?

Answer 17

current (P-N)

Question 18

what does the thumb of flemming’s left hand rule show ?

Answer 18

force

Question 19

if current is parallel to the magnetic field what happens to the force ?

Answer 19

there is no force

Question 20

how can the motor effect be used in loudspeakers ?

Answer 20

• current flows in the coil
• this creates a magnetic field around the wire, which interacts with the permanent magnetic field - This creates a force (movement) on the wire
• an AC current is used, so the direction of the force is constantly changing - this makes the coil vibrate
• The vibrations cause sound (a longitudinal wave)

Question 21

how does electromagnetic induction create a voltage in a wire ?

Answer 21

• a wire (or coil) cuts through magnetic field lines (we can either move the coil, or create a moving magnetic field, but one must move relative to the other)
• this induces a voltage across the wire (if the wire is part of a circuit, this creates a flow of current)

Question 22

how is electromagnetic induction used in a power station ?

Answer 22

to generate electricity either by rotation of a magnet within a coil of wire or rotation of coil and wire with a magnetic field

Question 23

how can the voltage induced be increased ?

Answer 23

• moving the wire relative to the field faster
• using more coils
• using a stronger magnetic field

Question 24

how can the strength of a force be increased ?

Answer 24

• increasing the strength of the permanent magnetic field
• increasing the current
• in a motor adding more coils