paper 3 magnetism

Question 1

What is accuracy vs precision?

Answer 1

• accuracy is how close something is to the true value
• precision is how similar your results are, to each other

Question 2

What is repeatable vs reproducible?

Answer 2

• repeatabiilty is when you repeat an experiment using the same method and equipment, to get similar results
• reproducibility is when someone else repeats your investigation, or if you you do the same investigation with different equipment, and the results are similar

Question 3

what are levers?

Answer 3

• Levers transmit the turning effects of a force
• they are force multipliers, where the output force> input force, same moment, where the output force distance is is less, and moment is same

Question 4

what are gears?

Answer 4

• transmits turning effects
• the work done is the same
• moment multiplier, as same force, but larger distance from cetnre of wheel (radius)
• wheels move in opposite directions

Question 5

what is upthrust? What causes floating?

Answer 5

• uprthrust: caused by the pressure of the particles at the bottom, greater than pressure at top
• floating is when upthrust is greater than weight

Question 6

what is an alternating current and an alternator?

Answer 6

• current direction constantly changes, alternation p.d.
• mains supply in UK, 50Hz and 240V
• alternator produced a.c.. coil of wire spins between poles of the magnets, cutting magnetic field lines, so the wire has induced p.d., current, mag

Question 7

what is a direct current and a dynamo?

Answer 7

• d.c., current and p.d. stays the same
• dynamo, same structure of the motor, generating current

Question 8

what is the concept behind generators?

Answer 8

• movement produces p.d. in the wire, a current produced if a circuit

Question 9

How do loudspeakers and microphones work?

Answer 9

• microphone: sound waves, diaphragm moves in and out, p.d. induced, electrical signal
• loudspeaker: changing p.d. changing current, force on coil of wire in mag field, spins, sound wave

Question 10

How do transformers work?

Answer 10

• a.c. in primary coil, induced a.c. in secondary coil
• more secondary coils: greater output p.d.
• a.c. induces alternating mag field in the iron core, which induces alternating p.d. in secondary coil, which becomes a.c. if connected to circuit

Question 11

What is EM induction?

Answer 11

• producing induced p.d. if wire in changing magnetic field, cutting field lines, producing magnetic field