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Physics > Magnetic Fields > Flashcards

Magnetic Fields Flashcards

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1
Q

what is the relation between like and unlike magnetic poles?

A
  • N and N repulsion

- S and N attract- uniform field

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2
Q

when drawing magnet poles which was do the arrows go?

A

north to south

-closer lines together stronger the magnetic field

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3
Q

what is a permanent magnet?

A
  • i.e bar magnets

- produce own magnetic field all the time

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4
Q

what is a induced (temporary) magnet?

A

only produce magnetic field while they’re in another magnetic field

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5
Q

what are the 3 main magnetic elements?

A

iron, nickel, cobalt

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6
Q

what alloy of the main magnetic elements are magnetic?

A

steel- alloy of iron

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7
Q

how does a compass relate to evidence that the core of the earth must be magnetic?

A
  • always points to north pole

- because earth generates own magnetic field

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8
Q

what are permanent magnets?

A
  • eg bar magnets

- produce their own magnetic fields all the time

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9
Q

what are induced magnets?

A

-only produce magnetic field when in another magnetic field

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10
Q

what does a moving charge through a long straight conductor (wire) create?

A

magnetic field

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11
Q

how do you work out how large the current is around a wire?

A
  • closer to wire stronger the current

- closer circles are stronger the current

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12
Q

what does the right hand thumb rule show you?

A

the direction of the magnetic field

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13
Q

how do you do the right hand tub rule?

A

thumb points in the way of the current so the fingers follow in the way of the magnetic field

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14
Q

what does the strength of the field depend on?

A
  • size of current

- distance form conductor

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15
Q

what is solenoid?

A

long coil of wire

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16
Q

what is a solenoid an example of?

A

an electromagnet

17
Q

what do the individual fields in a solenoid do?

A
  • add to form a strong uniform field along centre

- cancel to give weak field outside the solenoid

18
Q

what happens when a current carrying a conductor is placed near a magnet?

A

magnet experiences a force and an equal opposite force acts on the magnet

19
Q

what are magnetic forces due to ?

A

magnetic forces are due to interactions between magnetic fields

20
Q

what is Flemmings left hand rule used to show?

A

represent directions of force, current, and magnetic field

21
Q

how does Flemmings left Hand rule work?

A
  • put first and second finger in an L shape and thumb up
  • tumb= motion, force
  • first finger= magnetic field
  • second finger= current
  • fit to a diagram and direct will be given
22
Q

what is the equation to work out the size of a force?

A 
F= B x I x L
force(N)= magnetic density/flux (T) X current(A) X length (m)
23
Q

what are the factors with effects the size and direction of created potential difference?

A
  • increase strength of magnetic field
  • more coils
  • increase speed
24
Q

how does the magnetic field produced oppose the original change?

A
  • current produces own magnetic field

- magnetic field toys to act against the charge

25
Q

what does induce mean?

A

create

26
Q

what can a transformer do?

A

change the size of a alternating voltage

27
Q

what is the national grid?

A

network of wires and transformers that connect Uk power stations to consumers (anyone who uses electricity)

28
Q

why is energy transferred at different voltages at the national grid?

A
  • high voltage from power stations
  • lower voltage for domestic use
  • improves efficiency by reducing heat loss in transmission lines
29
Q

why are step up transformers used in the national grid?

A

boost p.d. high(400,000V) and keep current low

30
Q

why are step down transformers used in the nation grid?

A

-bring down to safe and usable levels for consumer

31
Q

what is the equation for transformers which are 100% efficient?

A 
Vp X Ip = Vs X Is
V= voltage (V)
I= current (A)
p= primary coil
s= secondary coil

Physics (11 decks)

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