closest distance eye can focus on approximately 25cm
7 of 30
As eye focuses on closer objects
power decreases, lens changes shape, and focal length decreases
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Finding centre of mass (4)
1) Suspend shape and plumb line from same point. 2) Draw line along plum line 3) Suspend from different pivot and do same. 4) Centre of mass is where they cross.
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Centre of mass
Point at which whole mass is concentrated
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Liquids are virtually
incompressible
11 of 30
Since they can flow
a force applied at one point can be transmitted to other points.
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Pressure in liquid is
transmitted equally in all directions
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Magnetic field around current carrying wire
corkscrew rule
14 of 30
coil of wire aka
solenoid
15 of 30
electromagnets can be
turned on/off
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increase strength of magnetic field around solenoid by
adding soft iron core through middle of coil
17 of 30
magnetically soft
magnetises/demagnetises very easily
18 of 30
electromagnets can be used for
picking things up, some cranes, and dropping stuff down
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motor effect
lemmings RH rule
20 of 30
2 factors speed up motor effect
more current stronger magnet
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split ring commutator
swapping polarity of DC to keep motor rotating in same direction by swapping contacts every half turn
22 of 30
Define electromagnetic induction
Creation of P.D across conductor which experiencing change in magnetic field
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step up transformers
step voltage up : more turns on secondary than primary coil
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step down transformers
step voltage down : more turns on primary coil than secondary
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Stages of transofmrers
...
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1
primary coil produces magnetic field
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2
a.c produces changing magnetic field
28 of 30
3
induces p.d across secondary coil, inducing ac in circuit attached to secondary coil
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switch mode transformers:
operate higher frequencies than traditional transformers and operate at 50-250kHz used as mobile/laptop chargers
30 of 30
Other cards in this set
Card 2
Front
With magnifying glass object being magnified must be
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