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BMAT > Physics 4 -Electricity > Flashcards

Physics 4 -Electricity Flashcards

1
Q

Charge is carried by what in solids

A

electrons (negatively charged)

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2
Q

Charge is carried by what in liquids

A

Charged Ions

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3
Q

Delocalized electrons are found where?

Why are they good conductors

A

Metals

Allows electrons to move around

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4
Q

In thermal conductors, what is passed from one particle to particle

A

kinetic energy

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5
Q

With a polythene rod, which way does electrons move to with the duster

What happens to the charge of the duster?

A

Duster –> Polythene rod

Duster becomes positive charged

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6
Q

With the acetate rod, which way does electrons move?

What happens to the charge of the duster?

A

Acetate –> Duster

Duster becomes negatively charged

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7
Q

Opposite charges…?

A

attract

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8
Q

static electricity is created when

A

Two insulating materials are rubbed together

Of the insulators gets a load of electrons dumped on it
Like charges try and repel and cant as they are stuck

Creating static charge

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9
Q

What creates a spark with static charge

A

Electrons realigning themselves

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10
Q

what type of clothing is notorious for building up static charge when rubbed against eachother

A

Synthetic clothing

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11
Q

What can solve static electricity problems

A

Earthing

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12
Q

What is used to earth

What does this allow

A

Conductor (copper wire)

easy route for static charge to go to the ground

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13
Q

Current is what

What units

A

flow of electric charge around the circuit

Amperes (amps)

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14
Q

Voltage is what

A

Is whats needed to cause current to flow through a component

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15
Q

the greater the resistance across a component, the smaller the ……..

A

current that flows through

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16
Q

Current =

A

Time

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17
Q

Charge is measured in

A

Coulombs

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18
Q

Potential Difference is the ….

A

Work done per unit charge

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19
Q

PD (V) =

A 
  Charge (Q)
20
Q

What does a voltmeter measure

A

Potential Difference between two points

21
Q

On the circuit diagram, which way does the current flow from (on the battery)

A

Comes out of the thin lined one

22
Q

Current through a resistor is directly proportional to what

A

P.D. (voltage)

23
Q

In a filament lamp, as temperature increases, what happens to resnstance

A

Increases

24
Q

resistance from heat increases with temperature why

A

Ions in conductor vibrate more

Meaning electrons cant move through easily

And current cant flow easily

25
Q

V =

A

I x R

26
Q

Energy transferred(power) =

A

Power x Time

27
Q

Power=

A

Current x Potential Difference

28
Q

Energy transferred (charge) =

A

Charge x Potential Difference

29
Q

electromagnetic Induction

A

Creation of a potential difference across a conductor which is experiencing a change in magnetic field

30
Q

What 4 factors affect the size of the induced voltage from an elecromagnetic induction

A

Strength of magnetic field

Cross sectional area of the coil

Number of turns on coil

Speed of movement

31
Q

If your turning the magnet faster, what two things will happen?

A

Higher peak voltage

Higher frequency

32
Q

using flemings right hand rule, what does each finger show

A

thumb - Motion (direction of coil)

1st finger - Field (north-south)

2nd finger - current (points towards -)

33
Q

Transformers only work on what

A

A.C current

34
Q

Step up transformers have a higher P.D across which coil?

A

secondary coil

35
Q

Step down transformers have a higher P.D across which coil?

A

Primary coil

36
Q

Transformer equation with current

A

V(p) I(p) = V(s) I(s)

37
Q

Transformer equation with turns

A

V(p)/V(s) = N(p) / (Ns)

38
Q

Switch Mode Transformers operate between?

A

50KHz - 200KHz

39
Q

Switch mode operate at a higher?

A

frequency to traditional transformers

40
Q

Mains supply frequency is ?

A

50Hz

41
Q

What do Isolating transformers do?

A

the dont connect to the mains hence are safer

42
Q

how many turns are on the primary/secondary coils in an isolating system?

A

Equal number

43
Q

Is the voltage changed in an isolating transformer?

A

no

44
Q

Power loss =

A

Current^2 x Resistance

45
Q

If the current is 10x bigger, what happens to power loss?

A

100x larger

BMAT (21 decks)

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