Electricity and electrostatics Flashcards

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1
Q

what do conductors do

A

they allow charged particles to move through it. The delocalised sea of electrons in a metal wire are free to move

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2
Q

what do cells/batteries do

A

more electrons will move towards the positive terminal. there is a net flow of current through the wire

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3
Q

which way do electrons flow

A

they flow from positive to negative terminal(syllabus of iGCSE) but actually they flow from the negative terminal to the positive terminal because electrons are negatively charged

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4
Q

definition of charge

A

Charge is a property of a body which experiences a force in an electric field

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5
Q

definition of current

A

rate of flow of charge

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6
Q

what is the equation linking charge, current and time

A

Q = I x T (charge (coulombs[c]) = current(amperes[A]) x time(seconds[s]))

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7
Q

what does a cell do

A

gives energy to the elctrons

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8
Q

what does a wire do

A

carries current

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9
Q

what do bulbs do

A

converts electrical energy to light

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10
Q

what do ammeters do

A

measures the current

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11
Q

what do resistors do

A

opposes flow of electrons

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12
Q

how does current work in series

A

current stays the same everywhere in series

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13
Q

how does the current in parallel circuits work

A

the current will go into paths proportional to the resistance following the rule V = IR

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14
Q

what is voltage

A

energy/charge

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15
Q

how does voltage work in series circuit

A

the total voltage will be split proportionally to the resistance of the components following the rule V = IR (if the resistance increases, the voltage will also increase

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16
Q

how does voltage work in parallel

A

the voltage will be the same everywhere, unless there are multiple components in a single path

17
Q

how many joules of energy is given to each coulomb of charge that passes through the cell if the cell is 1.5V?

A

1.5J of energy

18
Q

formula linking voltage, energy and charge

A

V = E(J)/Q(C)

19
Q

how can you measure voltage

A

measure voltage using a voltmeter which is connected in parallel with the component we are interested in

20
Q

rules for resistance in series

A

R1 + R2 = RT(total)

21
Q

rules for resistance in parallel

A

1/R1 + 1R2 = 1/RT

22
Q

why does resistant increase in an filament Light bulb

A

-The current increases, which leads to the the electrons transferring more KE to the metal ions
-The ions vibrate more, increasing the chance of electrons scattering, so the resistance increases

23
Q

what name is given to a light bulb that doesnt increase resistance as the current increases

A

ohmic

24
Q

what is a diode

A

a semi-conductcor device that only allow current to flow one way

25
Q

what is a thermistor

A

The resistance of a thermistor depends on its temperature. At low temperatures, the thermistor has a high resistance. As the temperature increases, the resistance decreases.

26
Q

uses of a thermistor

A

A thermistor can be used in thermostats or heat activated fire alarms.

27
Q

what is an LDR

A

The resistance of a LDR depends on light intensity. At low light levels, the LDR has a high resistance. As the light intensity increases, the resistance decreases.

28
Q

uses of an LDR

A

A LDR can be used as a sensor in cameras or automatic lights that come on when it gets dark.

29
Q

what are diodes used for

A

converting alternating current into direct current

30
Q

why does the resistance increase of a filament lamp as the voltage increases?

A

-lamp heats up due to higher voltage
-ions vibrate more
-greater chance of electron collisions
-resistance increases

31
Q

memorise symbols

A

-google it

32
Q

why should domestic lighting be in a parallel circuit

A

-allows lights to work independently
-they all get the same mains voltage (230V)
-so different areas can get different light intensities

33
Q

electrical conductors

A

conducts charge easily

34
Q

electrical insulators

A

do not conduct charge very well so current cannot flow

35
Q

what is a static charge

A

charge which builds up in one space and is not free to move

36
Q

what causes sparks

A

-when an electrical charge builds up on an isolated object, the voltage between the object and the earth increases
-if the voltage gets large enough, electrons can jump across the gap between the charged object and earth/earthed object, causing a spark

37
Q

how is static electricity helpful in an inkjet printer

A

-droplets of ink are forced out of a fine nozzle, and are then given an electrical charge
-droplets are deflected as they pass between two metal plates. A voltage is given to the plates, one is -ve, one is +ve
-droplets are attracted to the plate of the opposite charge and are repelled from the plate with the same charge
-size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper

38
Q

how is static electricity helpful for photocopiers

A

-image plate is +vely charged. An image of what you are copying is projected onto it.
-whiter bits of what you are copying make light fall on the plate and the charge leaks away there
-charged bits attract negatively charged black powder, which is then transferred onto positively charged paper
-paper is heated so the powder sticks