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physics > electricity > Flashcards

electricity Flashcards

1
Q

which particle in an atom can freely move around

A

delocalised electrons

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2
Q

what is static electricity

A

buildup of charge in 1 location caused by 2 insulators

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3
Q

like charges __ unlike charges ___

A

repel,attract

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4
Q

when are electrons transfered

A

when objects become charged

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5
Q

what happens when 2 insulators are charged by friction

A

one ends up negatively charged due to having elections being lost and the other becomes negatively charged because excess electrons were transfered

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6
Q

what happens when a negatively charged insulator touches another insulators

A

the negatively charged insulator attracts the protons in the normal insulator when the charged insulator discharges its electrons to the normal insulator

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7
Q

how does lightning happen

A

in storms 2 clouds rub against eachother which causes friction between the water vapours,then one of the clouds becomes charged and is attracted to the positive ground which causes it to discharge

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8
Q

whats the unit and definition for current

A
  • rate of flow charge
    measured in amperes (A)
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9
Q

what does I=Q/T mean

A

current in A is equal to charge in columbs divided by time in seconds

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10
Q

whats the unit and definition for voltage

A

-energy transfered per columb of charge (basically the force applied to move electrons)
-volts

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11
Q

whats the unit and definition for resistance

A

-anything that opposes the electric current
-ohms (Ω)

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12
Q

whats the difference between cells and batteries

A

a cell is a single unit which converts chemical to electical energy
battery is a collection of cells

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13
Q

whats the symbol of a fuse what is its function

A

its like a resistor with a line drawn through the middle , its designed to melt and break when the current exceeds its limit

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14
Q

what is meant by LED and LDR

A

-LED (play button and arrows go outwards in symbol) is light emitting diode, it emits light while allowing current to flow in only 1 direction
-LDR (resistor with arrows pointing inwards) is light dependent resistor

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15
Q

which way are ammeters connected and what do the measure

A

connect in series and measure current

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16
Q

which way are voltmeters connected and what do the measure

A

connect in parallel and measure voltage

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17
Q

whats the relationship between voltage,energy transfered and charge

A

V=E/Q

18
Q

what happens in parallel circuits

A

current is divided and the voltage stays the same

19
Q

what happens in series circuits

A

voltage is divided and current stays the same

20
Q

whats happens when resistance increases

A

voltage and current will also increase to overcome it

21
Q

what is ohms law

A

current is proportional to voltage at constant temperature and resistance

22
Q

what happens if temperature increases

A

resistance increases due to particles vibrating more frequently with more kinetic energy

23
Q

what are the iv characteristics of a fixed resistor

A

-ohomic conductor
-straight line and linear graph

24
Q

if y=current and x=voltage then

A

the steepest line is the highest resistance

25
Q

if y=voltage and x=current then

A

the shallowest line is the highest resistance

26
Q

how do fillament lamps work

A

the wires heat up then electric energy is transferred to infrared rays that emit light

27
Q

whatre the iv characteristics of a filament lamp

A

-nonohomic conductor
-as current increases theres more of an heating effect so the wire heats up more causing increases resistance due to electrons coliding more often
-line plateus due to max voltage

28
Q

what are the iv characteristics of a diode

A

at negative end theres super high resistance and at the start of positive end the voltage and current are trying to overcome resistance then finally the resistance decreases

29
Q

what are the different variables for the required practical

A

controlled; resistor (filament lamp/diode/fixed resistor)
dependant(measured): current
independent(changes): voltage

30
Q

whats the procedure for the required Practical

A
  • connect any resistor filament lamp or diode to a series circuit that looks like this (draw diagram with variable power supply,ammeter,volmeter connected with lamp in parallel)
    -keep resistance constant and change voltage using variable power supply
    -flip batteries to measure both polarities
    -plot iv graph and calculate resistance
    -(for each component explain the characteristics theyll get when they plot it)
31
Q

when does resistance increase in a thermistor

A

when its cold due to it being a negative temp coefficient so it acts opposite to normal resistor .

32
Q

in thermistor, as temp increases, resistance ___

A

decreases

33
Q

in LDRs as light increases,resistance __

A

decreases

34
Q

what happens in ldr when its dark

A

very high resistance so more current is neederd to overcome it

35
Q

how do LDR sensors work when its dark

A

the resistance is very high so more voltage and current is needed to overcome it. since lamp is connected in parallel to ldr the voltage is shared so the voltage increases in both ldr and lamp and more light is emitted

36
Q

what happens to LDR sensors when its light

A

the resistance decreases so less voltage is needed to overcome it. since in lamp is connected in parallel to ldr voltage is shared, not much voltage is transfered through both the lamp and ldr so little light is emitted

37
Q

why will a decrease in light intensity of LDR decrease ammeter readings

A

because resistance will increase as theyre inversely proportional

38
Q

can static electricity happen between a insulator and conductor?

A

no because they wont transfer energy to eachother

39
Q

why will resistance of metal filament increase as voltage increases

A

since the filament is metal it contains free electrons so when current flows through so does voltage and the temp increases which causes atoms to virbrate faster and colide more frequently

40
Q

voltage= current X _____

A

resistance

41
Q

describe how a student would use __ circuit to determine resistance in resistor r

A

switch on the battery and close the switch then record initial values of both ammeter and voltmeter. adjust the variable resistor to change the current then take the new reading. plot an iv graph and find the gradient R=V/I

42
Q

what is the unit of power

A

watts (W)

physics (10 decks)

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