electricity and circuits Flashcards by gabi moroni

describe the structure of the atom

proton = relative mass of 1 and relative charge of +1
neutron with relative mass of 1 and relative charge of 0
electron with relative mass of 0.0005 and relative charge of -1

How well did you know this?

Not at all

Perfectly

what do these circuit symbols look like
a. cell
b. battery
c. filament lamp
d. fuse
e. LED
f. power supply
g. resistor

a. —| |—
b. –| |—| |—
c. circle with a cross
d. box with a line throught the middle horzinotally
e. play button in a circle with a line throught it with lines pointing away from the top rigth and hand side
f. - +
—o o—- (dc)
—o (squiggle line) o— (ac)
g. a rectangle

How well did you know this?

Not at all

Perfectly

what do the circuit symbols for
a. variable resistor
b. ammeter
c. voltmeter
d. diode
e. LDR
f. thermistor
g. motor

a. rectangle with an arrow from bottom left to top right thoguht it
b. circle with A
c. cirlce with V
d. play buttonwith a line thoruhg it in a circle (the same as the LED but without the arrows)
e. a box in a circle with the lines going inside the circle but stopping at the edges of the box, arrows are going towards the circle from the top left
f. hockey stick thourhg rectangle where the only bit of the hockey stick through the rectangle is the line and the hitty bit of the hockey stick is in the bottom left below the box
g. circle with M

How well did you know this?

Not at all

Perfectly

describe the differences between series and parallel circuits

series circuit
- closed circuit
- the current is the same everywhere
parallel circuit
- branched circuit
- current splits into multiple paths

How well did you know this?

Not at all

Perfectly

how to work out parts of a parallel circuit

current splits into multiple parts
total current into a junction = total current in each of the branches
voltage is the same across each branch

How well did you know this?

Not at all

Perfectly

describe a voltameter

connected in parallel
with a component to measure the potential difference (voltage) in volt across it

How well did you know this?

Not at all

Perfectly

explain what potential difference is and what the volt is

pd is the energy transferred per unit charge passed
the volt is a joule per couloumb

How well did you know this?

Not at all

Perfectly

equation to work out energy transferred

energy transferred(J) = charge moved (C) * potential difference (V)

How well did you know this?

Not at all

Perfectly

what is an ammeter connected in series with

a component to measure the current in amp in the component

How well did you know this?

Not at all

Perfectly

explain what a current is

the rate of flow of charge
the current in metals is a flow of electrons

How well did you know this?

Not at all

Perfectly

equation to work out charge

charge (C) = current (A) * time (s)

How well did you know this?

Not at all

Perfectly

Describe that when a closed circuit includes a source of
potential difference there will be a current in the circuit

there will be current and pd because
pd = current * resistance

How well did you know this?

Not at all

Perfectly

where is current conserved at

a junction in a circuit

How well did you know this?

Not at all

Perfectly

Explain how changing the resistance in a circuit changes the
current and how this can be achieved using a variable resistor

greater resistance the harder it is for a charge to flow through component
-> so less current
a variable resistor changes the amount of resisance of the component changing the amount of current that flows in the circuit

How well did you know this?

Not at all

Perfectly

equation to work out potential difference

potential difference (V) = current (A) * resistance (ohms)

How well did you know this?

Not at all

Perfectly

Explain why, if two resistors are in series, the net resistance is
increased

(total resitance is the sum of the resistance in each component)
- resistance of two omponents is bigger than just one of them
-> because the charge has to push through both of them when flowing round the ciruit

How well did you know this?

Not at all

Perfectly

two resistors in series makes the net resistance increase, why does to resistors in parallel decrease the net resistance

total resistance is less than the branch with the smallest resitance in paralle
two resistors will have a smaller overall reistance than just one in parallel
-> as charge has more than one branch to take so only some charge will flow along each branch

How well did you know this?

Not at all

Perfectly

how to calculate currents, pd, resistances in SERIES ciruits

current is the same everywhere
pd is shared bewteen componenets
total resistance is sum of individual resitances of resistors

How well did you know this?

Not at all

Perfectly

explain the design and construction of series circuits for testing and measuring

components are connected end to end
all the current flows through all the components
so can only swith them all off at once

How well did you know this?

Not at all

Perfectly

Core Practical: Construct electrical circuits to:
a investigate the relationship between potential difference,
current and resistance for a resistor and a filament lamp - METHOD

connect circuit with component and ammeter in series
change variable resisotr resistance
measure current rhough pd across the component
take lots of readings from ammeter and voltmeter at differenet resitacnes
plot current against restance

How well did you know this?

Not at all

Perfectly

Core Practical: Construct electrical circuits to: investigate the relationship between potential difference,
current and resistance for a resistor and a filament lamp - USES

see how resistance hcnages as pd and current change

How well did you know this?

Not at all

Perfectly

Core Practical: Construct electrical circuits to: test series and parallel circuits using resistors and
filament lamps - METHOD

set up circuit
vary the output potential difference from the power supply
record readings from ammeter and voltmeter
replace the resistor with a filament lamp and repeat 2 and 3
connect second filament lamp to the circuit in parallel to the first
connect ammeters and a second voltmeter
vary output of pd of the supply again
write down current through ammeter and pd across each component

How well did you know this?

Not at all

Perfectly

Core Practical: Construct electrical circuits to: test series and parallel circuits using resistors and
filament lamps - WHAT YOU SHOULD FIND

series
- as pd increases the current through resitor increases
- similar non linear relationship between pd and current for filament bulb
parallel
- as pd increases so does current trhough each bulb
- total current rhough circuit si sum if the current trhough the two branches and this is larger than the total current through the series circuit with one filament bubl

How well did you know this?

Not at all

Perfectly

Explain how current varies with potential difference for FILAMENT LAMPS and how this relates to resistance

increasing current increases temperature of filament lamp
so resistance increases
non linear (curved graph) - resistance varies

Explain how current varies with potential difference for diodes and how this relates to resistance

- current flows through a diode in one direction - diode has a high resistance in the opposite direction - non linear (curved graph)

Explain how current varies with potential difference for the fixed resistors and how this relates to resistance

- current is directly proportional to pd (if temperature stays the same) - different resistors have different resistnaces -> so their graphs have different slopes

Describe how the resistance of a light-dependent resistor (LDR) varies with light intensity

- if bright the resistance falls - if dark the resistance is high

Describe how the resistance of a thermistor varies with change of temperature

- if hot the resistance drops - if cool the resistance goes up

Explain how the design and use of circuits can be used to explore the variation of resistance in filament lamps

- connected to DC of 2, 4 ,6 -12 V - connect filament lamp to ammeter in series and voltmeter in parallel - measure current for each voltage

Explain how the design and use of circuits can be used to explore the variation of resistance in diodes

- connected to DC of 1, 1.5 , 2, 4, 6, ...12V - connect to ammeter in series and voltmeter in parallel - measure current for each voltage - switch diode other wat round to record current for -1, -1.5 etc

Explain how the design and use of circuits can be used to explore the variation of resistance in thermistors

- constant voltage of 12 V - connect to ammeter - place in ice water with thermometer - measure current at 0 degrees - add hot water ans stir measuring current at 10, 20 ... 60 degrees - calcultae resistance

Explain how the design and use of circuits can be used to explore the variation of resistance in LDRs

- constant voltage of 12V - connect to ammeter - shine lamp onto LDR and measure current - move lamp 10cm away and measure current - keep doin ghtis until 50 cm - caluclate resistance at each light intensity

whta happens when there is an electric current in a resistor

there is an energy transfer which heats the resistor

Explain that electrical energy is dissipated as thermal energy in the surroundings when an electrical current does work against electrical resistance

- current increase electrons have more enery - electrons collise with ions in resistor - current is doing work against resistor here - so transfers energy to the ions so they virbate mroe (heating) -> more difficult for electrons to flow through the resistor

why is there an electric current in a resistor when there is an energy transfer which heats the resistor

- electrons collide with ions in the lattice - current is doing work against resistance - which transfers energy to ions - so they vibrate more heating the resistor

Explain ways of reducing unwanted energy transfer through low resistance wires

- low resistance wires means less energy loss - as current flows through the circuit - this make it more efficient

Describe the advantages the heating effect of an electric current

- useful if you want to cook something (ex toasters) - high temeprature of current in the coil gives of IR radiation -> which transfers energy and cooks

Describe the disadvantages of the heating effect of an electric current

- if temperature gets to high then components in the circuit could melt and stop working

describe the advantages of the heating effect of an electric current

- heats things like food -> when current is passed through coil its temperature increases -> IF radiation transfers energy

equation to work out energy transferred

energy transferred (J) = current (A) * potential difference (V) * time (s)

describe power

- energy transferred per second - measures in Watts

equation to work out power

power (W) = energy transferred (J) / time taken (s)

Explain how the power transfer in any circuit device is related to the potential difference across it and the current in it

- because the pd is how much energy each unit of charge transfers and the current is how much charge passes per time

equation to work out electrical power using potential difference

electrical power (W) = current (A) * potential difference (V)

equation to work out electrical power using resistance

electrical power (W) = current squared (A) * resistance (ohms)

Describe how, in different domestic devices, energy is transferred from batteries

from batteries - chemical energy -> electrical energy -> mechanical energy (motor) or themral energy (heating)

Describe how, in different domestic devices, a.c. mains to the energy of motors and heating devices

from A.C mains - electrical energy -> mechanical energy (motor) or thermal energy (heating)

explain the difference between direct and alternating voltage

- direct voltage = (DC) is the movement of charge in ONE DIRECTION - alternating voltage (AC) the charges are constantly CHANGING direction

recall what direct current (dc) is and what supplies it

- movement of charge in ONE direction only - cells and batteries supply direct current

recall what alternating current (ac - mains) is

- movement of charge changes direction

recall the frequency and voltage in the UK domestic supplies a.c

- frequency = 50 hz - voltage = 230 V

explain the difference in function between the live and neutral mains input wires

- live wire carries voltage - neutral wire completes the circuit so current flows through live and neutral wires

explain the function of an earth wire in ensuring safety

- the safety wire used to stop appliance becoming live -> carries current away if something goes wrong

explain the function of fuses in ensuring safety

- if a large current passes through live wire the fuses heat up and melts -> breaking the circuit preventing a fire or damage

explain the function of circuit breakers in ensuring safety

breaks circuit preventing a fire or damage - turn off quicker than a fuse melts - they can be reset which is easier than replacing a fuse - more expensive

explain why switches and fuses should be connected in the live wire of a domestic circuit

- because the current passes through the live wire making the fuse heat up and melt - which breaks circuit and prevents a fire or damage

recall the potential differences between the live, neutral and earth mains wires

- neutral - 0V - live - 230 V - earth - 0V

Explain the dangers of providing any connection between the live wire and earth

- can create a low resistance path to the earth - huge current - fire

Describe, with examples, the relationship between the power ratings for domestic electrical appliances and the changes in stored energy when they are in use

- power rating is the power of the appliance when in use - greater power ratings = more energy consumption - so uses more energy in a given time

electricity and circuits Flashcards

topic 10