Topic 4 Electricity Flashcards
Draw a cell
Lamp
open switch
closed switch ammeter
check sheet .
What happens when you clsoe the setich in a series circuit ?
- Electrons flow out of the cells and move around ciecuit .
- Current flows from the NEGATIVE end of the cell to the POSITIV end of the cell ..
- electrons carry energy from the cell and pass this neergy to the components of the circuit
example , what happens to the lamp ?
Electrical energy is transferred to light and thermal energy .
-when electrosn return to POSTIVE end o f thr cell , they carry less energy than they did at the negaitve end .
Coventional current < crrent flows from neagtive top ositve end .
What is a series circuit ?
- There anre no branches , current will only flow in one pth .
- An ee;ectric current is a flow of electric charg aroudn a circuit . Unit of electric current is Amps ‘A’
- Measure current ina circuit usign an ammeter .
Key fact about current in a series circuit ?
-Current is never used up in a circuit , ina series current , current is the saml all he way roudn (ammter same reading evryhwere ).
conventional current
flow from positive end to negaitie end > althgouh that isnt true thats how scientsits draw.
What are parallel circuits ?
Contain branches
current spllits some of the current passses thorugh bulb
Crrent n branches ADDS UP TO TOTAL current leaving the cell .
energy stroe store changes
Cells storees chemical enegry trandsferred to electrons electricl chage and passing thoruhg the componenes transferred as other forms of energy .
What is Potential difference ?
Also known as voltage
-tells us how much energy is transferred in electrical circuilt
1V = 1 joule of energy transfered to ech coluloumb of charge moving through the cirictui .
Measure Potential difference usign voltemre .
More compoenents in a serie circuit
lamps and stuff will be dimemr as total neergy has to be shared between them .
But the total pd of components is euqal to the total potential difference acros the cell .
Which one is bright
one lamp with 6v
or one with 3v
Lamp with volatgeo f 6v is brighter as it is transferrign more neergy than lamp with 3v .
for components connected i parallel …
potentnial difference across each component is the sam e.
What is a battery ?
A batetyr is wo or more cells connected togther .
-cells in batetry must be correct directin
left isde positive .
What is electric charge measured in
Coloumbs A current of 1amps is = 1 coloumb size of electric current is th same as the rate of flow of electric charge we work out charge charge =current (a)*time(s) c*as
Why does energy transer tke lace ?
- electric current is a flow of electrons thorugh a conductor like a metal wire .
- As more elcecorns collide witha toms of metlas . eLECTICAL ANERGY TRANSFFERED INTO THER FORMS OF ENERGY LIKE THERMAL .
What is resitacne ?
Resistance is the volatge requuired to drive a currrnet thorugh a component .
Higher potential difference (reading on volt meter voltge = higher resistancce a larger amounto f energy needed to drive current thorhg a component .
What is resistanc emeasured in
Ohms
Pie kinda symobol
resitaicne is equal to potential difference (v) voltage/ Current(a)
V/R*i
POTENTIAL DIF RQP First STAGE
- resistor is set in series with an ammeter and a variable reissotr and a battery
- Volt meter in parallel to ressitor .
POTENTIAL DIF RQP Second STAGE
- Use volt meter to measure voltage across the reissitor .
- use an ammetert to red current thorugh resitor .
- Read values and make a tablE . Adjust variable resitor and record reading on volt and ammeter . Do seeral time to get a range of reaidngs.
POTENTIAL DIF RQP third STAGE
-Swich direction of battery so volatge reevrsed . Voolmeter and ammeter will have negtive values continuign doing several times make tbale .
POTENTIAL DIF RQP sevetj STAGE
-Graph should look striaght line passing though sexxto .
Current moving thoruugh a resitor is direclty propeorional to potenital difference . resistor is an Ohmic conductor resistance remains the same on changing the current and voltage.
-IFF WE CHANGE VOLTAGE still get sraight line . Only see a striaght line tho if the resisotr temperature is kept constant so make sure dont keep on circuit for too long .
What happens if we do the rqo wih a filament light bulb ?
Current is not proportional to potn=ential differnc e.
-As this current increase s, tempearutre of filmanet lamp increases . Casuing resistance increases . so curvey line .
What happens if we do the rqp usign a diode ?
Diode needs an extra resisotr in a circuit to keep current low and portect diodie s didoie is esily damaged by hgih current .
As current low ned a sensite ammeter , milliameter .
-Only get volatge 0.6-0.7v . voltage incresing beyond this point , current rises hsaeply .
Why is there no current if the votlage reversed in a diode ?
-As revsere direction , diode as a high resistance .
Resistor rqp equipment
-batteyr
ammeter - current of circuit
voltmeter - for voltage across wire
resistior rqp first stage
Attach a wire to metre ruler using tap e.
- Attch this to a circuit using crocodile clips .
- Only part of circuit between two corocdiel clips is attached to circuit .
- Move crocodile clips apart to increas length of circuit .
Resistor Rqp graph ?
-Resistanc eid directily proprotional to length of wire .
One problem with resistor rwp >?
- Small resitance whn length of wire xero , resistance called xeror error it should be zero on grpah but it isnt .
- SO subtract zero error from all our readigs .
- zero error made bye qupiment as it diffuicult to clip corcodile clip at exactl zero ,a slo resistance between clip and wire .
Second problem with resitor rqp ?
Tempeature - if the temperaure of wire increases , the resiance will aslo icnreas e.
- Reduce this by lwoerign potential differnec e, current low , reducing heating . Milliammeter
- Or only turn on the currnet when taking a reading .
What does a varibale resistor do ?
-It changed the resitance in a cirucit by chaning the length in a ire ,. Box with arrow varibale resisotr .
