P2 Electricity Flashcards
Explain what a thermistor is.
A type of resistor tha resistance changes depending on the temperature.
Resistance decreases as temperatureincreases.
What is Power ?
& equasions used to calculate it.
How quickly energy can be transfered.
E=Pt / P=IV / E=QV
What is and Electric current?
(+ units)
The flow of electric charge.
Measured using an ammeter, Amps(A)
High current = lots of electrons moving fast
Low current = few electrons slow moving
What are electric circuts?
They transfer energy, energy is carried around the circut by electrons.
Circuts have different componants to alow them to complete energy transfer.
What is Potential Difference?
(+ units)
The amount of energy carried by each electron.
Measured using a voltmeter in volts (V).
energy per unit charge
What are rules for paralel circuts?
1) current in each branch of the circut has to add up to total current
2) Potential difference of componant in a branch is the same as battery.
What are the rules for series circuts?
1) cells in series add up
2) current is the same everywhere
3) p.d. across componants adds up to p.d. across the battery
What is an IV characteristic graph?
A grap that plots current(y-axis) against p.d. (x-axis)
all componants can have an IV characteristic graph.
If current and P.d. are directly preportional on the graph it is an ohmic conductor.
Explain what an LDR is.
A light dependant resistor is a resistor that depends on light intensity. In bright light the resistance falls.
Componant in circut
What causes resistance?
As electrons flow through the wire they collide with metal ions in the wire. This slows them down causeing resistance.
What is an Ohmic conductor?
Obeys ohms law but temperature cant change.
What is Resistance like in a series and Paralel circut?
Series - adds up
Paralel- resistance is allways less than bc current has multiple paths can flow.
What is the Equasion for resistance, current and P.d?
P.d. = current xresistance
V=IR
volts(v) Amps(A) Ohms(Ω)
What is ohms law?
says - “p.d. is directly perportional to current provided the temperatre is constant “
Complete the table
|series |paralel
current| | |
p.d. | | |
resistance | |
current| same|split|
p.d.| split | same|
resistance| adds up |less than|
What factors effect resistance of a metal wire?
Temperature- temp ↑ resistance ↑bc likely hood of metal ions colliding ↑
Length - longer wire= more metal ions = more collisions = more resistance
Area - ↑ area ↓resistance more routes for charge
Material Type - more/ less resistive
Explain what a diode is.
Diodes only alow current to flow in one direction. Resistance depends on the direction of the current, high resistance depends on the direction of the current.
What happens if there is a break in the to types of circut?
In SERIES circut (if breaks) the current wont flow bc the circut isnt one complete loop/
In PARALEL circuts switches can turn branches on and off and depending on which branch breaks the circut could still work.
Describe these quantities and give units.
Energy
Charge
Power
(in terms of electricity)
Energy : gets transfered around the circut (J)
Charge : positive, negative, neutral (C) Coulombs
Power : how quickly energy is transfered (W)watts
What is the resolution?
Resolution of a device is the smallest change a device can detect.
Explain circut symbol for a variable resistor
Explain what a variable resistor is.
(rectange/ resistor with an arrow pointing north east or top right)
The slider on a variable resistor is used to change the length of the coil so current can be increased or decreased, varied.
eg. dimmer light, volume control.
What equasion links time, charge and current?
Charge = current x time
(Q)coulombs (A)amps (s)seconds
Q=It I =Q/t t=Q/I
What is resistance?
(+ units) (+ high / low resistance = ….)
How hard it is for charge to flow through a componant. Measured by calculation in ohms(Ω).
High resistance - hard for electrons to flow - small current
Low Resistance - easy for electrons to flow - large current
What equasion links Energy, Charge and P.d?
Energy = P.d. x Charge
(J) joules (V) volts (C) coulombs
E = QV Q =E/V V=E/Q
