P4 Electric circuits (paper 1) Flashcards
What makes up electricity
electrons
define current
the rate of flow of charge
What is the unit for current
Amps (A)
What is voltage
the amount of energy per charge
What is the unit for voltage
Volts (V)
What does resistance do
slow the current down, resisting the flow of charge
What is resistance measured in
Ohms (Ω)
Define ohms law in a sentence
Voltage and current are directly proportional (r=v/i)
When does more charge pass around a circuit
when a larger current flows
ammeter
bulb
buzzar
cell
diode
LDR
LED
motor
resistor
switch
thermistor
variable resistor
voltmeter
battery
What makes something and ohmic conductor
its current flowing through is directly proportional to the potential difference (voltage) across it
Give an example of an ohmic conductor
a wire
a resistor
describe what a graph of a wire would be like
the voltage and current are directly proportional
Why does resistance change in a filament bulb
because of the heating effect
What happens in the heating affect
- collisions between electrons and metal ions
- friction caused
- causes heat which
- increases resistance
what does the resistance of a diode depend on
the direction of the current
Why does the resistance of a diode depend on the direction of the current
because they will let current flow one direction but have a very high resistance in the other direction
What does the term ‘I-V characteristics’ refer to
a graph which shows the current flowing through a component changes as the potential difference is increased
what I-V characteristics do linear components have
straight line
what I-V characteristics do non-linear components have
a curved line
describe the relationship of an I-V graph of a filament bulb
It starts directly proportional, overtime the gradient slowly decreases - the resistance increases
Why does the resistance start to increase in an I-V graph of a filament bulb
because of the heating effect
in an I-V graph how does resistance and gradient relate
as gradient goes down (flatter) resistance goes up
What is LDR short for
Light dependent resistor
what is an LDR
a resistor that is dependent on the intensity of light
How does light affect the resistance in an LDR
as light intensity increases resistance decreases (lurd)
What does resistance in a thermistor depend on
temperature
How does temperature affect the resistance in a thermistor
As temperature increases resistance decreases (turd)
What type of graph is this
a diode I-V graph
What type of graph is this
a filament bulb I-V graph
What type of graph is this
A wire I-V graph
What type of graph is this
An LDR graph
What type of graph is this
a thermistor graph
what can you use LDRs and thermistors in
sensing circuits
What are sensing circuits
circuits that can be used to turn on or increase the power to components depending on the conditions they are in
What path does electricity take
the one with the least resistance
Describe the appearance of series circuits
They are one loop and all of the components are connected in a line, end to end
What is potential difference (voltage) like in series circuits
it is shared between various components
the pd of all the components will add up to the total
what is current like in series circuits
it is the same everywhere
the size of the current is determined by the total pd and resistance
what is resistance like in a series circuit
the total resistance is the sum of the resistance in the components
why is the total resistance in series circuit the sum of the resistance in components
because the components have to share the potential difference (voltage)
describe the appearance of a parallel circuit
it is multiple loops where each component is separately connected
what is potential difference (voltage) like in parallel circuits
there is the same amount of voltage for everything - the pd is the same across all components
what is current like in parallel circuits
it is shared - the total current flowing in the circuit is equal to the total currents through separate loops (components)
How do work out Rt for a parallel circuit
1/Rt = 1/R1 + 1/R2
then flip answer to get Rt/1
what is static electricity caused by
friction
What happens when static electricity is formed
- insulating materials are rubbed together
- electrons will transfer to one of the materials (they are oppositely charges)
What happens with a polythene rod
gains electrons - becoming negatively charged
What happens to a acetate rod
it loses electrons - becoming positively charged
why do insulators not lose its charge
because they don’t have free electrons
why does static electricity form sparks
because the potential difference gets large enough to jump across the gap between the charged object and earth
opposite charges…
attract
Same charges…
repel
What will happen to the total resistance in a parallel circuit if you add a resistor
the total resistance will decrease because the current has increased
What is the equation for voltage current and resistance
V= IR
