P4 Electric circuits (paper 1) Flashcards
1
Q
What makes up electricity
A
electrons
2
Q
define current
A
the rate of flow of charge
3
Q
What is the unit for current
A
Amps (A)
4
Q
What is voltage
A
the amount of energy per charge
5
Q
What is the unit for voltage
A
Volts (V)
6
Q
What does resistance do
A
slow the current down, resisting the flow of charge
7
Q
What is resistance measured in
A
Ohms (Ω)
8
Q
Define ohms law in a sentence
A
Voltage and current are directly proportional (r=v/i)
9
Q
When does more charge pass around a circuit
A
when a larger current flows
10
Q
A
ammeter
11
Q
A
bulb
12
Q
A
buzzar
13
Q
A
cell
14
Q
A
diode
15
Q
A
LDR
16
Q
A
LED
17
Q
A
motor
18
Q
A
resistor
19
Q
A
switch
20
Q
A
thermistor
21
Q
A
variable resistor
22
Q
A
voltmeter
23
Q
A
battery
24
Q
What makes something and ohmic conductor
A
its current flowing through is directly proportional to the potential difference (voltage) across it
25
Give an example of an ohmic conductor
a wire
a resistor
26
describe what a graph of a wire would be like
the voltage and current are directly proportional
27
Why does resistance change in a filament bulb
because of the heating effect
28
What happens in the heating affect
- collisions between electrons and metal ions
- friction caused
- causes heat which
- increases resistance
29
what does the resistance of a diode depend on
the direction of the current
30
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
31
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
32
what I-V characteristics do linear components have
straight line
33
what I-V characteristics do non-linear components have
a curved line
34
describe the relationship of an I-V graph of a filament bulb
It starts directly proportional, overtime the gradient slowly decreases - the resistance increases
35
Why does the resistance start to increase in an I-V graph of a filament bulb
because of the heating effect
36
in an I-V graph how does resistance and gradient relate
as gradient goes down (flatter) resistance goes up
37
What is LDR short for
Light dependent resistor
38
what is an LDR
a resistor that is dependent on the intensity of light
39
How does light affect the resistance in an LDR
as light intensity increases resistance decreases (lurd)
40
What does resistance in a thermistor depend on
temperature
41
How does temperature affect the resistance in a thermistor
As temperature increases resistance decreases (turd)
42
What type of graph is this
a diode I-V graph
43
What type of graph is this
a filament bulb I-V graph
44
What type of graph is this
A wire I-V graph
45
What type of graph is this
An LDR graph
46
What type of graph is this
a thermistor graph
47
what can you use LDRs and thermistors in
sensing circuits
48
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
49
What path does electricity take
the one with the least resistance
50
Describe the appearance of series circuits
They are one loop and all of the components are connected in a line, end to end
51
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
52
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
53
what is resistance like in a series circuit
the total resistance is the sum of the resistance in the components
54
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)
55
describe the appearance of a parallel circuit
it is multiple loops where each component is separately connected
56
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
57
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)
58
How do work out Rt for a parallel circuit
1/Rt = 1/R1 + 1/R2
then flip answer to get Rt/1
59
what is static electricity caused by
friction
60
What happens when static electricity is formed
- insulating materials are rubbed together
- electrons will transfer to one of the materials (they are oppositely charges)
61
What happens with a polythene rod
gains electrons - becoming negatively charged
62
What happens to a acetate rod
it loses electrons - becoming positively charged
63
why do insulators not lose its charge
because they don't have free electrons
64
why does static electricity form sparks
because the potential difference gets large enough to jump across the gap between the charged object and earth
65
opposite charges...
attract
66
Same charges...
repel
67
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
68
What is the equation for voltage current and resistance
V= IR
69
Explain why adding resistors in parallel decreases the total resistance
- multiple paths for charge to flow
- total current is greater for the same pd when more resistors are added
