4.2 Electricity Flashcards
(79 cards)
1
Q
What must a closed circuit include for an electrical charge to flow through?
A
A source of potential difficulties
2
Q
What is electric current?
A
A flow of electric electrical charge
3
Q
What is the size of the elephant current?
A
The rate of flow of electrical charge
4
Q
What is the equation for charge flow?
A
Charge flow = current x time
5
Q
What is the symbol for charge flow?
A
Q
6
Q
What is the symbol for current?
A
I
7
Q
What is charge flow measured in?
A
Coulombs C
8
Q
What is current measured in?
A
Amps A
9
Q
Where does the current have the same value?
A
Anany point in a single closed loop
10
Q
What does the current through a component depend on?
A
The resistance of the component and the potential difference across the component
11
Q
What happens to the current if the greater the resistance of the component?
A
The smaller the cure for a given potential difference across the component
12
Q
What is the equation for potential difference ?
A
Potential difference = current x resistance
13
Q
What is the symbol for potential difference?
A
V
14
Q
What is the symbol for resistance?
A
R
15
Q
What is potential difference measured in?
A
Volts V
16
Q
What is resistance measured in ?
A
Ohms
17
Q
What is the current through an ohmic conductor directly proportional to?
A
The potential diff across the resistor
18
Q
What does the current through an ohmic conductor directly proportional to the potential difference mean?
A
The resistance remains constant the current changes
19
Q
What components are the resistors not constant?
A
Lamps diodes thermistors and LDRs
20
Q
What do the resistance lamps diodes thermistors and LDRs change with?
A
The current through the component
21
Q
When does the resistance of a filament lamp increase?
A
As the temperature of the filament increases
22
Q
How does the cure through a diode flow?
A
In one direction only
23
Q
When the diode have a very high resistance?
A
In the reverse direction
24
Q
When does the resistance of a thermistors decrease?
A
As the temperature increases
25
When does the resident of LDRs decrease?
As light intensity increases
26
What is the application of thermistors in a circuit?
Thermostat is required
27
What is the application of LDRs in circuits?
Switching lights on when it gets dark
28
Explain the design and use of a circuit to measure the resistance of a component by measuring the current through and potential difference across the component
an ammeter to measure current, a voltmeter to measure voltage, and a known resistor in series with the component whose resistance is being measured
29
What are the 2 ways in joining electrical components?
In series and parallel
30
What are some properties for components connected in series?
There is the same current through each component
The total potential difference of the power supplied is shared between the components
The total resistance of two components is the sum of the resistance of each component
31
What the equation for total resistance?
R1 + R2
32
What the properties for components connected in parallel?
The potential difference across each component is the same
The total current through the whole circuit is the sum of the currents through the separate components
The total resistance of two resistors is less than the resistance of the smallest individual resistor
33
What is the difference between a series and parallel circuit?
In a series circuit, components are connected in a single loop, meaning there's only one path for current to flow. In contrast, a parallel circuit has multiple paths for current to flow, with components connected across different branches
34
Explain why adding resistors in series increases the total resistance whilst adding resistors in parallel decreases the total resistance
Adding resistors in series increases total resistance because it effectively adds more obstacles for the current to flow through, while adding resistors in parallel decreases total resistance because it provides more paths for the current to take.
35
What is mains electricity?
An ac supply
36
What is the frequency of the UKs domestic electricity supply?
50hz and is about 230v
37
What is the difference between direct and alternating potential difference?
Direct potential differences produce a constant electric current that flows in one direction, while alternating potential differences produce an alternating current that changes direction regularly.
38
What are most electrical appliances connected to the mains by?
Using three core cable
39
Why is the insulation covering each wire colour coded?
For easy identification
40
What does the brown wire mean?
Live wire
41
What does the blue wire mean?
Neutral wire
42
What does the green and yellow stripes wire mean?
Earth wire
43
What does the live wire carry?
The alternating potential difference from the supply
44
What the neutral wire do?
Completes the circuit
45
What does the earth wire do?
It is a safety wire to stop the appliance becoming live
46
What is the potential difference between the live wire and earth?
2e0v
47
When does the earth wire carry a charge?
It only carries a current if there is a fault
48
Why might the live wire may be dangerous even when a switch in the mains circuit is open?
e it maintains a high voltage potential, and if someone touches it, their body can complete a circuit to the ground, causing an electric shock
49
What are the dangers of providing any connectivity between the live wire and earth?
creates a short circuit, which can be extremely dangerous, causing potential for electric shock, fire, and damage to electrical equipment
50
How is the power transfer in any circuit device related to the potential difference across it and the current through it and to the energy changes over time?
The power transferred is equal to the product of the potential difference and the current
If either p.d. or current increases, the power increases
51
What is the equation for power1?
Potential difference x current
52
What is another equation for power?
Current squared x resistance
53
What are everyday electrical appliances designed to bring ?
Bring about energy transfers
54
What does the amount of energy an appliance transfers depend on ?
How long the appliance is switched on for and the power of the appliance
55
How do different domestic appliances transfer energy from batteries or ac mains to the kinetic energy of electric motors or the energy of heating devices?
through electrical circuits
56
When is work done?
When charge flows in a circuit
57
What is the equation for energy transferred?
Power x time
58
What is another equation for energy transferred?
Charge flow x potential difference
59
How is the power of a circuit device related to the potential difference across it and the current through it?
The power of a circuit device is directly related to the potential difference
60
How is the power of a circuit device related to the energy transferred over a given time?
The power of a circuit device is directly related to the amount of energy transferred over a given time
61
What is the national grid ?
A system of cables and transformers linking power stations to consumers
62
Where is electrical power transferred from?
Power stations to consumers using the national grid
63
What are step up transformers used to increase ?
The potential difference from the power station to the transmission cables
64
What are step down transformers used to decrease?
The potential difference to a much lower value , the potential difference for domestic use
65
Why is the national grid system an efficient way to transfer energy?
it uses high voltage, low current transmission, minimizing energy loss due to heat in the transmission lines
66
What happens to certain insulating materials when rubbed against each other?
They became electrically charged
67
What happens to the material that gains electrons?
It becomes negatively charged
68
What happens to the material that loses electrons?
A
Becomes an equal positive charge
69
What happens when 2 electrically charged objects are brought close together?
They exert a force on each other
70
Do 2 charges that carry the same charge attract or repel?
Repel
71
Do 2 charges that carry diff charges attract or repel?
Attract
72
What are attraction and repulsion examples of?
Non contact forces?
73
Describe the productions of static electricity and sparking by rubbing surface surfaces
when friction causes a transfer of electrons between materials, resulting in one material becoming negatively charged (gaining electrons) and the other becoming positively charged (losing electrons)
74
Describe evidence that charged objects exert forces of attraction or repulsion on one another when not in contact?
experiments with charged rods and balls, where their movements reveal the presence of either attraction or repulsion.
75
Explain how the transfer of electrons between objects can explain the phenomena of static electricity?
Static electricity arises from the transfer of electrons between objects, primarily through friction
76
What does a charged object create?
An electric field around itself
77
Where is the electrical field the strongest?
Closer to the charged object
78
What happens to the electric field when the charged object is further away ?
The weaker the field
79
What happens when a second charged object is placed in the field ?
It experiences a force and as the force gets stronger as the distance between the objects decrease
