Topic 8 Flashcards
1
Q
Work done
A
When energy is transferred from one store to another
2
Q
GPE
A
The energy and object has due to its height in a gravitational field
3
Q
The gravitational field strength on the eart is
A
10
4
Q
GPE is more on
A
Gas giants
5
Q
GPE is less on the
A
Moon
6
Q
Kinetic energy is
A
The energy an object had as a result of its mass and speed
7
Q
Useful energy
A
The energy that is transferred to the place where it is wanted in the form that it is needed
8
Q
Wasted energy
A
The energy that is not useful for the intended purpose and is dissipated to the surroundings
9
Q
Reducing energy loss
A
Lubrication
Insulation
10
Q
Power
A
The rate of energy transfer or the rate of work done
11
Q
Efficiency
A
The ratio of the useful power or energy transfer output from a system to its total power or energy transfer input
12
Q
A force is
A
A push or pull that acts on an object due to the interaction with another object
13
Q
Contact forces include
A
Friction
Air resistance
Tension
Reaction force
14
Q
Non contact forces
A
Gravity
Electrostatic
Magnesium
15
Q
Function of fixed resistor
A
Limits the flow of current
Resistance cannot be changed
16
Q
Thermistor
A
A resistor which resistance depends on its temperature
As temp increases resistance decreases
17
Q
LDR
A
Resistance depends on light intensity
18
Q
Motor
A
Device that converts electrical energy to mechanical energy
19
Q
Diode
A
Allows current to flow in only one direction
20
Q
LED
A
Diode that emits light when a current passes through it
21
Q
Ammeter
A
Used to measure the current in a circuit
22
Q
Voltmeters
A
Use to measure potential difference in a circuit
23
Q
Ammeter is always connected in a
A
Series
24
Q
Voltmeter is always connected in a parallel
A
25
Direction of current flow
From positive to negative power supply
26
Potential difference
The amount of energy transferred per unit of charge passing through terminals
27
Current
The rate of flow of charge
28
When two or more resistors are connected in series the total resistance is
Teh sum of the resistors
29
In a series circuit the voltage of a power supply is
Shared between all components
30
When two or more resistors are connected in parallel
The net resistance decreases as more charge is allowed to flow overall
31
Advantages of parallel
The components can be individually controlled
If one component stops working the others will continue to function
32
Current in a series circuit
The current is the same at all points
33
Current in a parolee circuit
The current at junctions
34
Potential difference in a series circuit
Voltage of power supply is shared between components
35
In a parallel circuit teh voltage across each component is teh same
36
In a parell circuit the total resistance is
Less than teh resistance of individuals components
37
The current is what variable
Independent
38
Teh voltage is what variable
Dependent
39
What factors choose how much heat is produced
Current
Resistance
40
How is heat produced in a circuit
collisions between:
Electrons flowing in the conductor, and
The lattice of atoms within the metal condu
When the electrons collide they lose energy giving it to the ions cause in them to vibrate more and heat up
41
Direct current
A current that is steady constantly flowing in the same direct in a circuit from positive to negative
42
Alternating current
A current that continuously changes its direction going back and forth around a circuit
43
Mains AC
Generated by power stations
Transported through the national grid
44
Mains AC frequency
50Hz
45
Mains AC potential difference
230v
46
Live wire colour
Brown
47
Neutral wire colour
Blue
48
Earth wire colour
Green and yellow stripey
49
The live wire function
Carries alternating potential difference from the supply to the circuit
50
The neatrul wire
Forms the opposite end of the circuit to the live wires to complete the circuit
51
Earth wire function
Safety wire that provides low resistance path to earth
52
Neutral wire and earth wire voltage
0
53
Ends of magnets are called
Poles
54
Magnetic metals
Iron
Colbalt
Nickle
55
Permanent magnets
Produce its own magnetic field
56
Induced magnets
When a magnetic material is placed into a magnetic field the material can temporarily be turned into a magnet
When it is removed it loses its magnetism
57
Magnetic field
The region around a magnet where a force acts on another magnet or on a magnetic material (such as iron, steel, cobalt and nickel)
58
Magnetic field around a bar magnet
The field is strongest at the poles
59
Strength of magnetic field factors
Size of current
Distance from long straight conductor
60
How to increase strength of magnetic field around wire
Coil it to form solenoid
61
The motor effect occurs when
A wire with current flowing through it is placed inside a magnetic field and experiences a force
62
Factors effecting em induction
The speed at which the wire, coil or magnet is moved
The number of turns on the coils of wire
The size of the coils
The strength of the magnetic field
63
speed at which the wire, coil or magnet is moved:
Increasing the speed will increase the rate at which the magnetic field lines are cut
This will increase the induced potential difference
64
The number of turns on the coils in the wire:
Increasing the number of turns on the coils in the wire will increase the potential difference induced
This is because each coil will cut through the magnetic field lines and the total potential difference induced will be the result of all of the coils cutting the magnetic field lines
65
. The size of the coils:
Increasing the area of the coils will increase the potential difference induced
This is because there will be more wire to cut through the magnetic field lines
66
The strength of the magnetic field:
Increasing the strength of the magnetic field will increase the potential difference induced
67
Transformers
A transformer is an electrical device that can be used to increase or decrease the potential difference of an alternating current
This is achieved using the generator effect
68
Generator effect
The generator effect occurs whenever a potential difference is induced across a conductor which is experiencing a change in an external magnetic field
69
Structure of transformer
A primary coil
A secondary coil
An iron core
70
How a transformer works
The iron core is easily magnetised, so the changing magnetic field passes through it
As a result, there is now a changing magnetic field inside the secondary coil
This changing field cuts through the secondary coil and induces a potential difference
As the magnetic field is continually changing the potential difference induced will be alternating
The alternating potential difference will have the same frequency as the alternating current supplied to the primary coil
If the secondary coil is part of a complete circuit it will cause an alternating current to flow
71
Role of transformers
Change size of alternating voltage
72
Apparatus for measuring density of irregular objects
Eureka can
73
Specific heat capacity
The amount of energy required to raise the temperature of 1kg of th e substance by 1c
74
Specific heat latent
The amount of thermal energy required to change the state of 1 kg of a substance with no change in temperature
75
Specific latent heat fusion
The thermal energy required to convert 1 kg of solid to liquid with no change in temperature
76
Absolute zero
-273c
77
Absolute zero definition
The temperature at which molecules in a substance have zero kinetic energy
78
Hooks law
The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality
