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Flashcards in 2 Deck (134):
1

What are good conductors of electricity?

Metals

2

Why are metals good conductors of electricity?

Electrons can easily flow through metals

3

What are good insulators?

Plastic
Glass

4

Why are plastic and glass good conductors?

Electrons cannot move through them

5

What materials does static electricity work with?

Insulators

6

Why would a child's hair stand up after going down a plastic slide?

Electrons move from the child onto the plastic when he sides down -child now has positive charge
The hair is positive so hairs repel each other and stand on end

7

How would a someone reduce the static electricity on their body?

Touch a metal object and electrons will move onto them to neutralise the charge

8

What is a cell?

1 battery

9

What is a battery in a circuit?

2 cells

10

What happens if you close a switch on a series circuit?

The cell pushes out electrons as it turns on
Electrons travel around the circuit

11

What is the flow of electrons called In a circuit?

Current

12

What do the electrons do?

Carry energy to appliances in the circuit

13

What is a series circuit?

No branches so electrons have to go in one direction

14

What happens if the switch is opened?

Electrons cannot flow so the current stops
Electrons no longer give appliances energy so appliances stop working

15

Why is the unit of current

Ampere (A)

16

How do we measure current

With an ammeter

17

What does the ammeter do?

Counts the number of electrons passing through every second to be able to work out the current

18

What happens to current in a series circuit ?

It is never used up
Current is the same throughout the circuit

19

What do parallel circuits have that series don't?

Branches

20

What happens to current in a parallel circuit?

The current splits at the branches and then rejoins to equal the full current

21

How does a light bulb light up in a circuit?

Electrons leaving cell carry energy
They give energy to bulb
Return back to cell with no energy

22

What is potential difference?

Energy that a cell gives to the current

23

What does potential difference tell us about appliances?

How much energy is used by the components

24

How do we measure potential difference?

Voltmeter

25

What does the voltmeter measure?

The energy the electrons are carrying when they leave the cell

And

How much energy electrons are giving to components

26

What happens to potential difference in a series circuit?

Potential difference is the same throughout the circuit

27

Why are bulbs dimmer when there are 2 in series circuit ?

Potential difference is split

28

Why can one bulb be dimmer?

One bulb receives more energy

29

What is the potential difference in a parallel circuit?

Each branch equals the same potential difference as the cell

30

What happens if 2 cells point in opposite directions?

Potential difference cancels out

31

What happens if you have multiple cells in the same direction?

The potential difference adds up

32

What does resistance tell us?

Idea of the energy needed to move a current though a component

33

What is the unit of resistance?

Ohm

34

How do you calculate resistance ?

R= v
-
I


35

What are resistors designed for?

To have a resistance so electrons need a lot of energy to pass through them

36

How would you make a bulb dimmer with a resistor?

Adding a resistor uses up some of the energy so the bulb is dimmer

37

What happens to the current through a resistor when we increase potential difference?

The current moving through a resistor is directly proportional to the potential difference across the resistor

BUT only if the temperature is kept constant

38

What does a filament do in a bulb?

Tightly coiled wire gets extremely hot as an electric current passes through causing it to glow and pass out light

39

What happens when you change the potential difference of a filament bulb and measure the current ? Why?

Current through filament bulb is not directly proportional to potential difference because the bulb gets hot which causes resistance to increase

High temps cause atoms in filaments to vibrate more so electrons in current now collide more with atoms wasting energy

40

What is special about a diode?

Only lets current through in forward direction

41

What does an LED do?

Gives off light when current passes through it in the forward direction

42

What is special about LDR's?

High resistance in the dark and low resistance in the light

43

What happens to a thermistor when temperature increases?

Resistance decreases

44

What are the positives and negatives of filament bulbs?

Good- cheap to make and buy

Bad- low energy efficiency
Only last 1200 hours

45

What are the positives and negatives of fluorescent bulbs?

Good- cheap
Quite efficient
Bad - only for 10000 hours

46

What are the positives and negatives of light emitting diodes (LED)

Good- Efficient
Lasts for 50000 hours

Bad- expensive

47

How do you calculate current?

Charge
--------
Time

48

How do you calculate potential difference ?

Energy
-------
Charge

49

How do you work out the power of appliances?

Power (w) =. Energy (j)
------------
Time (s)

50

What is mains electricity?

Alternating current

51

What does a cell give out? What type of current

Direct current

52

How do you work out the frequency of a wave ?

Frequency = 1/ time interval

53

What are wires in cables made of and why?

Copper because they're good conductors of electricity

54

Why is the coating of wire made of plastic ? Why is it used?

Does not conduct electricity so stops us from getting electrocuted

55

Name the 3 wires in 3 pin plugs? What do they do?

Blue - neutral
Brown - live
Striped- earth

56

Where do the wires go in a 3 pin plug?

bRown- right
bLue- left
sTriped - top

57

What does an earth wire do?

Stop us from getting electric shocks

Metal case attached to earth cable which is connected to ground by a rod
If fault causes the metal case becomes live
Big current flows through the case to the ground and causes fuse to melt shutting off the current

58

Why is a fuse? What does it do?

Thin piece of wire which conducts electricity
If current it too high the wire melts and current is cut preventing electrocution

59

How do you know which fuse is best?

Match the fuse to the appliance (slightly bigger)

60

What does a residual current circuit breaker do?

Detects difference between current in live and neutral wires

Shuts down current rapidly

61

What was the plum pudding model?

Region of positive charge with negative charges scattered in it

62

What was the nuclear model of an atom?

Positive nucleus with negative electrons surrounding

63

What do neutrons do?

Stop protons repelling each other

64

What is an isotope ?

Same number of protons different number of neutrons

65

What does it mean if an atom is radio active ?

Release radiation from its nucleus - decayed

66

Why can't you predict radioactive decay?

Totally random process - can't speed up or slow down

67

What does an alpha particle contain?

2 protons and 2 neutrons

68

What is a beta particle ?

Electrons produced in the nucleus and released

69

What is gamma radiation?

High energy electromagnetic wave

70

What were the results of the alpha scattering experiment?

Most alpha particles went straight through gold foil so most of an atom is empty space
Showed plum pudding model was wrong

Some particles bounces back - each atom must have small but heavy positive centre - repels

71

What is an alpha particles range in air?

5 cm before colliding with air particles

72

What is a beta particles range in air?

20cm in air

73

What is gamma radiations range in air?

Several metres

74

What is alpha particles penetrating power?

Stopped by a single sheet of paper

75

What is beta particles penetrating power?

Stopped by few mm of aluminium

76

What is gamma radiations penetrating power ?

Several cm of lead to stop

77

What is an ion?

When atoms lose or gain electrons

78

What is the ionising power of radiation particles?

Alpha- very strongly ionising
Beta - white strong
Gamma- weak

79

How does radiation travel ?

Straight lines

80

How does radiation travel in a magnetic field

Gamma- passes in straight line (no charge)
Beta- deflected strongly (negative)
Alpha- deflected in opposite direction (positive charge) but not strongly as they are heavy

81

What is alpha radiation used for? How do they work?

Smoke detectors

Radioactive element releases alpha radiation
It's is very strongly ionising so when it collides with air particles it makes them charged (ions)
Ions move to oppositely charges plate and crates small current between plates
Smoke particles attach to ions and atom them from moving
Reduces current and sets off alarm

82

What is a use of beta radiation? How is it made?

Producing aluminium

Beta radiation passes through aluminium and is detected on other side
The rollers roll the aluminium to the correct thickness and this is tested by the amount of beta radiation let through

83

What is a use of gamma radiation? How are they used?

Medical tracers

Radioactive dye is absorbed by tumour
Dye emits gamma radiation
Gamma radiation passes through body and can be detected on a scanner

84

How can gamma radiation treat cancer?

Gamma radiation is absorbed by cancer cells and kills them

85

What is half life?

Average time it takes for half of the nuclei to decay

86

What is background radiation caused by?

Radioactive rock
Food
Drinks
Medical
Nuclear weapons
Buildings and the ground

87

What is nuclear fission?

When the nucleus of an atom splits

88

What is nuclear fission used for?

Generate electricity In nuclear power stations

89

What elements are used in nuclear fission?

Uranium
Plutonium

90

How does nuclear fission occur?

Uranium or plutonium hit by a neutron
Nucleus splits into two smaller nuclei (radioactive)
Two or three more neutrons released
Chain reaction

91

What is nuclear fusion?

Two atomic nuclei joint to make a large nucleus

92

Where does nuclear fission occur?

Suns and stars to release energy

Starts begin life as a cloud of dust and hydrogen gas
Gravity pulls them together causing gas atoms to get hot
Forms a protostar

93

What is the life cycle of a star if the stars the same size as the sun?

Protostar
Main sequence star
Red giant
White dwarf
Black dwarf

94

What happens if a star is bigger than our sun?

Protostar
Main sequence
Red super giant
Supernova
Neutron star or black hole

95

Why isn't nuclear fusion used in power stations ?

Requires very high temperatures

96

What happens when two objects interact ?

Forces they exert on eachother are equal and opposite

97

What is the resultant force?

When a number of forces acting at a point can be replaced by a single force which has the same effect on the motion as the original forces al acting together

98

What can a resultant force do to an object?

Change its state of rest or motion

99

What happens if the resultant force on a stationary object is 0?

The object will remain stationary

100

What happens if the resultant force on a stationary object is not 0?

Object will accelerate in direction of resultant force

101

If resultant force acting on a moving force Is 0?

Object will move at same speed at same direction

102

What if resultant force on a moving object is not 0?

Object will accelerate in direction of resultant force

103

How do you calculate resultant force?

Force = mass x acceleration

104

What does the gradient of a distance time graph represent ?

Speed

105

What is velocity?

An objects speed in a given direction

106

How do you calculate acceleration?

Acceleration = change in velocity
------------------
Time

107

What does the gradient of a velocity time graph represent ?

Acceleration

108

What happens when a vehicle travels at a steady speed?

Resistive forces balance the driving force

109

What happens to the breaking force as speed increases ?

A greater breaking force is needed to stop in a certain distance

110

What is the stopping distance of a vehicle ?

Thinking distance + breaking distance

111

How can a drivers reaction time be affected ?

Tiredness
Drugs
Alcohol

112

What happens when breaks are applied ?

Work done by the friction force between the brakes and the wheel reduces kinetic energy of the wheel increases temp

113

What can vehicles breaking distance be affected by?

Adverse road and weather conditions
Poor vehicle conditions.

114

The faster an object moves through a fluid ....

The greater he frictional force that acts on it

115

Why will an object falling through a fluid initially accelerate ?

Due to the force of gravity

116

What is it called when an object falling through a fluid reaches a resultant force of 0?

Terminal velocity

117

How do you calculate the weight of an object?

Mass x gravitational field strength (10 n)

118

What can a force do to an object?

Change its shape

119

When happens when a force is applied to an elastic object ?

Object stretches and stores elastic potential

120

If An object is able to recover to its original shape when is elastic potential energy stored?

When woke is done on the object to change its shape

121

How do you work out the force applied to an elastic object?

F= spring constant x extension

122

What is work done?

When a force causes an object to move through a distance

123

How do you calculate work done?

W = force x distance

124

What is the unit of work done?

Joules

125

What happens when work is done?

Energy is transferred

126

What does power equal ?

P = energy
---------
Time

127

How do you calculate gpe?

Mass x gravitational field strength x height

128

How do you calculate kinetic energy?

1/2 x mass x velocity2

129

How do you calculate momentum ?

Mass x velocity

130

What is the conservation of momentum?

In a closed system the total momentum before an event = total momentum after an event

131

What are car safety features ? Name some

They absorb kinetic energy reducing momentum slowly. Reduces injury

Air bags
Crumple zone
Seat belt
Side impact bars

132

How do air bags work?

Air bags cushion the heard absorbing kinetic energy . Contains air which is slowly released

133

How do crumple zones and side impact bars work?

Gradually crush reducing momentum slowly

134

How do seat belts work?

Seat belt stops person from smashing into seat
Momentum reduces gradually