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19/04/23
AQA Additional ScienceAQA Additional Science
W Richards
Physics 2Physics 2A slideshow that covers the entire AQA
2006 Syllabus Physics 2 Module
19/04/23Distance, Distance, Speed and Speed and
TimeTimeSpeed = distance (in metres)
time (in seconds)
D
TS
1) Seb walks 200 metres in 40 seconds. What is his speed?
2) Lucy covers 2km in 1,000 seconds. What is her speed?
3) How long would it take Freddie to run 100 metres if he runs at 10m/s?
4) Sue travels at 50m/s for 20s. How far does he go?
5) Hannah drives her car at 85mph (about 40m/s). How long does it take her to drive 20km?
19/04/23Speed vs. VelocitySpeed vs. Velocity
Speed is simply how fast you are travelling…
Velocity is “speed in a given direction” (a “vector quantity”)…
This car is travelling at a speed of 20m/s
This car is travelling at a velocity of 20m/s east
19/04/23
AccelerationAcceleration V-U
TA
Acceleration = change in velocity (in m/s)
(in m/s2) time taken (in s)
1) A cyclist accelerates from 0 to 10m/s in 5 seconds. What is her acceleration?
2) A ball is dropped and accelerates downwards at a rate of 10m/s2 for 12 seconds. How much will the ball’s velocity increase by?
3) A car accelerates from 10 to 20m/s with an acceleration of 2m/s2. How long did this take?
4) A rocket accelerates from 1,000m/s to 5,000m/s in 2 seconds. What is its acceleration?
19/04/23
Velocity-time graphsVelocity-time graphs
80
60
40
20
0 10 20 30 40 50
Velocity
m/s
T/s
1) Upwards line =
2) Horizontal line =
3) Upwards line =
4) Downward line =
19/04/23
80
60
40
20
0
1) How fast was the object going after 10 seconds?
2) What is the acceleration from 20 to 30 seconds?
3) What was the deceleration from 30 to 50s?
4) How far did the object travel altogether?
10 20 30 40 50
Velocity
m/s
T/s
19/04/23Balanced and unbalanced Balanced and unbalanced forcesforces
Consider a camel standing on a road. What forces are acting on it?
Weight
Reaction
These two forces would be equal – we say that they are BALANCED. The camel doesn’t move anywhere.
19/04/23Balanced and unbalanced Balanced and unbalanced forcesforces
What would happen if we took the road away?
Weight
Reaction
The camel’s weight is no longer balanced by anything, so the camel falls downwards…
19/04/23
Introduction to ForcesIntroduction to ForcesA force is a “push” or a “pull”. Some common examples:
Weight (mg) – pulls things towards the centre of the Earth
Air resistance/drag – a contact force that acts against anything moving through air or liquid
Upthrust – keeps things afloat
_____ – a contact force that acts against anything moving
19/04/23
Air ResistanceAir ResistanceAir resistance is a force that opposes motion through air. The quicker you travel, the bigger the air resistance:
The same applies to a body falling through a liquid (called “drag” or “upthrust”).
19/04/23Balanced and unbalanced Balanced and unbalanced forcesforces
19/04/23Balanced and unbalanced Balanced and unbalanced forcesforces
1) This animal is either ________ or moving with _____ _____…
4) This animal is…
2) This animal is getting _________…
3) This animal is getting _______….
19/04/23
Resultant ForceResultant ForceCalculate the resultant force of the following:
500N 100N 700N 600N
700N 700N
200N
800N 800N
100N
50N
19/04/23
Force and accelerationForce and acceleration
If the forces acting on an object are unbalanced then the object will accelerate, like these wrestlers:
Force (in N) = Mass (in kg) x Acceleration (in m/s2)
F
AM
19/04/23
Force, mass and accelerationForce, mass and acceleration
1) A force of 1000N is applied to push a mass of 500kg. How quickly does it accelerate?
2) A force of 3000N acts on a car to make it accelerate by 1.5m/s2. How heavy is the car?
3) A car accelerates at a rate of 5m/s2. If it weighs 500kg how much driving force is the engine applying?
4) A force of 10N is applied by a boy while lifting a 20kg mass. How much does it accelerate by?
F
AM
19/04/23
Terminal VelocityTerminal VelocityConsider a skydiver:
1) At the start of his jump the air resistance is _______ so he _______ downwards.
2) As his speed increases his air resistance will _______
3) Eventually the air resistance will be big enough to _______ the skydiver’s weight. At this point the forces are balanced so his speed becomes ________ - this is called TERMINAL VELOCITY
Words – increase, small, constant, balance,
accelerates
19/04/23Terminal Terminal VelocityVelocity
Consider a skydiver:
4) When he opens his parachute the air resistance suddenly ________, causing him to start _____ ____.
5) Because he is slowing down his air resistance will _______ again until it balances his _________. The skydiver has now reached a new, lower ________ _______.
Words – slowing down, decrease, increases, terminal
velocity, weight
19/04/23Velocity-time graph for terminal Velocity-time graph for terminal velocity…velocity…
Velocity
Time
Speed increases…
Terminal velocity reached…
Parachute opens – diver slows down
New, lower terminal velocity reached
Diver hits the ground
On the Moon
19/04/23
Stopping a car…Stopping a car…
Braking distance
Too much alcoholThinking
distance
(reaction time)
Tiredness
Too many drugs
Wet roads
Driving too fast
Tyres/brakes worn out
Icy roads
Poor visibility
19/04/23
MomentumMomentumAny object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula:
Momentum = Mass x Velocity (in kgms-1) (in kg) (in ms-
1)
P
VM
What is the momentum of the following?
1) A 1kg football travelling at 10ms-1
2) A 1000kg Ford Capri travelling at 30ms-1
3) A 20g pen being thrown across the room at 5ms-1
4) A 70kg bungi-jumper falling at 40ms-1
19/04/23
Force and momentumForce and momentumNewton’s second law of motion says that the force acting on an object is that object’s rate of change of momentum. In other words…
mv
TF
Force = Change in momentum Time(in N)
(in kgm/s)
(in s)
For example, David Beckham takes a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:
1) The change in momentum of the ball (its impulse),
2) The speed the ball moves away with
Also called “impulse”
19/04/23
Example questionsExample questions1) Ben likes playing golf. He strikes a golf ball with a
force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.
2) Nick thinks it’s funny to hit tennis balls at Tom. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.
3) Dan takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If his foot was in contact with the ball for 0.1 seconds calculate the force he applied to the ball.
4) Simon strikes a 200g golf ball away at 50m/s. If he applied a force of 50N calculate how long his club was in contact with the ball for.
19/04/23
Safety featuresSafety featuresLet’s use Newton’s Second Law to explain how airbags work:
mv
TF
Basically:
1) The change in momentum is the same with or without an airbag
2) But having an airbag increases the time of the collision
3) Therefore the force is reduced
19/04/23
Weight vs. MassWeight vs. MassEarth’s Gravitational Field Strength is 10N/kg. In other
words, a 1kg mass is pulled downwards by a force of 10N.
W
gM
Weight = Mass x Gravitational Field Strength
(in N) (in kg) (in N/kg)
1) What is the weight on Earth of a book with mass 2kg?
2) What is the weight on Earth of an apple with mass 100g?
3) Dave weighs 700N. What is his mass?
4) On the moon the gravitational field strength is 1.6N/kg. What will Dave weigh if he stands on the moon?
19/04/23
Stopping a car…Stopping a car…
Braking distance
Too much alcoholThinking
distance
(reaction time)
Tiredness
Too many drugs
Wet roads
Driving too fast
Tyres/brakes worn out
Icy roads
Poor visibility
19/04/23
Work doneWork done
When any object is moved around work will need to be done on it to get it to move (obviously).
We can work out the amount of work done in moving an object using the formula:
Work done = Force x distance moved
in J in N in m
W
DF
19/04/23
Example questionsExample questions1. Bori pushes a book 5m along the table with a force of
5N. He gets tired and decides to call it a day. How much work did he do?
2. Alicia lifts a laptop 2m into the air with a force of 10N. How much work does she do?
3. Martin does 200J of work by pushing a wheelbarrow with a force of 50N. How far did he push it?
4. Chris cuddles his cat and lifts it 1.5m in the air. If he did 75J of work how much force did he use?
5. Carl drives his car 1000m. If the engine was producing a driving force of 2000N how much work did the car do?
19/04/23
Elastic Potential EnergyElastic Potential Energy
Elastic potential energy is the energy stored in a system when work is done to change its shape, e.g:
19/04/23
Kinetic energyKinetic energyAny object that moves will have kinetic energy.
The amount of kinetic energy an object has can be found using the formula:
Kinetic energy = ½ x mass x velocity squared
in J in kg in m/s
KE = ½ mv2
19/04/23
Example questionsExample questions
1) Nicole drives her car at a speed of 30m/s. If the combined mass of her and the car is 1000kg what is her kinetic energy?
2) Shanie rides her bike at a speed of 10m/s. If the combined mass of Shanie and her bike is 80kg what is her kinetic energy?
3) Dan is running and has a kinetic energy of 750J. If his mass is 60kg how fast is he running?
4) George is walking to town. If he has a kinetic energy of 150J and he’s walking at a pace of 2m/s what is his mass?
19/04/23
Random questions…Random questions…1) Sophie tries to run 100m in 12 seconds and succeeds. How fast
did she run?
2) Tommy accelerates at a rate of 2m/s2 for 3 seconds. If he started at 10m/s what was his final speed?
3) Charlie decides to lift his book up into the air. His book has a mass of 100g and he lifts it 50cm. Calculate the work done.
4) Lewis accelerates from 0 to 10m/s in 5 seconds. If his mass is 70kg how much force did his legs apply?
5) Rachel rides 1km at a speed of 20m/s. How long did the journey take?
6) Claire thinks it’s funny to push James with a force of 120N. If James has a mass of 60kg calculate his acceleration.
7) Lauren slams on the brakes on her bike and her brakes do 20,000J of work. If the combined mass is 100kg what speed was she travelling at?
8) Tom has a mass of 75kg. If he accelerates from 10 to 20m/s in 2s how much force did he apply?
19/04/23
Random questions…Random questions…9) Georgina amuses herself by throwing things at Sarah. If she
throws a ball with a speed of 20m/s and the distance between her and Sarah is 5m how long will it take to reach her?
10)Mr Richards throws calculators around the room with a force of 20N. If each calculator has a mass of 200g calculate the acceleration.
11)Sam has a mass of 70kg. What is his weight on Earth, where the gravitational field strength is 10N/kg?
12)Zak does some work by pushing a box around with a force of 1N. He does 5J of work and decides to call it a day. How far did he push it?
13)On the moon Matt might weigh 112N. If the gravitational field strength on the moon is 1.6N/kg what is his mass? What will he weigh on Earth?
14)Dan likes bird watching. He sees a bird fly 100m in 20s. How fast was it flying?
15)How much kinetic energy would Richard have if he travelled at a speed of 5m/s and has a mass of 70kg?
19/04/23
MomentumMomentumAny object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula:
Momentum = Mass x Velocity (in kgms-1) (in kg) (in ms-
1)
P
VM
What is the momentum of the following?
1) A 1kg football travelling at 10ms-1
2) A 1000kg Ford Capri travelling at 30ms-1
3) A 20g pen being thrown across the room at 5ms-1
4) A 70kg bungi-jumper falling at 40ms-1
19/04/23
Conservation of MomentumConservation of MomentumIn any collision or explosion momentum is conserved (provided that there are no external forces have an effect). Example question:
Two cars are racing around the M25. Car A collides with the back of car B and the cars stick together. What speed do they move at after the collision?
Mass = 1000kg
Mass = 800kg
Speed = 50ms-1 Speed = 20ms-1
Momentum before = momentum after…
…so 1000 x 50 + 800 x 20 = 1800 x V…
…V = 36.7ms-1
Mass = 1800kg
Speed = ??ms-1
19/04/23
Momentum in different directionsMomentum in different directionsWhat happens if the bodies are moving in opposite directions?
Speed = 50ms-1
Mass = 1000kg
Speed = 20ms-1
Mass = 800kg
Momentum is a VECTOR quantity, so the momentum of the second car is negative…
Total momentum = 1000 x 50 – 800 x 20 = 34000 kgms-1
Speed after collision = 34000 kgms-1 / 1800 = 18.9ms-1
19/04/23
Another exampleAnother example
Consider the nuclear decay of Americium-241:
Am24195
α42
If the new neptunium atom moves away at a speed of 5x105 ms-1 what was the speed of the alpha particle?
Np23793
19/04/23
More questions…More questions…1) A white snooker ball moving at 5m/s strikes a red ball and pots it.
Both balls have a mass of 1kg. If the white ball continued in the same direction at 2m/s what was the velocity of the red ball?
2) A car of mass 1000kg heading up the M1 at 50m/s collides with a stationary truck of mass 8000kg and sticks to it. What velocity does the wreckage move forward at?
3) A defender running away from a goalkeeper at 5m/s is hit in the back of his head by the goal kick. The ball stops dead and the player’s speed increases to 5.5m/s. If the ball had a mass of 500g and the player had a mass of 70kg how fast was the ball moving?
4) A gun has a recoil speed of 2m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g what speed does the bullet come out at?
19/04/23
Force and momentumForce and momentumNewton’s second law of motion says that the force acting on an object is that object’s rate of change of momentum. In other words…
mv
TF
Force = Change in momentum Time(in N)
(in kgm/s)
(in s)
For example, David Beckham takes a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:
1) The change in momentum of the ball (its impulse),
2) The speed the ball moves away with
Also called “impulse”
19/04/23
Example questionsExample questions1) Ben likes playing golf. He strikes a golf ball with a
force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.
2) Nick thinks it’s funny to hit tennis balls at Tom. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.
3) Dan takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If his foot was in contact with the ball for 0.1 seconds calculate the force he applied to the ball.
4) Simon strikes a 200g golf ball away at 50m/s. If he applied a force of 50N calculate how long his club was in contact with the ball for.
19/04/23
Safety featuresSafety featuresLet’s use Newton’s Second Law to explain how airbags work:
mv
TF
Basically:
1) The change in momentum is the same with or without an airbag
2) But having an airbag increases the time of the collision
3) Therefore the force is reduced
19/04/23
Static ElectricityStatic ElectricityStatic electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used:
+ -
+-
+
+-
-
-+
+
+
-
-
+
+
+-
-
-
19/04/23
Static ElectricityStatic Electricity
++
+ --
-
--
---
-
19/04/23
Van de Graaf generatorsVan de Graaf generators
19/04/23
Uses of Static – Smoke PrecipitatorsUses of Static – Smoke Precipitators
-
-
-
-
-
-
+ ++
Chimney
Negatively charged
plates
Positively charged
grid
19/04/23Uses and dangers of Static Uses and dangers of Static ElectricityElectricity
Find out how static electricity is used in the following:
1) Photocopiers
2) Paint sprayer
Find out how static electricity is dangerous in the following situations:
1) Fuel pipes
2) Hospitals
19/04/23
Circuit SymbolsCircuit Symbols
VA
Battery
Cell
Fuse
Resistor
LDR
Voltmeter
Ammeter
Variable resistor
Diode
Switch
Bulb
Thermistor
19/04/23
Electric CurrentElectric CurrentElectric current is a flow of negatively charged particles (i.e. electrons).
Note that electrons go from negative to positive-+ e-
e-
By definition, current is “the rate of flow of
charge”
19/04/23
Basic ideas…Basic ideas…Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____.
Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______, a unit named after Volta.
Resistance is anything that resists an electric current. It is measured in _____.
Words: volts, amps, ohms, voltage, ammeter, voltmeter
19/04/23
More basic ideas…More basic ideas…
If a battery is added the current will ________ because there is a greater _____ on the electrons
If a bulb is added the current will _______ because there is greater ________ in the circuit
19/04/23
Current in a series circuitCurrent in a series circuit
If the current here is 2 amps…
The current here will be…
The current here will be…
And the current here will be…
In other words, the current in a series circuit is THE SAME at any
point
19/04/23
Current in a parallel circuitCurrent in a parallel circuit
A PARALLEL circuit is one where the current has a “choice of routes”
Here comes the current…
And the rest will go down here…
Half of the current will go down here (assuming the bulbs are the same)…
19/04/23
Current in a parallel circuitCurrent in a parallel circuit
If the current here is 6 amps
The current here will be…
The current here will be…
The current here will be…
And the current here will be…
19/04/23
Some example questions…Some example questions…
3A
6A
19/04/23
Voltage in a series circuitVoltage in a series circuit
V
V V
If the voltage across the battery is 6V…
…and these bulbs are all identical…
…what will the voltage across each bulb be? 2V
19/04/23
Voltage in a series circuitVoltage in a series circuit
V
V
If the voltage across the battery is 6V…
…what will the voltage across two bulbs be?
4V
19/04/23
Voltage in a parallel circuitVoltage in a parallel circuit
If the voltage across the batteries is 4V…
What is the voltage here?
And here?
V
V4V
4V
19/04/23
SummarySummary
In a SERIES circuit:
Current is THE SAME at any point
Voltage SPLITS UP over each component
In a PARALLEL circuit:
Current SPLITS UP down each “strand”
Voltage is THE SAME across each”strand”
19/04/23
An example question:An example question:
V1
V2
6V
3A
A1
A2
V3
A3
19/04/23
Another example question:Another example question:
V1
V2
10V3A
A1
A2
V3
A3
19/04/23
Georg Simon Ohm 1789-1854
ResistanceResistance
Resistance is anything that will RESIST a current. It is
measured in Ohms, a unit named after me.
The resistance of a component can be calculated using Ohm’s Law:
Resistance = Voltage (in V)
(in ) Current (in A)
V
RI
19/04/23
An example question:An example question:
V
A
1) What is the resistance across this bulb?
2) Assuming all the bulbs are the same what is the total resistance in this circuit?
Voltmeter reads 10V
Ammeter reads 2A
19/04/23
More examples…More examples…
12V
3A
3A
6V
4V
2A
1A
2V
What is the resistance of these bulbs?
19/04/23
ResistanceResistance
Resistance is anything that opposes an electric current.Resistance (Ohms, ) = Potential Difference (volts, V)
Current (amps, A)
What is the resistance of the following:
1) A bulb with a voltage of 3V and a current of 1A.
2) A resistor with a voltage of 12V and a current of 3A
3) A diode with a voltage of 240V and a current of 40A
4) A thermistor with a current of 0.5A and a voltage of 10V
19/04/23
Resistors, bulbs and diodesResistors, bulbs and diodes
19/04/23
Current-Voltage GraphsCurrent-Voltage Graphs
Voltage on powerpack/V
Current/A Voltage/V
1210…0…-10-12
19/04/23
Current-voltage graphsCurrent-voltage graphsI
VI
V
I
V
1. Resistor 3. Diode
2. BulbCurrent increases in proportion to voltage
As voltage increases the bulb gets hotter and resistance increases
A diode only lets current go in one direction – it has very high resistance in the other direction
19/04/23
LDRs and ThermistorsLDRs and Thermistors
19/04/23
Two simple components:Two simple components:
2) Thermistor – resistance DECREASES when temperature INCREASES
1) Light dependant resistor – resistance DECREASES when light intensity INCREASES
Resistance
Amount of light
Resistance
Temperature
19/04/23
Wiring a plugWiring a plug
Earth wire
Neutral wire
Insulation
Live wire
Fuse
1.
2.
3.
4.
5.
6. Cable grip
The live wire of a plug alternates between positive and
negative potential relative to the Earth
The neutral wire of a plug stays at a potential close to zero
relative to the Earth
19/04/23DC and ACDC and AC
DC stands for “Direct Current” – the current only flows in one direction:
AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz)
1/50th s
230V
V
V
Time
T
19/04/23
Using an oscilloscopeUsing an oscilloscope
Q. What is the voltage and frequency of this supply?
This number tells you how many seconds each square on the horizontal axis
represents
This number tells you how many
volts each square on the vertical axis represents
19/04/23
FusesFuses
Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.
Words – large, harm, safety, melt, live, circuit, fuse
19/04/23
Power and fusesPower and fuses
Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by:
P
IVPower = voltage x current
in W in V in A
Using this equation we can work out the fuse rating for any appliance. For example, a 3kW (3000W) fire plugged into a 240V supply would need a current of _______ A, so a _______ amp fuse would be used (fuse values are usually 3, 5 or 13A).
19/04/23
Power and fusesPower and fuses
Copy and complete the following table:
Appliance Power rating (W)
Voltage (V) Current needed (A)
Fuse needed (3, 5
or 13A)
Toaster 960 240
Fire 2000 240
Hairdryer 300 240
Hoover 1000 240
Computer 100 240
Stereo 80 240
19/04/23
Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how much energy it uses every second.
In other words, 1 Watt = 1 Joule per second
E
TP
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)
19/04/23
Some example questionsSome example questions
1) What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds?
2) What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?
3) Farhun runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?
4) How much energy does a 150W light bulb transfer in a) one second, b) one minute?
5) Shaun’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a physics lesson?
6) Damien’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?
19/04/23
Earth wiresEarth wiresEarth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows.
Words – fuse, fault, metal, surges, touch
19/04/23
Charge (Q)Charge (Q)
As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation:
Q
TI
Charge = current x time
(in C) (in A) (in s)
19/04/23
Example questionsExample questions
Charge (C) Current (A) Time (s)
5 2
0.4 1
20 0.5
50 250
3 60
1) A circuit is switched on for 30s with a current of 3A. How much charge flowed?
2) During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for?
3) A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?
19/04/23
Energy and chargeEnergy and charge
The amount of energy that flows in a circuit will depend on the amount of charge carried by the electrons and the voltage pushing the charge around:
E
QV
Energy transferred = charge x voltage
(in J) (in C) (in V)
19/04/23
Example questionsExample questions
1) In a radio circuit a voltage of 6V is applied and a charge of 100C flows. How much energy has been transferred?
2) In this circuit the radio drew a current of 0.5A. How long was it on for?
3) A motor operates at 6V and draws a current of 3A. The motor is used for 5 minutes. Calculate: a) The motor’s resistance, b) the charge flowing through it, c) the energy supplied to it
4) A lamp is attached to a 12V circuit and a charge of 1200C flows through it. If the lamp is on for 10 minutes calculate a) the current, b) the resistance, c) the energy supplied to the bulb.
19/04/23
Random questionsRandom questions1) A battery has a voltage of 12V and it puts a current of
3A through a bulb. What is the bulb’s resistance?
2) Another bulb transfers 120C of charge in 2 minutes. What was the current through it?
3) A powerpack transfers 2,000J to a motor. If the motor ran on a voltage of 50V how much charge was transferred?
4) A hairdryer runs on a 50Hz power supply. If it has a power rating of 200W what fuse should it have?
5) An electric fire transfers 3MJ of energy. If it has a power rating of 2KW calculate how long it was on for, the current it ran on (assuming it was connected to the mains supply) and the amount of charge it transferred.
19/04/23
Structure of the atomStructure of the atom
A hundred years ago people thought that the atom looked like a “plum pudding” – a sphere of positive charge with negatively charged electrons spread through it…
I did an experiment (with my colleagues Geiger and Marsden)
that proved this idea was wrong. I called it the “Scattering
Experiment”
Ernest Rutherford, British scientist:
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The Rutherford Scattering ExperimentThe Rutherford Scattering Experiment
Alpha particles (positive
charge, part of helium
atom)
Thin gold foil
Most particles passed through, 1/8000 were
deflected by more than 900
Conclusion – atom is made up of a small, positively charged nucleus surrounded by
electrons orbiting in a “cloud”.
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The structure of the atomThe structure of the atom
ELECTRON – negative,
mass nearly nothing
PROTON – positive,
same mass as neutron
(“1”)
NEUTRON – neutral,
same mass as proton
(“1”)
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The structure of the atomThe structure of the atom
Particle Relative Mass Relative Charge
Proton 1 +1
Neutron 1 0
Electron 0 -1
MASS NUMBER = number of protons + number of neutrons
SYMBOL
PROTON NUMBER = number of protons (obviously)
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IsotopesIsotopesAn isotope is an atom with a different number of neutrons:
Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.
Notice that the mass number is different. How many neutrons does each isotope have?
A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.
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Background RadiationBackground Radiation
Radon gas
Food
Cosmic rays
Gamma rays
Medical
Nuclear power
13% are man-made
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Types of radiationTypes of radiation
1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom)
2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle.
3) Gamma – after or decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed.
Unstable nucleus
Unstable nucleus
Unstable nucleus
New nucleus
New nucleus
New nucleus
Alpha particle
Beta particle
Gamma radiation
Words – frequency, proton, energy, neutrons, helium, beta
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Nuclear fissionNuclear fission
Uranium or
plutonium nucleus
Unstable
nucleus New nuclei (e.g. barium
and krypton)
More neutron
s
Neutron
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Chain reactionsChain reactions
Each fission reaction releases neutrons that are used in further reactions.
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Nuclear Fusion in starsNuclear Fusion in starsProton Neutron
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