Physics Flashcards
What does a substance that loses electrons become
Positively charged
What happens if charges in an ion:
Are the same.
Opposite.
One is charged the other isn’t.
Repel
Attract
Attract
How can you tell if an insulator is charged
Two
It attracts small pieces of dust and paper
When a balloon is charged it sticks to a wall
Two problems with static
Dust and dirt are attracted to insulators such as computer screens
Clothes made from synthetic materials cling to each other and to the body
Two dangers of static
If there are flammable gases or a high concentration of oxigen a spark could ignite the gases and cause an explosion
If you touch something with an electric charge on it it gives you a shock and could cause a heart attack
Safety measures from static shocks
An object that might be charged is connected to the earth by a wire so any charge disapaits
In a factory workers stand on an insulator matt so charges can’t be earthed through them
Lorries containing flammable liquids and gases are connected to the earth through earth through earth wire befor being loaded
When an aircraft is fueled static can build up this can causes sparks which can ignite the fuel a wire is used to earth the aircraft before it is fueled
What are five examples of uses of static
Photocopiers and laser printers
Defibrillators
Electrostatic dust precipitators
Paint spraying powder coats
Insecticide sprays
What is an electrical currant
A flow of electrical charge
How does a conventional current flow
From the post stove side of the terminal to the negative side
In what direction do electrons move compared to the conventional current
The opposite way
How do electrical conductress differ to insulators
Their electrons can move from atom to atom
What is the unit of charge
The coulomb c
What is the uk mains supply’s voltage and frequency
230v
50hz
What happens to the current when the components are connected in series
The current is the same
What happens to the current of components connected in parallel
It is shared
What is the word used to describe the fact that the total current going into the split in a parallel circuit is the same as the one going out
The current is CONSERVED
What is the unit for current
Amperes
How must an ammeter be connected into a circuit
In series
What does a substance that gains electrons become
Positively charged
How must a voltmeter be connected to a circuit
In parallel
If two 1.5v cells are connected in series in opposite direction what is the voltage
0
If two 1.5v batteries are connected in series facing the same direction what is the voltage
3v
What is the relationship between energy transferred, potential difference and charge
Joules=voltage x coulombs (charge)
What is the unit for resistance
Ohms
What do resisters do in a circuit
Reduce the amount of current flowing
What is the name for a variable resistor
Rheostat
What happens to the current as you increase the potential difference
It increases
What is the equation for the relationship between resistance voltage and current
Resistance=voltage/current
R= v/a
What is the relationship between voltage current and resistance
Voltage=current x resistance
What is ohms law
The result that the current flowing through a resistor=the voltage across the resistor. Providing the temp stay the same
What does it mean if the current flowing through a resistor is directly proportional to the voltage across it
It follows ohms law
Does a filament lamp follow ohms law
No, the resistance increases as the current increases
What is the current potential difference graph for a diode
A straight line then a steep line going to the right
This is because diodes have a very high resistance one way so it can only flow the other way
What is a thermistor
Thermistors are temperature sensors their resistance decreases as the temperature increases
A use is in fire alarms
What is the symbol for a thermistor
A rectangle in the circuit with a line underneath it which then turns and goes through the box at a 45 degree angle
What are ldr’s
Light dependant resistors. Used in automatic security lights. Their resistance decreases as the light intensity increases
What is the symbol for an ldr (light dependant resistor)
A rectangle in the circuit with a circle around it. Stows point to it in accordance to where the light is coming from
What is the energy transfer I’m a resistor
Plus two uses
Some of the energy from the electrical current gets turned into heat
Heating water in an electric kettle
Electric fires
What causes the heat transfer in wires
The free flowing electrons colliding with ions in the lattice structure of the metal each collision causes heat to transfer to the lattice
What happens to a resistor as it’s temperature increases.
It’s resistance increases
What is diplacement
Distance traveled in a straight line
What is the velocity
The velocity of an object is its speed in one pert inculcate direction
What are the four vector quantities of a moving object
Displacement
Velocity
Acceleration
Force
How do you find the distance traveled on velocity time graphs
The area below the line
What are the two factors in the size of acceleration
The size of the resultant force
Doubling the resultant force doubles the acceleration
The mass
Doubling mass halves the acceleration
What is the strength of gravity on earth
Ten newtons per kilogram
The three stages of falling
Acceleration downwards of the object no air resistance
Resultant force is acting downwards
Object gains speed weight stays the same but air resistance increases
Resultant force is acting downwards
Weight is balanced with air resistance there is no resultant force reaches terminal velocity
How do seat belts prevent injury in a car crash
Stop you moving inside the car
Stretch slightly to reduce the time taken for the body to reach zero so reduces forces on it
How do airbags help you survive a car crash
Increase the time for the heads movement to reach zero to reduce forces on it
Act as a cushion to stop cuts
What two things the amount of work done depend on
The size of the force on the object
The distance the the object moves
What is the relationship between work done by brakes and the loss in kinetic energy
Work by brakes=loss in kinetic energy
What happens to the braking distance of a car if it’s speed doubles
It quadruples
What does power measure
How quickly work is being done
What is the measure of power
Watts
What does the amount of gravitational potential energy depend on
Mass
Height above ground
What are the gravitational field strengths of the earth moon and Jupiter
Earth 10n
Moon1.6n
Jupiter26n
What are the dependant values on the size of kinetic energy in a moving object
Speed and mass
What is the relationship between work done by brakes and the loss in kinetic energy
They are equal
What is an example of conservation of energy
Newtons pendulum
What makes a material radioactive
The nucleus of the atom is unstable and can decay by giving off radiation in the form of alpha particles beta particles or gamma rays
What is used to measure radioactivity
A Geiger counter
What is the activity of a radioactive material measured in
Becquerels
What is the activity of a radioactive material
The number of nuclei that decay and give off radiation every second
What is an alpha particle made of
Two protons and two neutrons, same as a helium nucleus
What is a beta particle made of
A fast moving electron
What is a gamma ray made of
High energy electromagnetic radiation
How well does gamma ionise
Weakly
How well do alpha particles ionise
Very well
How well do beta particles ionise
Medium
What happens after alpha decay
A new element is formed two places lower in the periodic table
What happens after beta decay
The nucleus has one more proton and one less neutron
Steps of fission 4
Neutron fired into nucleus
Neutron hits nucleus
Nucleus splits into smaller nuclei called daughter nuclei and releases two or three more neutrons
The released neutrons hit more uranium nuclei
Where is the most dangerous nuclear waste stored
Glass like blocks deep in the ground
How else can a nuclear reactor be used
Can make other nuclei radioactive because they absorb the neutrons which makes their nuclei unstable
These are used as tracers in hospitals
How do control rods reduce reaction speeds and what are they made of
When hit by a neutron the daughter nuclei make two or three extra neutrons, this reaction is a chain reaction and if not controlled would easily spiral out of control
Control rods are made of boron which absorbs the neutrons, this slows down the reaction as less neutrons are hitting new nuclei
The control rods are lowered to slow the reactiOn down and raised to speed it up
Two steps of fusion
Two hydrogen atom collide and fuse together
The hydrogens fuse to produce a helium atom and energy
What is the difficulty of nuclear fusion
Both hydrogen atoms are positively charged which causes electrostatic repulsion so it has to be very hot for the nuclei to coliseum as they then move faster
Pressure and heat have to be very high and are more expensive to produce than the energy made by fusion
Why was cold fusion never considered to work
Many attempts to reproduce the results failed
So it did not pass the peer review
How do rocks emit radiation
Radon gas emited
How is alpha radiation used
Smoke detectors
Americium releases alpha which ironises the air in a detector smoke from fire ionises differently and causes the alarm to go off
What are the uses of beta two
Medical tracers certain chemicals concentrate in damaged or diseased parts of the the body radiation detectors are placed around the body to build an image of the inside
Measuring thickness of materials
The thicker the material the more radiation is absorbed and the less radiation reaches the detector
The detector then sends signals to the machine to decrease the size of the material
Uses of gama
Treatment of cancer
Sterilising medical equipment no heat so plastics can be sterilised
What does the rate of nuclear decay depend on
The type of material
The number of un decayed nuclei present the greater the rate
How is carbon fourteen formed
Cosmic rays hitting he atmosphere
How is carbon dating done
Using the half life of carbon 14 we can judge the age of something as the amount of carbon 14 on earth always stays the same
How is the age of rocks found
The ratio of uranium to lead
As the rock gets older there is more lead available
What accounts for the most background radiation
Radon gas
Dangers of ironising radiation on the body
Breaks molecules into fragments
The ions then react with other molecules in cells
Charged particles can react with DNA which causes mutations and cancer
Five precautions around radioactivity
Using tongues to pick up sources
Surveys kept in lead containers
Sources never pointed at people
Protective clothing
Exposure times limited
Disadv to nuclear energy
Non renewable
If accident large amounts of radiation released
Nuclear waste stays radioactive for thousands of years
How is low level waste disposed
Put in drums and submerged in concrete
How is intermediate level waste disposed
Mixed with concrete then put in stainless steel drum
How is high level n waste stored
Stored under water in large pools for 20 years then put in underground store where air can circulate and cool it
