Year 10 Stage 5 Universe Star Formation

Star formation – What you need to know……

 

  1.  Gravitational force is responsible for producing stars from interstellar cloud of gas called nebulae
  2.   Gravitational  continues to cause clouds of gases  (hydrogen) to aggregate (come close together) . Hydrogen atoms gather due to gravity force and undergoes nuclear fusion to form helium) and  form protostar. This goes on to form our Sun is also a star.  Among all the stars, it’s the nearest to the Earth, and so it appears big from seen from the Earth
  3.   Planets are the celestial bodies that revolve around a star and do not have any heat and light of their own.
  4.   Planets are smaller than stars and reflect the light of the sun.
  5.   Earth, on which we live, is one of the planets which revolve around the Sun.
  6.   A star and the planets revolving around it form a planetary system, just like our Solar System.
  7.   A group of stars along with their planetary systems form a galaxy.
  8.   The galaxy in which we live is spiral in shape and is called the Milky Way.
  9.   It contains over 200 billion stars, including the Sun.
  10.   There are billions of galaxies in the universe.
  11.   Life cycle of stars: (how stars is born and their transformations).
  12.   Red giant: a star produced when the core of Sun-sized star ran out of hydrogen
  13. Supernova: a giant explosion that occurs when a star many times larger than our sun ran out of nuclear fuel.
  14. White dwarf: hot dense star that is the remains of a red star.
  15. Black hole: is a collapsed star (due to very strong gravitational force) that even light cannot escape from it.
  16. Main sequence: a group of star lying in the line of the Hertz sprung Diagram running from top left to bottom right
  17.  Blue supergiants stars are ten or more times more massive than the Sun.
  18. Black dwarf: cold dark remains of a white dwarf.  (see number 23 above)
  19. Neutron star: remnants of  supernova consisting of entirely neutrons

STAR CHART:

 

 

Year 12 Scientific Skills – Errors

WORKING SCIENTIFICALLY: ERRORS, Fair Test etc.

 

  1. Outlier/Anomalies     

These are values in a set of results which are judged not to be part of the variation caused by random uncertainty.

 

Question 1: Matthew records the current in a resistor for a certain voltage and takes repeat readings, some of which are shown below:

 

Resistance (Ω) current (A)
1 2 3 4 mean
20 0.25 0.28 0.47 0.26
30 0.16 0.17 0.15 0.16
  1. Highlight the anomaly/outlier  in the table.
  2. Correctly determine the mean for each row.

 

  1. Measurement error: The difference between a measured value and the true value.

 

Question 2:  Simon measures the mass of a mug as being 250 g, but its true value  is actually 260 g. The difference is a measurement error.

(True value is the value that would be obtained in an ideal measurement. An ideal measurement is one that would have no errors at all)

           Calculate the percentage error in Simon’s measurement.

 

  1. Uncertainty

The interval within which the true value can be expected to lie, with a given level of confidence or probability, e.g. “the temperature is 20°C ± 2°C, at a level of confidence of 95%.”

The symbol ± is called “plus or minus”, and in the example above means “plus or minus 2°C” – i.e. the temperature is most likely to be between 18°C and 22°C.

The “level of confidence” expresses how certain the scientists are of their claim that the temperature is in the range 18—22°C.

 

Question 3:(a)  State the mean and the uncertainty for the following data:

                   33, 36, 28, 37, 29, 27, 30, 31

              

Question 4: In conducting an experiment comparing the speed of sound to the air temperature, Amasha’s thermometer has units of 1 o C and you have found the air temperature to be 20 o C. Calculate

  1. The absolute uncertainty
  2. The percentage uncertainty.

 

  1. Random Errors

 

These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next.

Random errors are present when any measurement is made, and cannot be corrected. The effect of random errors can be reduced by making more measurements and calculating a new mean.

Random errors may be caused by human error, a faulty technique in taking the measurements, or by faulty equipment.

 

Question 5: Fawad and Andrew are both timing a very fast pendulum with a stopwatch. Andrew can’t count the swings accurately as it is just too fast to keep up – this introduces a random error in his readings as he may think he has counted 20 swings when in fact it was 21.

Fawad doesn’t use the stopwatch very well. Although he starts it fairly accurately, he panics when having to stop it and is either too early or late. This is a random human error.

 

Suggest how Fawad and Andrew can improve the reliability of their data. Explain your answer.

 

Question 6: Matthew records the current in a resistor for a certain voltage and takes repeat readings, some of which are shown below:

Resistance (Ω) current (A)
1 2 3 4 mean
20 0.25 0.28 0.47 0.26
30 0.16 0.17 0.15 0.16

 

  1. Explain how Matthew’s table shows a random error.
  2. Explain how to improve the accuracy of the data in Matthew’s experiment.

 

  1. Systematic errors

 

These cause readings to differ from the true value by a consistent amount each time a measurement is made.

Sources of systematic error can include the environment, methods of observation or instruments used.

Systematic errors cannot be dealt with by simple repeats. If a systematic error is suspected, the data collection should be repeated using a different technique or a different set of equipment, and the results compared.

e.g. A systematic error occurs when using a wrongly calibrated instrument.

E.g. Ashley’s pendulum timing experiment was made worse by the fact that she also began counting at ‘1’ not ‘0’. So all her times, in addition to random in her counting, were also short of one full swing each making her calculated times all smaller than the ‘true values’.

 

7 FAIR TEST

A fair test is one in which only the independent variable has been allowed to affect the dependent variable.

A fair test can usually be achieved by keeping all other variable constant.

 

 

Question 7

Swee Yong and Pavan are investigating how the electrical resistance of wires changes with length. Unfortunately both of them let the current get too high for shorter wires, which dramatically increases their temperature. Since temperature affects resistance (in addition to the length), it is not a fair test.

 

  1. Identify the independent and dependent variables in their investigation.
  2. Explain why their experiment is not a fair test.  
  3. What could they do to make it a fair test?

Year 12 Physics – Working Scientifically Part 1 Steps in Depth Studies

Steps in Depth Studies/Scientific Investigation

 

Steps What the step involved:
  1. Planning
  • Writing a Hypothesis (Questioning and Predicting)
  • Researching background information (literature review), which aids you to refine or evaluate your hypothesis/question (to ensure you wil 
  • Writing the Method for a valid scientific investigation (evaluate methods and secondary sources;list of equipment,  logical steps, consider ethical issues)
    2. Conducting the investigation   
  • Carrying out a valid scientific investigation (it could be an experiment or a scientific investigation using secondary data sources). In conducting an experiment, ensure it is done safely, appropriate measuring devices or appropriate technology is used.
  • Data collecting (in an experiment) may involve recording/readings from instruments, organising (tables with correct units). Data collection (using secondary sources) may involve recording or organising (tables with correct units.
3. Analysing and interpreting data
  • Analysing data involves searching for some trends or patterns.
  • Studying sets of data to see if they fit the mathematical formula.
  • Evaluating data to draw or justify the conclusion, test hypothesis (correct or incorrect), modifying the hypothesis,  recommending further testing or improving the method.
4. Communicating
  • Writing a scientific report, designing a poster, making a video/film presentation, delivering an oral presentation, making a  (may involve other forms to communicate scientific ideas).
  • In any one of the above, appropriate scientific principles/terminology/language should be used and effective visualisations/technologies to convey scientific ideas.   

 

Yr 11 Electricity and Magnetism – Part 1 Electrostatics Experiments- Answers

PART A: CHARGED BALLOON

Inquiry Question:  How is the static electricity made and how a charged balloon interacts with

pieces of paper, someone’s hair, a stream of water and what happens when it brought next to a wall.?

AIM: To investigate the interaction of a charged balloon with various objects (charged and uncharged

PART A (CHARGED BALLOON)

 

  1. Rub one of the balloons with the cloth. Observe what happens when you place the rubbed side of the balloon which is now charged, close to the pieces of paper, your friend’s hair, a thin stream of water and next to the wall.

Record your observations below.

 

Activity: Place rubbed balloon close to Observation
a.    to pieces of paper. Balloon attracts the pieces of paper.
b.    your friend’s hair, Balloon attracts hair and the hair repels each other.
c.    a thin stream of water. Thin stream of water attracts/bends towards balloon.
d.    Next to the wall. Balloon is attracted to the wall.

 

PART B (CHARGED EBONITE AND PERSPEX RODS)

  1. Rub the ebonite rod with the cloth (flannel). Observe what happens when you place the rubbed rod which is now charged, close to the paper and a thin stream of water.

Record your observations below.

Activity: Place rubbed ebonite close to Observation
a.    to pieces of paper. Balloon attracts the pieces of paper.
b.    your friend’s hair, Balloon attracts hair and the hair repels each other.
c.    a thin stream of water. Thin stream of water attracts/bends towards balloon.

 

 

  1. Rub the Perspex rod with the cloth (flannel). Observe what happens when you place the rubbed rod which is now charged, close to the paper and a thin stream of water.

Record your observations below.

 

Activity: Place rubbed Perspex close to Observation
a.    to pieces of paper. Balloon attracts the pieces of paper.
b.    your friend’s hair, Balloon attracts hair and the hair repels each other.
c.    a thin stream of water. Thin stream of water attracts/bends towards balloon.

 

 

  1. Stick one of the charged rods onto the watch glass with Blu Tack so that it rotates freely and observe what happens when other charged rods are brought close to but not touching the charged rod.

Record your observations below.

Same charged rods repels and opposite charged rods attracts

 

  1. Write a conclusion for your experiments:

 

Experiments have shown that

  • Like signed charges repel each other (Coulomb law of electrostatics)
  • Unlike signed charges attract each other (Coulomb law of electrostatics)
  • Charged object attracts an uncharged objects.
  • For an isolated system, the net charge of the system remains constant
  • Charge Conservation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

An electroscope is a very simple instrument that is used to detect the presence and magnitude of electric charge on a body such as static electricity. The type of electroscope detailed in this experiment is called a pith-ball electroscope. It was invented in 1754 by John Canton. The ball was originally made out of a spongy plant material called pith. Any lightweight nonconductive material, such as aluminum foil, can work as a pith ball. The pith ball is charged by touching it to a charged object. Since the ball is nonconductive and the electrons are not free to leave the atoms and move around the ball, when the charged ball is near a positively charged body, or source, the negatively charged electrons are attracted to it and the ball moves towards the source. Conversely, a negatively charged source will repel the electrons, and therefore the ball. Electroscopes can also be used to detect ionizing radiation. In this case, the radiation ionizes the air to be more positively or negatively charged depending on the type of radiation, and the ball will either be attracted or repelled by the source. This is how electroscopes can be used for detecting x-rays, cosmic rays, and radiation from radioactive material.

Year 11 Physics – Electricity and Electromagnetism- Static Electricity

RUBBING YOUR SHOES ON CARPET CAN “ZAP” YOU. WHY?

 STATIC ELECTRICITY

The ancient Greeks discovered that rubbing amber with fur or other objects, it could pick up things like feathers! They may have discovered electricity. Electricity comes from the Greek word elector, which means ‘beaming sun’. This name came about because amber had a rich yellow glow in the sunlight.

 Have you had any of these experiences?

  • You walk to the tap to have a drink. Zap~
  • You put a jacket over your nylon team jumper. Zap~
  • Here comes mum in the car, and you touch the car door handle. Zap~
  • Even at home the carpet can zap you~

 

Static electricity is made when materials rub together. The more they rub together, the more electricity is made. This means bigger sparks. When you rub or brush a rod with a cloth, you rub off electrons. Having too many electrons makes a negative charge, and having too few electrons makes a positive charge. A spark is formed when electrons jump from where there are too many electrons to where there are too few.

The study of static electricity forces is called electrostatics. An uncharged plastic rod has an equal number of positive and negative charges. The negative charges are called electrons. Because they are at the edge of the atoms, electrons are easy to rub off. When you rub or brush a rod with a cloth, you rub off electrons. Sometimes the electrons are rubbed off the rod onto the cloth. And sometimes the electrons are rubbed off the cloth onto the rod.

Static electricity occurs with many non-metal materials. There is an electric field around objects which have an electric charge.

Year 11 Physics – Electricity and Magnetism

Static Electricity – What you already know – from Middle school

attract Two objects moved towards each other due to a force. Two like charges attract.
battery Power source that provides energy in a circuit and it is made up of two or more cells.
Bulb An electrical component which transform electrical energy into light energy. Also called a globe or lamp.
cell One unit of energy source which uses chemical reactions to produce current.
circuit A path for the electric current to flow
closed circuit A complete path for the current to flow out of the positive terminal of the battery and back to the negative terminal of the battery.

 

Coulomb’s law Is used to explain the relationship between electrical force and the two charges.

Coulomb’s law states that the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects.

electrical conductor A material that allows electricity to flow through it, e.g. metals
electrical insulator A material which does not allow electricity to flow through it, e.g. plastic
electric permittivity Has a value of  is 8.854 x 10-12 A2 s4 kg-1 m-3.

Is the measure of a material’s ability to store an electric field

electromotive force Is the electrical intensity or “pressure”  of potential difference across terminals of the electrical energy source such as a battery. This potential difference can drive an electric current if an external circuit is attached to the terminals of the energy source.
electricity Energy that comes from the flow of charged particles.
ferromagnetic  Materials such as iron, cobalt and nickel that are more easily attracted to the poles of the magnet or can be used as to make electromagnet.
magnetic field Region or an area surrounding a magnet where a force acts on magnetic materials.
motor An electrical component which rotates when it is connected to a battery. It transforms electricity energy into kinetic energy.
non – ohmic A conductor which does not obey Ohm’s law, for example, the tungsten filament in the bulb.
Ohm’s law Is the relationship between voltage and current in an ohmic device. V = IR,    where V=potential difference, I= current and R = resistance of material.
ohmic conductor The wires used to join electrical components.
conductor A material that allow current to flow through it. E.g. metals
Electricity supplied for use in homes and businesses.
open circuit A break in a circuit.
parallel circuit A circuit in which electric current flows through more than one paths in a circuit.
repel A force that pushes an object away. Two like changes will repel
permanent magnet A magnet (usually made of steel) that possesses its own permanent magnetic field.
permeability A measure of the ability of a material to permeability to allow  magnetic field to form inside of a medium
potential difference The difference in electric potential between two points which will then cause the electrons to flow.
power source A source of electrical power, can be a battery or mains.
repel A force that pushes an object away. Two like changes will repel.
series circuit A simple circular path in which electric current flows only one way through each part.
solenoid A cylindrical coil of wire which when current passes through it produces a magnetic field.
static electricity The build-up of electrical charges on a surface, for example, by rubbing your shoes on a carpet.
switch A device which can control the flow of electricity.
symbol A symbol used to represent an electrical component.
terminals The parts of a battery that need to be connected in the circuit.
voltage The amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called the voltage.

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