Tagged: physics
How to make an electromagnet
Aim: How to make your own electromagnet.
Prelab discussion:
1. What do you need to make an electromagnet?
An electromagnet starts with a battery (or some other source of power) and a wire.
2. What does a battery produce?
What a battery produces is electrons.
3. If you look at a battery, say at a normal D-cell from a flashlight, you can see that there are two ends. What is marked on the ends of the battery?
One marked plus (+) and the other marked minus (-).
4. Electrons collect at the negative end of the battery, and, if you let them, they will gladly flow to the positive end. How do you let electrons flow?
The way you “let them” flow is with a wire.
5. If you attach a wire directly between the positive and negative terminals of a D-cell, what are the three things that will happen?
a. Electrons will flow from the negative side of the battery to the positive side as fast as they can.
b. The battery will drain fairly quickly (in a matter of several minutes). For that reason, it is generally not a good idea to connect the two terminals of a battery to one another directly. Normally, you connect some kind of load in the middle of the wire so the electrons can do useful work. The load might be a motor, a light bulb, a radio or whatever.
c. A small magnetic field is generated in the wire.
Procedure:
1. Wrap your wire around a nail 10 times.
2. Connect the wire to a battery. You just made an electromagnet.
3. Bring one end of the nail near a compass
What do you observe? The nail behaves just like a barmagnet.
4. Place a set of metal paper clips on the table near the barmagnet. What happens? the paper clips are attracted to the electromagnet
5. Dissconect one of the ends of the wire. What happens?_______________
6. Reconnect the wire. What happens?
7. Dissconnect the wire and increase the turns of wire from 10 to 100.
8. Place the staples near the electromagnet. What do you observe?
Magnetism Experiments
Magnetism Experiments:*howstuffworks.com
1. What is the magnetic power of a single coil wrapped around a nail? Of 10 turns of wire? Of 100 turns? Experiment with different numbers of turns and see what happens. One way to measure and compare a magnet’s “strength” is to see how many staples it can pick up.
2. What difference does voltage make in the strength of an electromagnet? If you hook two batteries in series to get 3 volts, what does that do to the strength of the magnet? (Please do not try any more than 6 volts, and please do not use anything other than flashlight batteries. Please do not try house current coming from the wall in your house, as it can kill you. Please do not try a car battery, as its current can kill you as well.)
3. What is the difference between an iron and an aluminum core for the magnet? For example, roll up some aluminum foil tightly and use it as the core for your magnet in place of the nail. What happens? What if you use a plastic core, like a pen?
4. What about solenoids? A solenoid is another form of electromagnet. It is an electromagnetic tube generally used to move a piece of metal linearly. Find a drinking straw or an old pen (remove the ink tube). Also find a small nail (or a straightened paperclip) that will slide inside the tube easily. Wrap 100 turns of wire around the tube. Place the nail or paperclip at one end of the coil and then connect the coil to the battery. Notice how the nail moves? Solenoids are used in all sorts of places, especially locks. If your car has power locks, they may operate using a solenoid. Another common thing to do with a solenoid is to replace the nail with a thin, cylindrical permanent magnet. Then you can move the magnet in and out by changing the direction of the magnetic field in the solenoid. (Please be careful if you try placing a magnet in your solenoid, as the magnet can shoot out.)
5. How do I know there’s really a magnetic field? You can look at a wire’s magnetic field using iron filings. Buy some iron filings, or find your own iron filings by running a magnet through playground or beach sand. Put a light dusting of filings on a sheet of paper and place the paper over a magnet. Tap the paper lightly and the filings will align with the magnetic field, letting you see its shape!
Introduction to Static Electricity*
| Essential Questions/ Major Concepts : | Attraction and repulsion of like and unlike charges Three methods of charging objects (conduction, friction, induction) |
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| Instructional Strategies/ |
Charge balloon and pith balls(video) | |
| Resources/ Curriculum Materials : | Chapter 7, Sec.#1, pgs 192-199 Study guide and reinforcement worksheet p23 Interactive Chalkboard CD-ROM p190 (Text) |
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| Writing Journal: | Students write essays that will: • Discuss the effects of positive and negative charges • Discuss attraction and repulsion • Distinguish between the three methods of charging Section review questions p199 |
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| Key Vocabulary : | Static, conductor, insulator, law of conservation of charge, induction, conduction, friction |
Exploring Different Forms of Energy
Aim: How to connect real world examples of different Forms of Energy to mathematical formulas.
Unitedstreaming.com “elements of physics: energy work and power”
This video demonstrates how the formula W = Fx is a definition of energy, explains kinetic energy and givesI a number of examples. This is a great review because it also ties in potential energy and gives a number of examples. It illustrates and explains some of the types of energy such as electromagnetism, nuclear energy, chemical energy, sound energy, and heat energy. Students will see real life examples of energy exchanges and see how the three laws of thermodynamics apply to real world scenarios. This video also discusses why Einstein’s formula E = mc 2 explains how matter and energy are different aspects of the same thing.This is a great overall review that ties the energy concept together.
Video Quiz follows.
Review for Test(unit study guide)
Notes
1. Distinguish between electrical, chemical, radiant, and thermal energy. What do they all have in common?
a)Electrical – energy associated with the movement of charged particles
b)Chemical – energy stored in chemical bonds
c)Radiant – energy carried by electromagnetic waves
d)Thermal – kinetic & potential energy of the particles in an object
e) All of these forms of energy have the ability to do work.
2. What is kinetic energy? What is potential energy? Describe how a swinging pendulum demonstrates the back-and-forth conversion of potential energy to kinetic energy.
Kinetic energy is energy associated with moving objects, no matter how big or how small. Potential energy is energy stored in an object due to is position and location.
A swinging pendulum demonstrates both kinetic energy and potential energy. When a swinging pendulum is at the highest point in its swing, it has maximal potential energy and a minimal kinetic energy. At the bottom or lowest point in its swing, it has maximal kinetic energy and minimal potential energy.
3. Describe and give an example of the following types of potential energy…
a) elastic potential energy – energy stored when an object is compressed or stretched, such as a stretched rubber band
b) chemical potential energy – energy stored in chemical bonds which can be released by a chemical reaction, such as the energy stored in a typical household battery
c) electrical potential energy – energy due to the position of an electrical charge relative to other electrical charges, such as static electricity
d) nuclear potential energy –energy stored in the nuclei of atoms and released during nuclear reactions; the energy produced at nuclear power plants are an example
4. Calculate the gravitational potential energy of a 500-kg rock resting on the edge of a 200-meter cliff.
Gravitational potential energy = mass x gravity x height
GPE = 500 kg x 9.8 m/s2 x 200 meters
GPE = 980,000 Joule
5. Calculate the kinetic energy the rock mentioned in question 4 will have just before it hits the ground if it is moving at 10 meters per second.
Kinetic energy = ½( m x v2)
KE = ½ x [500 kg x (10 m/s)2]
KE = 2500 Joules
Homework:
Review for Test
Relating Work to Power
Aim:
How work, energy, and power are interelated.
How to use formulas to solve problems related to work, energy, and power.
1. State the law of conservation of energy. Why does a swinging pendulum eventually come to rest if this law is true? (ie, where does the energy go?)
The law of conservation of energy states that energy can be neither created nor destroyed. A pendulum will eventually slow and stop because of the downward pull of gravity and air resistance. The energy lost by the pendulum, however, is gained by the air molecules that are displaced by the pendulum.
2. Describe the two conditions necessary for work to be done on an object.
Work is done when a force is applied to an object and that object moves in the same direction as the applied force
3. What is the relationship between work and energy?
Work and energy are related in that there is a transfer of energy from the object applying a force to the object that moves as a result of that force.
4. A 1000-newton force is applied to a stalled car, causing it to move 8 meters. How much work is done on the car?
Work = force x distance
W = 1000 N x 8 m
W = 8000 Joules
5. Two students, each weighing 500 newtons, must travel 700 meters to get from the parking lot to their first period class. Student A walks and gets to his destination in 200 seconds. Student B runs and gets there in 100 seconds.
a. Which student does more work? Support your answer with calculations
Both students do the same amount of work because their mass is the same and their distance to class is the same…
Work = force x distance
W = 500 N x 700 meters
W = 350,000 Joules
b. Which student has more power? Support your answer with calculations.
Student B has more power because they did the same amount of work in half the time as student A.
Student A Student B
Power = work/time Power = work/time
P = 350,000 J/100 seconds P = 350,000 J/200 seconds
P = 35,000 watts P = 17,000 watts
Homeworkp 835 #40-55
Lab: measuring the effects of air resistance
Title: Measuring the effects of air resistance
Goals: measure the effect of air resistance on sheets of paper with different shapes.
design and create a shape from a piece of paper that maximizes air resistance.
Materials:
paper( 4sheets), scissors,meterstickstopwatchmasking tape
Procedure:
1. Copy the data table in your lab section. ( paper type, flatpaper,loosely crumpled paper, tightly crumpled paper, Your paper design also add a column for time. 2 columns.
2. Measure a height of 2.5 m on the wall and mark the height with a piece of masking tape.
3. have one group member drop the flat sheet of paper from the 2.5 m mark. Use the stopwatch to tome how long it takes for the paper to reach the ground. Record your time in your data table.
4. Crumple a sheet of paper into a loose ball and repeat step 3.
5. Crumple a sheet of paper into a tight ball and repeat step 3.
6. Use scissors to shape a piece of paper so that it will fall slowly. You may cut, tear , or fold your paper into any design you choose.
Summary
conclude and apply
1. Compare the falling times of the different sheets of paper.
2. Explain why the different-shaped papers fell at different speeds
3. Explain how your design caused the force of air resistance on the paper to be greater than the air resistance on the other paper shapes.
Homework page 82 #1-3
Atoms emit light
Do Now: Identify group and period properties of the periodic table.
Write the electron configuration of O, C, N, P, H, He, Ba, Li, Ne, Na, B, using the periodic table.
Aim: How to Calculate wavelength, frequency, and energy of electron emissions.
materials needed: reference tables – bohr model
Notes:
Using spectroscopy to analyze electron arrangement.
What energy level transition is indicated when the light emitted by a hydrogen atom has a wavelength of 103 nm?
n=3 to n=1
Which color of light would a hydrogen atom emit when an electron changes from the n=5 level to the n=2 level?
blue
Electrons release energy as they return to the ground state( excited to ground: high to low)
What is the formula that relates frequency with wavelength,lamda?
According to the visble light spectrum(reference table), which color light has the highest frequency.
Which has the highest wavelength?
Calculating energy changes within the atom.
Describe the relationship between ground state, excited state, and photons.
Describe Bohr’s model and compare it to quantum theory.
All moving particles, ie. electrons and light have wave-particle duality. Explain.
Activity OR Emission Spectra LAB handout
Define ground state
Define excited state
Draw and Analyze the Bohr model of the atom.
Draw and Describe the main parts of the electromagnetic spectrum(colored pencils) and give an example of each.
Describe the electron location of an electron in terms of probability.
Which configurations represent excited atoms
1s12s1
1s22s22p63s23p64s23d10
Practice Questions:
1) Which electron configuration represents an atom in the excited state?
A) 2-7 B) 2-8-2 C) 2-7-1 D) 2-8-1
2) What is the total number of electrons in the second principal energy level of a calcium
atom in the ground state?
A) 8 B) 6 C) 2 D) 18
3) If the principal quantum number n = 4, what is the maximum number of electrons that
can be found?
A) 18 B) 8 C) 32 D) 6
4) The maximum number of electrons that a single orbital of 3d could hold is
A) 3 B) 2 C) 10 D) 6
5) What is the frequency of an X ray that has a wavelength of 1.15 x 10-1 m?
A) 5.32 x 109 sec-1 B) 2.61 x 109 sec-1 C) 3.44 x 109 sec-1
D) 7.8 x 107 sec-1
6) As an electron moves from its ground state to its excited state, the potential energy of
the electron :
A) remains the same B) decreases C) increases
7) The characteristic bright line spectrum is produced when the electron:
A) moves to a higher level B) is lost by an atom
C) forms an ionic bond D) moves to a lower level.
8) The greatest energy absorption occurs when the electron moves from:
A) 1s to 3s B) 3p to 3s C) 4d to 4s D) 4s to 3p
9) The relationship between the frequency and the wavelength is:
A) direct B) linear C) equal D) inverse
10) What is the probability of finding an electron outside of its orbital?
A) zero B) 5% C) 10 % D) 95%
Homework
p70-74 and 116-149, 154-207
Difference between mass and weight
AIM: Difference Between Mass and Weight
(Students of physics often confuse mass and weight of an object and many also feel that there is no difference between the two, while the fact is that there is a lot of difference between the two.)
do now: what is mass?
Mass is the amount of matter present in a body and is an intrinsic property of the body. Mass of an object remains the same always at any place.
Weight on the other hand is the force which a given mass feels due to the gravity at its place. Weight is measured in units of Force like Newton (which is the SI unit of Force).
If your mass is 60 kgs then your weight is approximately 60 x 10 = 600 Newtons. This is because
Force = mass x acceleration (From Newton’s second Law)
Thus, weight = mass x acceleration due to gravity
If you go to moon your mass remains same, i.e 60 kgs, but your weight becomes less by 1/6 amount, since moon’s gravity is 1/6 that of earth.
Mass of a body is measured by balancing it equally with another known amount of mass. You keep known amount of masses like blocks of 1 kg, 2 kg etc on one side till both the sides balance and then add up the numbers on the known side of mass and thus calculate the unknown mass. This works because, when the masses are equal on both the sides of the balance the effect of gravity cancels out for both (i.e weight cancels out) and hence we can calculate the mass on one side of the balance if we know the mass on the other side of the balance.
Weight is measured using a scale which effectively measures the pull on the mass exerted by the gravity of the earth.
Student Acitivity: students will do white- boarding/ or poster boarding. They discuss and research differences, then summarize and organize it into a table.
Differences between Mass and Weight
Mass Weight
1. Is always a constant at any place and time Depends on gravity at the place
2. Is measured in kilograms in SI unit Is measured in Newtons (not in kilograms as one might think)
3. Is measured using balance Is measured using scales
4. Can never be zero Can also be zero
5. Is an intrinsic property of a body
6. Is independent of any external factor
Weight depends on mass of the object which is attracting it
Weight depends on force with which it is being attracted (which in turn depends on the distance between the two)
Teacher Demo:
Drop book, pencil together. Drop folder, ball together, or other object. (If an object is in freefall towards the attractor (like earth), even then it has weight, but it experiences weightlessness (like an astronaut in a spaceship around the earth) since it is obeying the force. Weight can be felt only when the body in question tends to oppose the force of gravity (like u and me sitting on the surface of the earth)
Remember that even though we are at rest due to the friction between our self and earth’s surface, our acceleration is not zero, it is still 9.8 m/s2 as the earth is constantly pulling us down towards its center. But we are resisting that pull and feel the force as weight.
Summary: Student presentation of posters/transparancy.
Homework:
workbook p101-104 # 1-16
Instantaneous Velocity
Aim: How do describe instantaneous Velocity.
Motivation: Demo: car in motion, have student time it with a stop watch, have student measure postition.
Materials needed: graph paper, transparancy (optional), meterstick, stopwatch
DO NOW: Student Activity: #1 Plot the following data on graph paper.
Time (seconds) Position(cm)
1 20
2 40
3 60
4 80
5 100
6 120
7 140
time should be on the x axis
After plotting the points, take the slope of the line(take 2 points on the line, find the change in the y direction and the change in the x direction). slope = change in y divided by change in x.
Speed and Velocity
is very, very small.
| |||||||||||||||||||||
Graphical Analysis of Velocity and Acceleration
Do Now: Draw a sketch of a distance time graph that shows speed and
also draw another sketch showing an object standing still. Draw a
velocity time graph of acceleration.
Motivation: Show free
falling object. Drop ball and book at the same time. Ask students what
hit the ground first? Or did they both hit at the same time? Relate
slope of a Distance vs. Time graph to velocity.
Aim: How to Describe possible ways an object can accelerate.
notes: graphical analysis is used to interpret velocity and uniform acceleration.
Calculate acceleration using a=(vf-vi)/deltat
a=deltav/deltat
Relate slope of a Velocity vs Time graph to acceleration.
The acceleration due to gravity(g) is 9.8 m/s2
Materials: Textbooks, tape, toy cars, meter stick or ruler, ball
Possible
Activity: Students are required to make a table of at least 5 distances
and 5 time data points. Devise an experiment that shows the
relationship. Using stopwatch, object, cars,etc
Possible
Activity: problem solving textbook/handouts. Decide which symbols
relate to each question. Create a chart that includes words, variable,
unknown, formula, plugin and final answer.
Notes on Stars and Galaxies
I. Stars & Their Characteristics
A. People often notice groups of stars that seem to form patterns in the night sky. These patterns are called constellations.i.e. The Big Dipper (Ursa Major), The Little Dipper (Ursa minor), Cassiopeia, Orion
B. The constellations rotate about a fixed point in the Northern Hemisphere as the Earth rotates on its axis. This is Polaris (The North Star).
C. The constellations change as the seasons progress because the Earth is in a different part of its orbit around the Sun.
D. Distances to stars are immense! The distance to the nearest star, our Sun, is considered 1 Astronomical Unit (1 AU). (93 million miles)
1. The distance light travels in 1 year is considered 1 light year.
- light travels 300,000,000 meters/second!
- 1 light year = 95,000,000,000,000 kilometers!
- The next nearest star, Alpha Centauri, is 4.3 light years
away!
E. Properties of Stars:
1. The Sun
- Diameter = 1,380,00 km
- Mass = 300,000 times earth’s mass
- Density = 1.4 g/cm3
2. Stars can be smaller than Earth or 2000 times as large as
our Sun!
3. Colors of stars are indicative of their temperatures.
Red = cooler stars
Yellow = medium temp
Blue/White = very hot stars
4. Stars are made mostly of hydrogen & helium
F. The brightness of stars is measured by astronomers as well.
1. Apparent magnitude refers to how bright the star appears
to us on Earth.
Bright stars = 1st magnitude
Dimmer stars = 6th magnitude
2. Luminosity refers to the actual brightness of a star. It is
also called absolute magnitude.
II. Kinds of Stars
A. Red giants are HUGE stars that are cooler and redder in color.
B. Super-bright red giants are called supergiants. These are the
largest of all stars and are very short-lived.
C. Dwarf stars are as large as the Earth, but are very dense. They
are 100,000 times as dense as earth!
D. Variable Stars vary in brightness over regular intervals. Cepheid
Variables pulsate over 1-50 day intervals.
E. Pulsars give off POWERFUL bursts of radio waves once a second.
Astronomers feel this is the core of a star that blew up.
III. Life Cycles of Stars
A. Stars form from huge clouds of gas and dust in space called
nebulae.
1. The gravity of the matter in this cloud causes the particles
to condense into a large sphere of matter.
2. Friction and pressure heats up the matter in the cloud. and
it begins to glow as a protostar.
3. When 1,000,000,000°C is reached, nuclear fusion takes
place and the star “ignites.”
Nuclear fusion – 2 hydrogen atoms smack together hard
enough to stick together and form a
helium atom. this gives off A LOT of
energy!
4. When the force of gravity is in balance with the force of
the exploding hydrogen, the star is said to be in the stable
state.
5. When the hydrogen in the core is used up, (this takes billions
of years to do) the star becomes unstable and expands and
cools to form a huge red giant.
6. As even more of the core is used up, it can no longer support
the heavy outer layers and collapses to form a white dwarf.
- These are the size of the earth
- Eventually fade and die
- Large white dwarfs can flare up brilliantly and explode
as a supernova. These can outshine entire galaxies!
7. The stuff left over after a supernova is called a neutron
star.
- Atoms’ electrons are crushed into their nuclei
- 10 km dia. and trillions of times more dense than the
sun! Most dense objects in the universe
8. As neutron stars collapse further onto themselves, their
gravity becomes so great that not even light can escape it.
It now becomes a black hole.
IV. Galaxies & The Universe
A. Galaxies are systems of stars containing billions of stars!
B. There are billions of galaxies in the universe!
C. The nearest 17 galaxies make up The Local Group.
D. Our galaxy is called the Milky Way. It is a spiral galaxy.
E. Types of galaxies:
1. Elliptical –
2. Irregular -
3. Spiral -
F. Origin of the universe – The Big Bang Theory
1. 15 billion years ago all matter in the universe was
concentrated into a mass the size of the sun.
2. This mass exploded to form all of the stuff we see in
the universe today.
3. Evidence -
a. Background radiation (an echo) of the explosion
still exists in deep space.
b. All galaxies seem to be moving apart.
