Question post test
What is an electrical field?
The region surrounding a charged object is called an Electrical Field.
Why does a compass point North on the Earth?
A compass points North on earth because the magnetic south pole is actually located at the geographic north pole. Opposites attract! So the north end of a compass needle lines up with the magnetic field lines of the Earth because the north end of the needle is attracted to the Earth's magnetic South Pole.
What is a magnetic domain and what types of materials contain magnetic domains?
A magnetic domain is a region in a magnetic material in which the magnetic fields of the atoms all point in the same direction.
What is the difference between an electric motor and an electric generator?
An electric motor changes electrical energy into mechanical energy. Almost every time a device uses electricity to make something move, there is a motor involved. In a motor, a coil of wire called an armature (an electromagnet when current runs through it) rotates as its poles are pushed or pulled by the poles of a magnet. Electromagnet Induction is when a magnetic field creates an electric current in a wire. Generators use electromagnetic induction. Generators change mechanical energy into electrical energy. This is the opposite of electric motors.
Is an electromagnet a permanent magnet or a temporary magnet? Why?
An electromagnet is a TEMPORARY magnet. Temporary magnets are made out of magnetic materials that have magnetic domains. When an electric current runs through a wire coil it generates a magnetic field. That magnetic field causes the magnetic domains of the electromagnets iron core to align so that all of the north poles are facing one direction and all of the south poles are facing the other direction. As soon as that electric current stops, the magnetic domains of the iron core no longer line up so it stops being a magnet.
How is an electromagnet created?
An electromagnet is created when a wire is coiled around an iron core (like a nail or screw) and then attached to a power source (like a battery). When electric current flows through the wire coil it generates a magnetic field. The magnetic field created by the wire magnetizes the iron core so that the core can be used as a magnet.
What is the relationship between the amount of electric charge on an object and the strength of the electric force exerted by the object?
As charge increases, the electric force exerted by objects increases.
What is the relationship between distance and the strength of an electric force?
As distance increases, the electric force exerted by objects decreases.
How does distance affect the gravitational force of an object?
As the distance between two objects INCREASES, the gravitational force between them DECREASES.
As a pendulum swings, energy is converted back and forth between potential and kinetic energy? Where is the potential energy greatest in the swing of a pendulum?
At the highest point of the pendulum, potential energy will be greatest.
What is the difference between a balanced force and an unbalanced force? Draw a force diagram of a tug-o-war game that illustrates balanced force. Do the same thing for unbalanced forces.
Balanced forces result in no change in motion of an object. If two forces are balanced, it means that they are of equal magnitude (or size) but acting in opposite directions. Unbalanced forces cause an object to accelerate (that means there will be either a change in the speed of the object or in the direction the object is traveling). If forces are unbalanced, it means that the magnitude of one force is greater than the magnitude of another force OR that the forces are not acting in exactly opposite directions. When unbalanced forces are acting on an object the NET FORCE is greater than zero. When balanced forces are acting on an object, the NET FORCE is equal to zero.
How can you increase elastic potential energy?
Change the amount of compression or tension force applied to the object so that the object wants to return to its original position.
What is the difference between a contact force and a non-contact force?
Contact Force- a push or pull on an object by another that is touching it. Non-contact Force- a force that one object can apply to another without touching it.
Where is chemical potential energy stored?
Energy is stored in the chemical bonds between atoms.
There are three types of friction that we discussed on class: Static, kinetic and fluid. Describe each type of friction.
Friction is a contact force that is causes by two objects moving past one another. Friction always opposes motion. Static Friction - A force that opposes the motion of an object that is at rest. Static friction must be overcome in order for an object to move. Kinetic Friction - A force that opposes the motion of an object that is in motion. If an object is moving across a surface there is a frictional force between the object and the surface it is moving across. For example, in the bike example below (#7), there is friction between the tires of the bike and the road. Fluid Friction - Also called "drag", fluid friction is a force that opposes the motion of an object as it moves through a fluid. Fluids are gases and liquids. Fluids are made of particles of matter. Objects moving through these particles experience friction with the particles. Air resistance is a specific type of fluid friction that occurs when an object moves through air (like when a sky diver falls towards the surface of Earth through air).
What are the three types of non-contact forces discussed in class.
Gravitational Forces- Gravitational fields exist around objects with mass. If a second object with mass is placed in the field, the two objects experience attractive gravitational forces toward each other. Every object exerts a gravitational force on every other object with mass. Magnetic Forces- A force of attraction or repulsion between the poles of two magnets OR a push or a pull a magnetic field applies to a magnetic material. Electrical Forces- The region surrounding a charged object is called an Electrical Field. An electric field applies a force, called an electric force, to other charged objects within the first object's field, even if the objects are not touching. The electric force applied by the object's electric field will either attract or repel other charged objects.
What two forces are acting on a skydiver as they fall towards the surface of earth after jumping out of an airplane?
Gravity - Gravitational force is directed toward the center of Earth, so a sky diver falls down towards the surface of Earth Air Resistance (or Fluid Friction) - Air resistance is a force that OPPOSES gravity. That means while gravity is pushing a sky diver down towards the surface or Earth, air resistance is actually acting to push the sky diver up in the opposite direction of gravity.
In which direction does gravity act on Earth?
Gravity on Earth is a center-directed force. From the surface of Earth, gravity points downward toward the middle of earth.
High or low-A positive charge in close proximity to another positive charge
High potential energy because the charges want to move away from each other.
High or low-A positive charge that is far away from a negative charge
High potential energy because the charges want to move towards each other.
High or low- A positive charge placed near a negative
Low potential energy because the charges are already attracted to each other and there will not be any movement of charges.
How can you increase the gravitational PE of an object with a given mass?
If the mass stays the same, increase the height of the object to increase gravitational PE.
How could you turn an electromagnet off?
In order for an electromagnet to work, an electric current has to be passing through a wire coil around an iron core. You can turn the electromagnet off by stopping the electric current from flowing through the wire coil. In the electromagnets we made during class, you would simply have to disconnect the wires from the battery in order to turn off the electromagnet. Removing an electromagnet from its power source essentially turns off the electromagnet.
How is electrical energy produced in power plants?
In power plants, mechanical energy (from sources like steam, blowing wind, falling water, and ocean tides) is used to rotate turbines. Turbines are machines that have blades that are caused to spin by pressure from water, steam, or air. The turbines turn magnets inside coils of wire, which generates electricity (using electric generators).
Where is elastic potential energy stored?
In springs or rubber bands-- objects that can be pushed or pulled by compression and tension forces, respectively.
You are riding your bike down a flat, straight road. After a few minutes you stop pedaling. Eventually you come to a stop. How does this scenario relate to inertia? What causes the bike to come to a stop?
Inertia is the tendency of an object to resist changes in motion. When you are riding your bike and you stop pedaling you continue to move forward because the bike has inertia. After you stop pedaling you are no longer applying a force to the bike, but it continues to move. Objects in motion DO NOT require a sustained force in order to continue moving. Newton's first law of motion tells us that an object in motion will stay in motion unless an outside force acts on it. In this case, the outside force that causes your bike to come to a stop is friction between the tires of the bike and the road. Friction slows your bike down!
Where is the magnetic field the strongest around a magnet?
Magnetic Poles are the place on a magnet where the force it applies is the strongest because the force lines are closer together.
How can you increase the strength of a magnetic force?
Magnetic force (attraction or repulsion) becomes stronger as magnets move closer together. Magnetic forces become weaker as magnets move farther apart.
Give three examples of objects that are capable of storing elastic potential energy.
Marshmallow Launcher, Wind-up Toy, Sling Shot, Mattress Springs, Bouncy Balls, Rubber Bands, Slinky, Clothespin, Music Box, ect.
What are the two factors that affect gravitational potential energy? Explain the relationship between each factor and gravitational PE.
Mass- as mass of the object increases, gravitational PE increases. Height- as an object's height above the reference point increases, gravitational PE increases.
Relate Newton's first law of motion to what happens when someone slams on the break of a car moving at sixty miles per hour. (Assume you are a passenger in the car with a seat belt securely fastened.)
Newton's first law of motion states that an object at rest remains at rest unless an outside force acts on the object, OR an object in motion will maintain that same motion unless an outside force acts on the object. If someone slams on the breaks of a car you are riding in your body continues to move forward even though the car slows down because your body has inertia (or a tendency of an object to resist changes in motion). Your body is eventually stopped by the seatbelt you are wearing. The seatbelt applies a force in the opposite direction of the movement of your body. Newton's first law of motion tells us that your body will continue its forward motion unless it is stopped by an outside force. In this case, the outside force that changes your motion is the force of the seatbelt!
What unit do scientists measure force in?
Newtons (N) are the unit of force.
At an atomic level, what is the difference between non-magnetic materials, magnetic materials, and magnets? Draw a picture to represent the atomic view of each type of material.
Non-magnetic Materials- the magnetic fields of the atoms point in different directions. As the fields around the atoms combine, they cancel each other out. (Figure A) Magnetic Materials- a magnetic material is any material that is strongly attracted to a magnet. In magnetic materials, atoms form groups called magnetic domains. A magnetic domain is a region in a magnetic material in which the magnetic fields of the atoms all point in the same direction. The magnetic domains all point in different directions, so the magnetic fields cancel each other out. This results in the object having no effective magnetic field. (Figure B) Magnets- an object is considered a magnet with a magnetic field when all of the domains align. When domains are lined- up, a single magnetic field exists around the entire object. (Figure C)
What does the phrase "opposites attract" mean in terms of electrical potential energy?
Oppositely charged particles attract each other; similarly charged particles repel one another. The positively charged proton attracts the negatively charged electron. Electrons can move from one atom to another. A change in the position of charged particles relative to each other is evidence of a change in electrical potential energy.
What are the charges of the three sub-atomic particles (protons, electrons, and neutrons)?
Protons- Positive (located in the nucleus of the atom) Electrons- Negative (located in the electron cloud outside of the nucleus) Neutrons- Neutral/No Charge (located in the nucleus of the atom)
What gives evidence that the chemical potential energy of a substance has changed?
Rearranging atoms into new positions to form new substances (chemical reaction) is evidence that the chemical potential energy has most likely changed. There is a formation of gas which can be seen by a fizzing or bubbling The reaction will cause heat, light or odor to be emitted A color change is produced A solid is formed during the change
If an electron is put inside the electrical field of an electron, what will happen two the two particles?
The electric force applied by the negatively charged electron will repel the other negatively charged electron.
If a proton is put inside the electrical field of an electron, what will happen two the two particles?
The electric force applied by the positively charged proton will attract the negatively charged electron.
What two factors affect the strength of an electrical field?
The force of attraction or repulsion between two charged objects depends on two things: a. The amount of charge the two objects have b. The distance between the two objects
What are the two factors that affect gravitational force? (HINT: Do NOT get gravitational FORCE confused with gravitational POTENTIAL ENERGY! They are different things! One is a force the other is a type of energy.)
The magnitude (or size) of gravitational force is dependent on the mass of two objects and the distance between those two objects.
How does the mass of an object affect the gravitational force of an object?
The more massive an object is, the greater the gravitational force it exerts on other objects. This is why we can feel the earth's gravitational force! The Earth is MASSIVE! And, as such, its gravitational force is great. Any two objects that have mass exert a gravitational force on one another. But because most objects don't have a significant mass, the attractive force of gravity between them is too weak to influence the motion of the objects.
What factors affect the strength of an electromagnet?
Two factors affect the strength of an electromagnet: the number of coil loops around the iron core (the nail or screw) and the amount of electric current flowing through the wire coil. More coils loops create a stronger magnetic field; more electric current (like a stronger/ bigger battery) creates a stronger magnetic field.
When a magnetic material is placed in the magnetic field of a magnet, what happens to the domains of the magnetic material?
When a magnetic material is placed in the magnetic field of a magnet, it causes all of the domains of the magnetic material to align along the field lines of the magnet. If a force is causing the domains of a magnetic material to align, the material then becomes a magnet.
Electrons can move from one atom to another atom or even from one object to another object. If an object LOSES electrons, does it become NEGATIVELY charged or POSITIVELY charged?
When an atom loses an electron, it becomes positively charged. When an atom gains an electron, it becomes negatively charged.
When is chemical potential energy released?
When the bonds are broken during a chemical reaction in order to create a new substance.
When you are sitting still in the classroom answering this question, is your body in motion?
YES! Your body is in motion because the Earth is rotating around its axis. The Earth is also orbiting the Sun and the Sun is orbiting the Milky Way galaxy. The Milky Way galaxy is moving through the universe. OR NO! Your body is NOT in motion if your frame of reference is the school building in which you are sitting. Describing motion is all about perspective. When you describe motion you have to choose a frame of reference, or a point of view, from which to describe the motion of an object.
