Unit 2: Electricity
Terms:
Static electricity: the build-up of electric charges on an object.
Electric charge: positive or negative particles that exert an electric force.
Electric forces: the attraction or repulsion between objects or particles that have an electric charge.
Electric discharge: the removal of an electric charge from an object. Example: shock, lightning
Current electricity: the continuous movement of charged particles (electrons) through a conductor.
Galvanometer: a device that is used to detect weak electric currents. It was named for Luigi Galvani.
Ammeter: a device used to detect strong electric current.
Ampere: the unit by which current electricity is measured. It is also the number of electrons moving past a point in a wire in one second.
Conductor: a material that allows electricity to flow through easily. Examples: water, steel, nails, and copper.
Battery: two or more cells joined together to produce an electric current.
Voltage: a measure of the amount of electrical energy supplied by each unit of electric charge by the electrons.
Volt: the unit that measures the electrical energy.
Voltmeter: a device used to measure the electrical energy that the moving electrons have.
Resistor: a device with a certain resistance to the passage of electric charges; used in electronic devices.
Cell: a device that converts chemical energy into electrical energy.
generator: a device that produces electrical energy from mechanical energy, usually from kinetic energy of steam or running water.
permanent magnet: a piece of hard steel alloy (usually straight or U-shaped) that stays magnetized for a long time.
electromagnet: a coil of wire, usually with an iron core, that becomes magnetized when a current exists in it.
thermocouple: device consisting of a junction of two different metals: it produces an electric current when the junction is heated.
solar energy: radiant energy that reaches earth from the Sun.
photoelectric effect: an effect in which light, shining on metal, causes electrons to be emitted from the surface of the metal, producing an electric current.
piezoelectric effect: an electric current produced by sound, due to the changing pressure of sound waves on certain crystals.
electric circuit: an uninterrupted conducting path for an electric current.
Variable resistor: a device that can be used to control the amount of current in an electric circuit.
Solar cell: device, made of metal, that converts light (sun) energy into electrical energy. Examples: street lights, calculators, cars (solar powered), satellites
1. This is how an object gains a charge of static electricity:
All objects contain the same amount of protons and electrons and are considered to be electrically neutral. When 2 unlike objects are rubbed together, electrons are dislodged from an object and added to the other object. The object losing electrons has more protons than electrons and therefore is positively charged. The object gaining electrons will have more electrons than protons and will be negatively charged.
2. The three laws of electric charges are: (1) opposite charges attract each other. (2) Similar (like) charges repel each other. (3) Charged objects attract natural objects.
3. The two components of an electric cell are: (1) electrodes: usually two different metals (or carbon) that allow electrons to enter or leave. Examples: carbon rod and zinc strip, copper wire and paper clip.
Electrolytes: solution or paste that conducts electricity. Examples: juice on fruit/ vegetable, ammonium chloride
4. An electric cell produces a supply of electric charge by: The material in the cell, electrodes and electrolytes, interact with each other causing a chemical reaction to occur. The result is that some electrons move from electrode into the solution (electrolyte) onto the other electrode. The electrode with the fewer electrons is positively charge while the electrodes with more electrons is negatively charged.
5.how electrons move through a conducting path;
Beginning at the negative electrode of the cell, electrons repel each other, throughout he length of the conducting wire to the positive electrode. At the same time the positive electrode of the cell attracts the electrode. This creates a current. As the current flows, the chemicals in the cell keep taking electrons from the positive electrode and giving them to the negative electrode until the cell is used up.
6. resistance: a measure of how much a material resists the passage of electric charges.
The four factors that affect the resistance in a wire are: I) length of the wire: the longer the wire the more collision the electrons will have with the atoms of the wire. Therefore the more resistance.
II) Diameter of the wire: the thicker the wire the more space the electrons have to move through and therefore have less collisions. A thick wire will have less resistance then a thin wire.
III) Temperature: the hotter the wire the more quickly the electrons and atoms of the wire will be moving. Thin wire causes more collision and therefore more resistance.
IV) Type: different types of wires offer more or less resistance to the passage of electrons. Example: tungsten wire offers more resistance then copper wire.
7. Using a permanent magnet and wire to make a generator you must first coil the wire. Then move the magnet towards and into the coil of wire. This will create current electricity. If you move the magnet out of the coil of wire the current will flow through the wire as long as the magnet is moving.
Three ways you could increase the amount of current produced by the generator are:
a) more coils of wire b) use a stronger magnet c) move the magnet/coil faster
7. The four main parts of a circuit are: I) source: part of an electric circuit that change chemical energy into electrical energy. Example: cell or battery II) conductor: part of the circuit that allows electrons to travel in a path. Example: wire III) control: part of the circuit that stops and starts the flow of electrons. Example: switch IV) Load: part of the circuit that changes electrical energy into some other form (heat, light or kinetic) Example: light bulb or motor.
9.Differences between a parallel and series circuit:
Series |
Parallel |
Has one path to follow |
Have more then one path to follow |
Appliances share the same electrical pressure |
Appliances to not share same electrical pressure |
Loads work together |
Loads work at different times |
When one bulb is removed the others go off |
When one bulb is removed the others stay lit |
Lights dim when adding load |
Give off the same amount of light if adding load |
|
|
10. On other sheet.
11. Two factors that could change the amount of current produced by a solar cell are: -distance between the solar cell and the light source -number of solar cells -intensity or brightness of the source -metal in the solar cell
The factors that affect the current produced by the thermocouple are: -amount of heat -length of wire(# of coils) -size of wire -type of wire
12.a) Everything, except motor will go on.
b) Nothing will work c)everything will work
Unit 3:Heat Transfer
Temperature: a measure of the average energy of the particles that make up a substance.
Thermal energy: the total energy of the particles of a substance.
Heat: energy transferred from a hotter substance to a cooler one.
Heat conductor :a material that allows heat to transfer through it readily (metal, pot)
Heat insulator: a material that does not allow electrons to pass easily from one particle of the material to the next (rubber, plastic, wood.)
Thermal conductivity: a measure of the ability of a substance to conduct heat
Convection current: the circulating path of a fluid caused by the application of heat.
Thermals: the rising part of a convection current in the atmosphere.
Radiant energy: -energy transferred by means of radiator. Some examples of radiant energy are: sunlight, TV, microwaves, x-rays, cell phones, satellites, heat lamp
1.Two types of heat transfer are:
conduction: transfer of energy through a material.
Convection: the process of transferring heat by the circulating motion of particles.
Radiation: the transfer of energy in a wave-like form.
2.The three main parts of particle theory are;
a)all matter is made up of tiny particle b) the tiny particles are always moving
a) the more energy the particles gain, the faster they move.
The difference between a hot and cold object:
If something is cold it means that its particles are moving relatively slowly. When it is hot its particles are moving more quickly. In any substance the particles will be moving more quickly or more slowly; that is, some have more energy and some have less. The average energy of the particles in the cold object is less than the average energy of the particles when it is hot.
3.Some facts about the particles:
solids: particles are tightly packed together move by vibrating particles are in fixed positions (cant change places)
liquids: -particles are still relatively close together, but they move freely particles can change places
gases: particles are widely spaced can move freely or exchange places
4. Temperatures of the soup is higher then the temperature of the spoon so heat transfers. Metal, being a good conductor also allows for this heat transfer. The particles in the spoon are tightly packed together. When the spoon is heated, the particles gain energy and vibrate faster, colliding with each other. The action causes a chain reaction throughout the particles in the spoon. Energy is transferred from the warm end of the spoon to the other end.
5. Three applications for heat conduction are: -hot rocks -curling iron -crimper
magic bag
6. How a liquid or gas is heated using convection currents:
The particles of air near the heater gain energy, requiring more space in which to move and collide. They spread apart, with the result that the heated air becomes less dense than the cooler surrounding air. The warmer, less dense air rises and is replaced by the cooler, more dense air. The air thus begins to move in a circular path, in a convection current.
7.How a sea breeze is created:
The land warms up more quickly then the water. The air above the land warms up as well and becomes less dense then the cooler air above the lake. This cooler air forces the less dense air to rise, producing convection current, blowing from the water towards the land.
8.Tell difference between convection and conduction:
Look at answers/definitions:
9.Six examples of radiant energy are:
sunlight, microwaves, x-rats, telephones, satellites and heat lamps
10. The three properties of radiant energy are:
(a) Waves of radiant energy can travel in a vacuums
(b) The waves all travel at an extremely high speed.
(c) Radiant energy travels in a straight line.
11. The three ways that energy can interact with matter are:
reflection: occurs if the radiant energy striking an object cannot get past the particles at the surface. When most of the energy is reflected, there is little rise in the temperature of the object increases.
Absorption: occurs if the radiant energy penetrates part way into an object where it can cause the particles to gain energy. When the radiant energy is absorbed, it increases the average energy of the particles and therefore increases the temperature of the object.
Transmission: occurs if the radiant energy can penetrate and pass through an object without being absorbed by the particles. No temperature increase observed.
12. The best type of materials that make the best absorbers/ emitters are dark, dull, black clothing.
13. RSI Value: the resistance to heat transfer of a material of a specific thickness.
Gypsum= 0.035 RSI per cm
Plywood= 0.087 RSI per cm
Fibreglass= 0.24 RSI per cm
RSI x thickness in cm +RSI
cm |
RSI Gypsum ( 1.8 cm)= 0.063
RSI Plywood (2.4 cm)= 0.2088
RSI fiberglass insulation (20 cm)= 4.8
Total 5.0718
14. Greenhouse effect: a warming of the temperature of the air caused by the trapping of heat as in a greenhouse, where heat is trapped inside a glass structure: this effect also occurs in the Earths occurs in the Earths atmosphere, where carbon dioxide molecules trap heat.
The greenhouse gases and where they come from:
methane: bogs digestion of cows carbon monoxide; cars
carbon dioxide: factories, forest fires, cars CFCs: aerosol cans
Ways to minimize the greenhouse effect:
- car-pooling -pump sprays vs. aerosol cans solar power vs fuel -walk instead of drive -dont burn bogs or flood them -use public transit instead of individual cars
etc.