Bill Nye Electricity
Read and Respond • Read pages 272 -273 ▫ Give definitions for all bolded terms ▫ Answer questions
Correct Electric Charges Static Electricity Negative Charge Positive Charge Law of electric charges
Warm-Up: Matching 1. Static Charge A. Excess of electrons 2. Negative Charge B. A charge that stays in place. 3. Positive Charge C. A deficiency of electrons 4. Law of Electric Charges D. Like repels and opposite attract.
Laws of Electric Charges • Two objects with like charges, whether positive or negative, always repel one another. • When a positively charged object is near a negatively charged object, they attract one another. • Law: “Like charges repel another, and unlike charges attract one another. ”
Types of Electricity • There are two types of electricity, static and current. • Static Electricity: electrical charge will build up on the surface of a material. • Current Electricity: the rate of flow of electrons, produced by moving electrons.
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Charging? • There are 3 ways in which objects become charged: ▫ Friction ▫ Contact ▫ Induction
Charging by Friction • The transfer of electrons between 2 neutral objects (made of different materials) that occurs when they are rubbed together. • Causes many of the effects of static electricity • The electrostatic series determines the charge that each of the object will take on.
Electrostatic Series • The substance higher in the list will always lose the electrons and become positively charged. • Wool vs Silk • Fur vs Balloon
Static Electricity Stations
Warm-Up! Which item will become negatively charged? 1. Glass vs. wood? 2. Wool vs. Balloon? 3. Amber vs. Fur?
Charging by Contact • Transferring an electric charge from one substance to another by touching. • Charging through contact can produce an electric shock. • A spark can occur as electrons jump from your body to the object.
Conductors • Because the electricity is transferred as soon as it is produced, there is no build up of static electricity. • • • Silver Copper Aluminum Iron Gold
Electric Spark Disasters • A single spark produced by a charge transferred by contact can cause dangerous fires and explosions.
Insulators and Conductors • Electrical Insulator - a substance where electrons cannot move freely from atom to atom. • Electrical Conductor – a substance where electrons can move freely from atom to atom.
Insulators • These objects hold electrical charge and build up static charge better than conductors, however even though they hold static electricity , they can protect us from electric shock • Oil • Rubber • Plastic • Wax
Grounding? • When a charged object is connected, or grounded, to Earth, it shares its charge with the entire Earth. • This means that the charge is removed or spread out over a larger surface.
Induction • Transferring an electric charge from one substance to another without direct contact.
Charging by Contact Investigations
Warm-Up! 1. What are the 3 methods of charging an object? 2. What is the difference between an insulator and a conductor?
Read and Respond • Read pages 274 -275 • Answer questions #1 -3
Lightning https: //www. youtube. com/watch? v=G 7 Gb OFl. FODE
Lightning • When thunderclouds form, huge numbers of negative charges concentrate near the bottom of the cloud. • When the negative charge at the base of the cloud moves over tall objects, such as a building, it is sometimes close enough to return the ground in a huge spark, called lightning.
Lightning • The jagged path that lighting has is caused by the electric charges moving along the path of least resistance in the air. • Lighting tends to hit taller objects because the taller objects shortens the path to the ground, especially if they are metal conductors.
Lightning Exploration Questions 1. Why is the car the safest place to be during a lighting storm? 2. Why are golf courses, parks, and open boats dangerous places to be during a lighting storm? What would you do? 3. What happens if lighting hits you? What parts are most vulnerable? 4. What types of buildings are at risk of lighting strikes? What is done to help?
Read and Respond • Read pages 300 -301. ▫ Write definition for any bolded terms. ▫ Answer questions #1 -3 on page 301.
Current Electricity vs. Static Electricity • Static electricity is stationary or collects on the surface of an object, whereas current electricity is flowing very rapidly through a conductor.
Current Electricity • An electrical current is the flow of electrons though a wire. • The current (I) is measured in Amperes/Amps (A) • Electric current will always flow from an area of high voltage to an area of low voltage.
Voltage • The amount of electricity available to push electrons along a wire is the voltage (V), also known as the potential difference. • It is what causes a current to flow in a closed circuit.
Resistance • Resistance (R) is the opposition to the flow of an electric current, causing the electrical energy to be converted to thermal energy(heat) or light. The metal which makes up a light bulb filament or stovetop eye has a high electrical resistance. This causes light and heat to be given off.
Resistance • Measured in Ohms (Ω)
Putting in all Together Term Symbol Definition CURRENT I - the flow of electrons through a conductor VOLTAGE V - RESISTANCE R - also known as “Potential Difference” “push/force” of electricity Potential energy per quantity of electrons measures how easily electricity flows along a certain path Measured in (Units) Amperes (A) Volts (V) ohm
Ohm’s Law • The potential difference between two points on a conductor is directly related to the electric current flowing through the conductor. • V=Ix. R
Example 1 • What is the voltage drop across a tungsten filament in a 100 -W light bulb. The resistance of the filament is 144 ohms (Ω) and a current of 0. 833 A is flowing through it. • V= • I= • R=
Example 2 • An electric toaster is connected to a 120 -V outlet in the kitchen. If the heating element in the toaster has a resistance of 14 Ω , calculate the current flowing through it. • V= • I= • R=
Warm-Up! A subwoofer needs a household voltage of 110 V to push a current of 5. 5 A through its coil. What is the resistance of the subwoofer?
Circuit? • Circuits typically contain a voltage source, a wire conductor, and one or more devices which use the electrical energy. • There can be parallel and series circuits.
Interactive Activity on Circuits
Warm-Up • What is the voltage drop of a circuit with a resistance of 500 Ω that has a current of 1. 4 A flowing through it. • A 3 -V battery sends a current of 0. 10 A through a light bulb. What is the resistance of the filament of the bulb?
Drawing a Circuit Diagram
Drawing a Circuit Diagram 1. Always use a ruler to draw straight lines for the conducting wires 2. Make right-angle corners (∟) so that your finished diagrams is a rectangle • Contain 4 basic parts: – Electrical source – Switch – Load – Conducting wire
Series Circuits • Single pathway for current to flow. • If circuit breaks, all devices using the circuit will fail. •
Parallel Circuit • Multiple pathways for the current to flow. • If circuit is broken, current may pass through other pathways and other devices will continue to work.
Short Circuit • A short circuit is an accidental lowresistance connection between two points in a circuit, often causing excess current flow.
Warm-Up! 1. Draw a proper electrical circuit diagram. 2. Are the bulbs in parallel or series? 3. Draw a circuit diagram in the opposite configuration.
Drawing Electric Circuits Practice 1. Battery (3 cells), two light bulbs and a switch that controls both light bulbs. 2. Battery (2 cells), one light bulb, one resistor, and another light bulb. 3. Battery (4 cells), switch, and three light bulbs. 4. Try this: battery (3 cells), two light bulbs and a switch that only controls one of the light bulbs.
Lab on Parallel and Series Circuits
Review of Electricity Unit!
Question One • A negatively charged object is repelled by another. What is the charge of the other object?
Question Two • A negatively charged object is attracted by another. What is the charge of the other object?
Question Three • What is the symbol for a closed switch? • What is the symbol for an open switch?
Question Four • What is the symbol for a light bulb? • What is the symbol for a battery?
Question Five • V=Ix. R • What voltage is required for 15 A to run through 5Ω
Question Six • V=Ix. R • What is the resistance of a 20 V circuit with 5 A?
Question Seven • V=Ix. R • What is the current of a 30 V circuit with a resistor of 6Ω?
Question Eight • What are the 3 methods of charging a neutral object?
Question Nine • Draw a parallel circuit with 3 light bulbs. The switch must control only 2 lightbulbs.
Question Ten • What does grounding mean?