QUICK WRITE: For 2 minutes, write in your IAN explaining where electric charges come from and why. Rules - You MUST write for the entire time, even if you write the exact same thing over and over again!
Protons = ______ Charge Electrons = _________ Charge Neutrons =__________ Charge When Protons = Electrons, atoms are said to be ELECTRICALLY NEUTRAL (no net charge)
At your table, determine whose First Name comes LAST in the alphabet. That person will talk first in the TABLE TALK! You will be comparing and contrasting Conductors and Insulators. Each person will get 20 seconds to talk and MUST talk the WHOLE TIME. I will signal when each person should start and stop. Finally, you will SHARE your discussion with the class.
Conductors and Insulators Conductors – objects in which electrical current easily passes through such as metals Insulators – objects that resist the flow of electrical current such as plastic, wood, paper, and rubber
Where is the conductor in this picture? How do you know?
Where is the insulator in this picture? How do you know?
The flow of ELECTRONS through a conductor.
Causes of Force 1. Distance between the charges 2. Amount of charge
SI Unit of charge is Coulomb [C]
What do these two pictures have in common? Talk with your partner for 30 seconds and BE PREPARED TO SHARE!
The accumulation of excess electric charge. (not balanced) Ex. Lightning What about in water?
Quick Write: Which is stronger electric force or gravitational force? How do you know? Defend your choice. Share your choice with the class!
Let’s find out!
The correct answer should be the Electric Force! Why? Because like you witnessed in the video the electric force can overcome the gravitational pull of the Earth; and the Strong Electric Force is responsible for holding together the protons and neutrons in the nucleus of an atom. An atom’s nucleus can only be split by nuclear fusion, which cannot be done on Earth and gravity can’t do this!
Which of the following objects is a good conductor? A. Water B. Rope C. Copper D. Plastic
Which type of force is strongest? A. Gravitational force B. Electrical Force
Which of the following balloon configurations depict the correct charges of the balloon and wall?
The imbalance of an electrical charge is also known as: A. Charged electricity B. Static Electricity C. Contact Electricity D. Negative Electricity
ELECTRICAL CIRCUITS
+ - What is this a picture of?
What is electric current? Conventional current Electric Current (I) - a flow of electrons from the (+) terminal to the (-) terminal of a cell/battery through wires and components + -
Electric Field Electric Field – when the electrons of a current are in motion, lines of electric force rotate around the electron, or between two charges.
Does your picture provide Light or No Light? Do you know WHY?
Open and Closed Circuits Open circuit = switch is open = no current is flowing = bulb does not light Closed circuit = switch is closed = current is flowing = bulb lights up
Circuit Diagram & Symbols Cell/Battery Switch Light Bulb Wires Light Bulb Resistor Resistor
Draw a picture of a SERIES Circuit. Show a battery and a light bulb in your drawing. Draw a picture of a PARALLEL Circuit. Show a battery and TWO light bulbs in your drawing. Be prepared to discuss your pictures.
Types of Circuits Series Circuits – current takes only one path and is the same at each point. (One Wire connects ALL)
Series Circuits If one bulb blows out, it breaks the circuit and all the bulbs go out If you add more cells/batteries to a series circuit, the bulbs burn brighter
Types of Circuits Parallel Circuits – current takes more than one path and is NOT the same at each point. (Multiple Wires)
Parallel Circuits If one bulb blows out, there is still another complete circuit for the other bulb to stay lit
A – Parallel B – Series Draw these circuits in your Notebook. Label each one as either Series or Parallel.
Conductor or Insulator? Conductor
Brighter or Dimmer? Dimmer
Series or Parallel? Series
Brighter or Dimmer? Brighter
Series or Parallel? Parallel
Series or Parallel? Series
Series or Parallel? Parallel
Ohm’s Law
What happens to the Resistance when the Current is doubled and the Voltage stays the same? The Resistance is halved!
What will happen to the Voltage when the Resistance is tripled and the Current remains constant? The Voltage is Tripled too!
What happens to the Current when the Resistance is reduced by 1/3 and the Voltage stays the same? The Current is Tripled!
Measuring Current Current is measured in units of amperes (A) In a series circuit, current is the same at all the points In a parallel circuit, current is shared between all the points 2A 1A 2A
1A What is the current? SERIES CIRCUIT PARALLEL CIRCUIT 3A 1A 3A 4A
Measuring Voltage Voltage – the electrical push that a cell/battery gives to the current Voltage is also known as Potential Difference Voltage is measured in units of volts (V)
In a series circuit, voltage is shared between all the points In a parallel circuit, voltage is the same at all the points 1.5V 3V Measuring Voltage
V V 6V 4A A A 3V 6V 4A CurrentVoltage SeriesSameShared ParallelSharedSame What is the current and voltage?
V V 6V 4A A A A 6V 4A 2A
Measuring Resistance Resistance – slows down current, adding components to a circuit increases resistance Resistance is measured in units of ohms ( Ω ) More resistance = Less current = Less light In a series circuit, add up all resistance to get total.
Electrical Power
How much voltage gives 5 amps of current through a 3 Ω light bulb? I = V/R V = (5A) (3Ω) V = 15V
How much current flows in a circuit with a 1.5 volt battery and three 1 ohm resistances (bulbs) in series? I = V/R I = (1.5V) / (3Ω) I =.5A
What is the voltage drop across each resistor in the circuit? 9V/3 = 3V In a series circuit, voltage is shared between all the points
A light bulb with a resistance of 1.5Ω is connected to a 1.5V battery in the circuit. Calculate the power used by the light bulb? P = IVI = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A) (1.5V) = 1.5 W P = 1.5 W