Electricity-Robo-9
Page 3: Benjamin Franklin
Franklin proved that lightning and the spark from amber were the same thing.
Page 4: Galvani and Volta
Luigi Galvani found that when the leg of a dead frog was touched by a metal knife, the leg twitched violently.
Galvani thought that the muscles of the frog must contain electricity.
Alessandro Volta disagreed with Galvani and realized that the main factors in Galvani's discovery were the two different metals - the steel knife and the tin plate - upon which the frog was lying.
Volta showed that when moisture comes between two different metals, electricity is created.
Volta invented the first electric battery, the voltaic pile, made from thin sheets of copper and zinc separated by moist pasteboard.
Page 5: Michael Faraday
Faraday discovered that when a magnet was moved inside a coil of copper wire, a tiny electric current flows through the wire.
Page 6: Edison and Swan
Thomas Edison built a practical DC (Direct Current) generator.
Joseph Swan invented the incandescent filament lamp, and Edison made a similar discovery in America.
Page 7: Westinghouse and Tesla
Westinghouse purchased and developed Nikola Tesla's patented motor for generating alternating current.
Westinghouse and Tesla persuaded Americans that the future lay with AC rather than DC.
Page 8: James Watt
Edison's generator coupled with Watt's steam engine made large-scale electricity generation practical.
James Watt invented the steam condensing engine and his name was given to the electric unit of power, the Watt.
Page 9: Ohm
George Simon Ohm published "The Galvanic Circuit Investigated Mathematically" in 1827.
Ohm's research was recognized in Britain, and he was awarded the Copley Medal in 1841.
Ohm's name has been given to the unit of electrical resistance.
Page 11: Electricity
Electricity is a form of energy from the movement of electrons.
The word "electricity" comes from the Greek word "elektron," which means amber.
Page 12: Electricity
Electricity is associated with electric charge, a property of subatomic particles.
Charges can be stationary or moving.
Page 13: Electricity
Unlike charges attract, and like charges repel.
Page 14: Static Electricity
Static electricity is the temporary building up of charge on an object.
Some atoms hold electrons more tightly than others.
Page 15: Insulators and Conductors
Some materials allow charges to be transferred (conductor), while others do not (insulator).
Page 16: Insulators and Conductors
Conductors: Gold, Silver, Copper, Iron, Lead, Salt Water.
Insulators: Plastics, Glass, Dry Air, Wood.
Page 17: Electric Current
Electric current is the flow of charges.
The electric charge in a current is carried by minute particles called electrons.
Page 18: Electric Current
For electricity to flow, a closed continuous path called a circuit is needed.
Page 19: Current
Current is the measure of how many electrons per second.
Current is also called amperage and is measured in amperes.
Page 20: Measuring Electric Current
An ammeter is used to measure electric current.
The SI unit for electric current is ampere (A).
1A = 1000 mA, 1mA = 0.001A.
Current = charge / time (I = q / t).
Page 23: Types of Currents
There are two types of currents: Direct Current (DC) and Alternating Current (AC).
DC is where electrons flow in the same direction in a wire (e.g., batteries).
AC is where electrons flow in different directions in a wire (e.g., electricity in the home).
Page 25: Voltage
Voltage is the push that causes electrons to flow.
Voltage is measured in volts (V).
Page 26: What is Voltage?
Voltage is the measure of energy given to the charge flowing in a circuit.
Voltage = Current x Resistance.
Page 31: Voltmeter
A voltmeter is an instrument used for measuring voltages.
It is connected in parallel across the cell.
It has a positive (red) terminal and a negative (black) terminal.
Page 32: Resistance
Resistance is the tendency for a material to oppose the flow of electrons.
Different materials have different amounts of resistance.
The unit of resistance is ohm (Ω).
Page 33: What Influences Resistance?
The material of the wire, thickness, length, and temperature influence resistance.
Page 35: Resistance
Resistance can be measured by dividing voltage by current (R = V / I).
Page 36: Ohm's Law
Ohm's Law states that current is directly proportional to voltage and inversely proportional to resistance (I = V / R).
Page 38: Circuits
Components like cells, wires, switches, and lamps are connected together with metal connecting wires to form a circuit.
Page 39: Circuits
When the switch is turned on (closed), the lamp lights up because there is a continuous path of metal for the electric current to flow around.
Page 41: Circuits
Scientists usually draw electric circuits using symbols.
Page 43: Types of Circuits
There are two types of circuits: series and parallel.
Page 44:
Series circuits:
Components are connected end-to-end, one after the other.
Creates a simple loop for the current to flow.
If one bulb 'blows', it breaks the whole circuit and all the bulbs go out.
Page 45:
Parallel circuits:
Components are connected side by side.
Current has a choice of routes.
If one bulb 'blows', there is still a complete circuit to the other bulb so it stays alight.
Page 46:
Circuit diagrams:
Components are represented by symbols.
Symbols include cell, battery, switch, lamp, ammeter, voltmeter, motor, buzzer, resistor, and variable resistor.
Page 47:
Measuring Current (Series):
Current is the same at all points in the circuit.
Current is constant.
Page 48:
Measuring Current (Parallel):
Current is shared between the components.
Current is the sum of the currents in each component.
Page 49:
Measuring Voltage (Series):
Voltage is shared between the components.
Voltage is the sum of the voltages across each component.
Page 50:
Measuring Voltage (Parallel):
Voltage is the same at all points in the circuit.
Voltage is constant.
Page 51:
Measuring Resistance (Series):
Resistance is shared between the components.
Total resistance increases because all of the current must go through each resistor.
Page 52:
Measuring Resistance (Parallel):
Total resistance is computed using the equation: 1/R = 1/R1 + 1/R2 + 1/R3.
Page 53:
Example 1:
Given battery voltage of 12V, voltage across R1 is 5V, and voltage across R2 is 4V.
Find the voltage across R3.
Page 54:
How to Solve a Series Circuit (Easy):
Given circuit with resistors R1, R2, and R3.
Solve for total resistance, total current, and voltage drop at each resistor.
Page 55:
How to Solve a Series Circuit (Easy):
Given circuit with resistors R1, R2, and R3.
Solve for total resistance, total current, and voltage drop at each resistor.
Page 56:
Parallel Circuits:
Current is the sum of the currents in each component.
Voltage is the same across each component.
Use Ohm's Law to calculate voltage and current.
Page 57:
Example:
Given circuit with resistors R1, R2, and R3.
Solve for resistance, current, and voltage.
Page 58:
Example:
Given circuit with resistors R1, R2, and R3.
Solve for resistance, current, and voltage.
Page 59:
Example A:
Load across a 50.0V battery with two lamps in series.
Find total resistance, total current, voltage across each lamp.
Page 60:
Example B:
Load across a 12V battery with three resistances in parallel.
Find total resistance, total current, current of each load, voltage of each resistor.
Page 61:
Example C:
Resistors connected in parallel and connected to a 35V battery.
Draw circuit diagram, find total resistance, voltage of the circuit, current of each load, total power of the circuit.
Page 63:
Power:
Rate at which energy is flowing.
Measure of the rate at which electricity does work or provides energy.
Symbol = P, Units = Watts (W).
Power = Current x Voltage.
Page 64:
Electrical Energy:
Home use of electric energy is based on the amount of electrical power used per hour.
Measured in kilowatt hours (kWh).
Electrical Energy = Power x Time.
Page 65:
Electrical Energy Example:
Using a hairdryer for 20 minutes every day.
Hairdryer uses 1000 kW.
Calculate the kilowatt-hours used in 6 days.
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