Science Section 2 Academic Decathlon 25-26

James Joule

Connection between heat & work

William Thomson

"Lord Kelvin"

Laws of Thermodynamics

1st Law of Thermodynamics

Conservation of energy

2nd Law of Thermodynamics

Kinetic energy exchange

Always goes high to low

3rd Law of Thermodynamics

No system can reach absolute zero

Kinetic Energy

Moving energy

Flow of kinetic energy

Nuclear reactions in suns core -> sunlight -> food chain -> energy in muscles -> throwing ball -> sound; vibrations; air compression

Heat

Energy in transit between objects at different temperatures

Can only emit or absorb heat, not contain it

Phlogiston

Formerly thought to be the heat being exchanges (own substance)

Now understood that heat is a property inherent in materials

Temperatures

Average kinetic energy of the atoms in a substance

Fast moving transfers energy into slow moivng

Zero temperature

Atoms in a substance are not moving at all

Nothing lower than zero, so no way to cool it off more

Gravitational potential energy

Energy that an object possesses due to its position in a gravitational field

Electric potential energy

No gravity and a negatively charged floor with a positive pendulum

Pos pendulum is pulled towards negative floor

Same as gravity

Proportional to charge

Voltage

Differences in electric potential

Electric Potential

Electric Potential Energy/Charge

Measured in volts or joules per coulomb

Environment around object

Describes how the electric field changes across some distance

Cannot be directly measured (Instead, voltage across 2 points)

Equipotential line

Indicates steepness (strength) of electric field

ΔE=q*V

Alessandro Volta

Invented a modern battery

Volts named after him

"Battery"

Formerly a military term for a coordinated group of artillery weapons

Inspired Ben Franklin's name for connected Leyden Jars

"Piles"

Lucia and Luigi Galvani

1780s, during a dissection of a frog (later, any dead body) the body jumped when touched with two different metals

Conclusion: Movement of dead frog was due to electricity within it, activated by metals

Actual: Acids in frogs skin dissolved metals, electrons transferred

Galvanism

Electricity = life force?

Volta and Galvansism

Electricity came from the metals, not the corpse

Tested with silver and zinc sheets with saltwater soaked cardboard -> 30 volts created

Giovani Aldini

Nephew of Lucia and Luigi Galvani

Left hemisphere controls the right side of the body, vise versa

Electroshock can cure depression

Modern battery

Device that maintains a constant voltage by keeping two collections of positive ad negative charge separate from each other

Carbon Electrode (+), Zinc Electrode (-), Sulfuric Acid

Acid dissolves zinc, gains + charge while Zinc is -

+ Acid polarizes carbon rod so it's - in Acid and + outside

Wire connect terminals, positive charge flows to neutralize negative

Acid-> allows terminals to recharge and maintain imbalance

Zinc will eventually corrode

Primary cell batteries

Disposable, one-use batteries

Secondary cell batteries

Can be recharged

Lithium Ion Battery

Move lithium ions through a conducting chemical fluid

When charging, the terminals switch, so the ions flow to the other side

Heat is generated through friction, transferred to surroundings (takes energy) - fire

Phones, cars

Electric Circuit

Closed loop in which energy continuously flows

Positive energy tries to neutralize negative energy in battery, connected by wire - but battery maintains charge separation

Direct Current (DC), no changes in direction

Battery keeps charge from gathering at an area of low potential

Voltage

Electromotive force (EMF)

Tells how powerful the circuit will be

Flow of electricity

the ELECTRONS are moving

when we say that a charge is flowing (positive), the electrons are moving in the opposite direction

Electric current

measuring the amount of charge that flows past a point per second

measured in Amperes

André-Marie Ampére

Namesake for Amperes (amps)

Amperes

Measure of electric current

1 amp = 1 coulomb / sec

Effect of Amps

0.001 = Shock

0.005 = Painful Shock

0.015 = Loss of Muscle Control

0.070= Fatal

Why are Amps dangerous

They disrupt the electric signals in your body

Electrocardiogram (EKG)

Measured voltage across parts of the body to measure heartbeat

When heart is beating too fast, doctors stop it so that the body starts it again (pacemaker)

Electrophysiology

Study of electricity in the human body

Frankenstein by Mary Kelly

Inspired by demonstrations of electric shocks & corpses

Ohm's Law

Measure current in a circuit

Ohm's Law Equation

V= Battery Voltage; I= Current; R= Resistance

Resistance (R)

Resists the flow of the current

Measured in ohms (Ω)

Conductive=low, insulation=high

Long wire>short wire

High voltage

Rubbing a balloon

"Height" that the charges in a circuit "fall" down from high potential (+) to low potential (-)

Any charge that flows will be building up energy BUT it depends on the amount of charged particles

Creates the conditions for the current

POTENTIAL difference

High current

What affects you

120 V in wall outlet

Power

Rate of energy change over time

Measured in watts

Watts

Measures power

1 watt=1 joule/second

Lightbulb

Wire that has a current will heat up enough to glow

Tungsten filament in an incandescent lightbulb

2000 Celsius, glows Yellow

Kilowatt Hour

3,600,000 joules

Resistance & Temperature

Increasing in current causes an increase in temperature, which leads to an increase in resistance

Superconductors

Resistance is zero

Resistor

Resists current by taking energy away from the flow of charge into another form of energy