Electricity Flashcards
Effects of Resistance in Circuits
Length: longer wire, greater resistance
Temperature: Hotter wire, greater resistance
Thickness/Diameter: Thicker wire, lower resistance
Type of material
Potential Difference - Water Analogy
Energy of falling water used to push waterwheels because water above wheel has greater gravitational potential energy than it does below wheel. Steady supply of water is needed to keep wheel spinning. As water’s pumped to its original position, its gravitational potential energy also increase to original amount.
Similarly, there’s potential difference between 2 terminals of an electric cell. Electrons leave negative terminal w/ electric potential energy to operate a motor. Electrons return to positive terminal w/ less electric potential energy since some energy was used to run the motor. Once inside cell, chemical reactions ‘re-energize’ electrons & send them out megative terminal again.
Electric cell acts like the water pump.
Current
Rate of charge flow
Potential Difference
Difference of potential energy when measure of work per unit charge between 2 points in a circuit.
Loads in Series
More bulbs, dimmer bulbs.
Same amount of energy has to be distributed throughout even more loads, each with less energy.
Same voltage applied over greater resistance, decreasing the current / brightness.
Loads in Parallel
More bulbs, same brightness.
Different branches for electrons to flow through to get to each load with each load having the same amount of voltage so it wouldn’t make a difference.
What remains all the same in Series
Current (I)
What remains the same in Parallel?
Voltage (V)
Law of Electric Charge
Like charges repel, unlike charges attract, charged objects attract neutral objects.
Objects that hold a charge
Combs, rulers, clothing, airplanes, clouds
Objects that DO NOT Hold a Charge
Hair, rubber balloon
Static Electricity
An imbalance of electric charge on the surface of an object.
Current Electricity
The controlled flow of electrons through a conductor.
Conductors
Material that allow electrons to flow through it
Ex: metals (silver, gold, aluminium, copper, iron)
Semiconductors
Materials somewhere in between insulators & conductors
Ex: graphite-carbon, human body, damp skin, salt water, silicon, earth
Insulator
Material that DOES NOT allow electrons to flow through
Ex: non-metals (oil, fur, wool, silk, rubber, glass, plastic, pure water, ebonite, wax, paper, wood)
Pros: Hydro-Electric
Doesn’t produce pollution
Uses vast amount of concrete, steel, specialized machinery, fossil fuel resources
Long-lasting, electricity produced at a constant rate
Pros: Tidal
Renewable, emission-free, high efficiency
Pros: Thermal
Loads of employment opportunities
Pros: Wind
Significantly cheaper compared to other methods
Short transmission lines, minimizing electricity loss
Pros: Sunlight
Long-lasting, maintenance- free
Can be operated independently of the power grid or not
Cons: Hydro-Electric
Uses dams, changing the way water flows
Disrupts migration of fish and flood large areas of land
Very expensive
Limited suitable locations available
Cons: Tidal
Built near coastlines that experience significant changes in tide
Cons: Thermal
Burning of fossil fuels contribute to climate change
Increase Earth’s temperature due to radiation of carbon dioxide
Produces air pollution and destroys natural habitats
Cons: Wind
Noisy, dangerous to birds
Difficult to generate steady electricity supply at particular locations
Cons: Sunlight
30% efficient at converting Sunlight
Expensive
Time-consuming to produce elctricity
Electric Cell
Produces small quantity of electrical energy, useful for portable electrical devices
Has 2 electrodes (conductors) called an electrolyte
1 electrode can be positive and the other, negative
When ends are joined to conducting wires of a circuit, electrons begin to flow through from one electrode to the other
Electrons in electrolyte are repelled by negative electrode and attracted to the positive electrode
Electrons pass from negative to positive terminal
All electric cells contain chemicals that are toxic to the environment, could damage naturals surroundings - should be properly recycled
Fuel Cell
Special kind of electric cell that requires a continuous supply of fuel (i.e., hydrogen, oxygen) to provide electrical energy
Any waste products are removed during the process
Can operate longer than conventional/typical electric cell
Hydrogen used in most fuel cells must be removed from compounds rich in hydrogen i.e.m fossil fuels. This process uses lost of energy creating pollution & contributes to climate change
Uses of Static Electricity: Electrostatic Applications
Paint Sprayers
Reduce amount of wasted paint, efficiently paint objects especially curved shaped
Paint given a charge as it leaves nozzle of sprayer and object to be painted is given opposite charge. Charged paint particles attract to object, minimizing amount of wasted paint & ensuring object receives an even coat of paint
Uses of Static Electricity: Electrostatic Applications
Precipiators
Remove particles from air, filter particles from smokestack emissions
When smoke passes through negatively charged plates, particles in smoke become negatively charged by conduction. Particles then pass between positively charged plates, which they stick to, due to attraction of opposite charges. Particles fall onto collection plate, safely removing them.
Uses of Static Electricity: Electrostatic Applications
Lifting Apparatus
Make copies of footprints (for investigation)
Special film/foil placed over footprint, black side placed over footprint.
Film is then electrostatically charged, dust & dirt particles from footprint are attracted to black side
Dust particles jump off floor onto black film, revealing details of footprint
Uses of Static Electricity: Electrostatic Applications
Speakers
Constructed of 3 thin layers, outer 2 called stators are fixed in place
Inner layer is flexible film called, diaphragm which vibrates to produce sound
Accomplished using principles of induction and law of electric charges
Inner surface given permanent electrical charge
Audio transformed used to induce opposite charges in 2 outer plates.
Causes diaphragm to move as it’s attracted to 1 outer plate and repelled by the other.
Audio transformer then rapidly induces static charges in outer plates to reverse themselves. This causes diaphragm to move toward opposite outer plate. Reversing of charges on outer plates happens repeatedly and at variable frequencies causing diaphragm to rapidly vibrate back and forth between plates, producing sound waves in air
Electric Discharge
Rapid transfer of electrons from one object to another
When 2 objects that have a charge imbalance are brought close together or some in contact, electrons are transferred from one object to another.
Electrons always move from object w/ more negative charge to object w/ less negative charge.
Lightning
When water droplets in clouds move past one another, they become charged. Electrons are transferred from rising water molecules to falling water droplets.
Negatively charged water molecules collect at bottom of cloud. Excess negative charge at bottom of cloud repels electrons at Earth’s surface. Electrons move away from area on Earth’s surface near cloud, causing it to become positively charged. Results in a charge imbalance.
Alternating Current AC
Flow of electrons that alternates in direction in an electric circuit, produced by electric cells
Direct Current DC
Flow of electrons in one direction through an electric circuit, produced in generating plants
Basic Components of an Electric Circuit
Load - converts electrical energy into other forms of energy
Switch - controls flow of electrons by opening/closing circuit
Electric Cell/Battery - Energy source
3 ways to reduce electricity consumption at home
Turn off appliances & lights whenever you leave home
Unplug chargers when not charging
Cutting heating needs, insulate walls and ceilings instead
Switching to solar energy
