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Science Grade 9 Academic Exam > Electricity > Flashcards

Electricity Flashcards

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0
Q

Effects of Resistance in Circuits

A

Length: longer wire, greater resistance

Temperature: Hotter wire, greater resistance

Thickness/Diameter: Thicker wire, lower resistance

Type of material

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1
Q

Potential Difference - Water Analogy

A

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.

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2
Q

Current

A

Rate of charge flow

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3
Q

Potential Difference

A

Difference of potential energy when measure of work per unit charge between 2 points in a circuit.

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4
Q

Loads in Series

A

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.

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5
Q

Loads in Parallel

A

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.

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6
Q

What remains all the same in Series

A

Current (I)

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7
Q

What remains the same in Parallel?

A

Voltage (V)

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8
Q

Law of Electric Charge

A

Like charges repel, unlike charges attract, charged objects attract neutral objects.

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9
Q

Objects that hold a charge

A

Combs, rulers, clothing, airplanes, clouds

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10
Q

Objects that DO NOT Hold a Charge

A

Hair, rubber balloon

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11
Q

Static Electricity

A

An imbalance of electric charge on the surface of an object.

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12
Q

Current Electricity

A

The controlled flow of electrons through a conductor.

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13
Q

Conductors

A

Material that allow electrons to flow through it

Ex: metals (silver, gold, aluminium, copper, iron)

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14
Q

Semiconductors

A

Materials somewhere in between insulators & conductors

Ex: graphite-carbon, human body, damp skin, salt water, silicon, earth

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15
Q

Insulator

A

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)

16
Q

Pros: Hydro-Electric

A

Doesn’t produce pollution

Uses vast amount of concrete, steel, specialized machinery, fossil fuel resources

Long-lasting, electricity produced at a constant rate

17
Q

Pros: Tidal

A

Renewable, emission-free, high efficiency

18
Q

Pros: Thermal

A

Loads of employment opportunities

19
Q

Pros: Wind

A

Significantly cheaper compared to other methods

Short transmission lines, minimizing electricity loss

20
Q

Pros: Sunlight

A

Long-lasting, maintenance- free

Can be operated independently of the power grid or not

21
Q

Cons: Hydro-Electric

A

Uses dams, changing the way water flows

Disrupts migration of fish and flood large areas of land

Very expensive

Limited suitable locations available

22
Q

Cons: Tidal

A

Built near coastlines that experience significant changes in tide

23
Q

Cons: Thermal

A

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

24
Q

Cons: Wind

A

Noisy, dangerous to birds

Difficult to generate steady electricity supply at particular locations

25
Q

Cons: Sunlight

A

30% efficient at converting Sunlight

Expensive

Time-consuming to produce elctricity

26
Q

Electric Cell

A

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

27
Q

Fuel Cell

A

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

28
Q

Uses of Static Electricity: Electrostatic Applications

Paint Sprayers

A

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

29
Q

Uses of Static Electricity: Electrostatic Applications

Precipiators

A

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.

30
Q

Uses of Static Electricity: Electrostatic Applications

Lifting Apparatus

A

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

31
Q

Uses of Static Electricity: Electrostatic Applications

Speakers

A

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

32
Q

Electric Discharge

A

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.

33
Q

Lightning

A

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.

34
Q

Alternating Current AC

A

Flow of electrons that alternates in direction in an electric circuit, produced by electric cells

35
Q

Direct Current DC

A

Flow of electrons in one direction through an electric circuit, produced in generating plants

36
Q

Basic Components of an Electric Circuit

A

Load - converts electrical energy into other forms of energy

Switch - controls flow of electrons by opening/closing circuit

Electric Cell/Battery - Energy source

37
Q

3 ways to reduce electricity consumption at home

A

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

Science Grade 9 Academic Exam (4 decks)

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