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Gr.9 > Sci (Current Electricity) > Flashcards

Sci (Current Electricity) Flashcards

1
Q

Electricity:

A
  • Is a general term that refers to electric charge - when an atom does not have = p+ and e-
  • Can be either static electricity or current electricity
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2
Q

Current Electricity:

A

Is electric charge in motion (the charges moves continuously along a path).

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3
Q

Generating Electrical Current:

A

REMEMBER: Energy cannot be created or destroyed, it can only change forms. Also, everything in the universe is matter OR energy.
- Chemical Potential Energy
- Kinetic Energy
- Thermal Energy
- Solar (light) Energy
- Piezoelectric

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4
Q

Chemical Potential Energy:

A
  • Is the energy stored in the chemical bonds of a substance. This energy can be stored within atoms, molecules, and chemical bonds that make up matter.
  • Turns chemical potential energy into electrical energy.
  • Devices used: batteries - electrical cells; primary or secondary, AND fuel cells
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5
Q

Kinetic Energy:

A
  • Is the energy an object has because of its motion.
  • Devices used: wind turbine, water turbine; drive generators which use magnetism (coiled wire in magnetic field) to push.
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6
Q

Thermal Energy:

A
  • Burning releases thermal energy (chemical potential energy converted to kinetic energy converted to electrical energy).
  • The heat is used to boil water - steam rotates a turbine to generate electricity.
  • For example: fossil fuels (chemical potential energy - breaks bonds), nuclear (nuclear reaction splits nuclei (uranium)), biomass (chemical potential energy - breaks bonds).
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7
Q

Solar (light) Energy:

A
  • Any type of energy generated from the sun, or light sources.
  • Device - photovoltaic cells (in solar panels).
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8
Q

Piezoelectric:

A

When a crystal is squeezed forcing negatively charged atoms in one direction. If the crystal is connected to a conductor a current results. Sound waves can squeeze a crystal eg) rochelle salt quartz.

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9
Q

Renewable Energy Source:

A

Natural energy resource that is unlimited (for example, energy from the sun or wind) or can be replenished by natural processes in a relatively short period of time (ex. biomass). Ex. Waves and wind.

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10
Q

Non-Renewable Energy Source:

A

A resource that cannot be replaced as quickly as it is consumed. Ex. Coal, Oil, Uranium, and Natural gas.

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11
Q

Hydroelectric Power (Dam):
Pros & Cons

A
  • Pros: does not pollute air/water, creates large volumes of falling water, clean and sustainable, water carries big amounts of energy, and it’s a renewable energy source.
  • Cons: migration of fish is disrupted, large areas of land may become flooded, costly and has many ‘invisible’ costs, not all places are suitable for hydroelectric plants.
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12
Q

Tidal Energy:

A

The Generation Cycle is how the tide occurs twice daily at specific times in a cycle. Tidal generation stations can only operate as the tide comes in, or goes out. The station is on for 5 hours and off for 7 hours. The cycle repeats when the tide changes from low tide to high tide.

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13
Q

Tidal Energy:
Pros & Cons

A

-Pros: no pollution, renewable energy source, high power output, zero emissions, and predictable energy generation.
- Cons: only built near coastlines that experience significant change in tide, expensive to operate, negative effects on plants, animals, and ecosystems.

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14
Q

Fossil Fuels:

A
  • Fossil Fuels are non-renewable sources. They were formed from plants, animals, and micro-organisms that lived millions of years ago. Ex. Coal, oil, and natural gas.
  • When fossil fuels are burned, they provide significant amounts of energy. They are an important resource for energy production.
  • They release large amounts of greenhouse gases which cause things like climate change.
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15
Q

Fossil Fuels:
Pros & Cons

A
  • Pros: produce significant amounts of energy, when coal is used in power plants it is cost effective, they can be found easily, easy to store and transport.
  • Cons: non-renewable sources, irresponsible use could result in danger, emit greenhouse gases.
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16
Q

Nuclear Power:

A

The nuclei of the atoms break apart and release huge amounts of energy. This energy is used to heat water, producing steam. Thermal generation includes biomass to generate electricity.

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17
Q

Nuclear Power:
Pros & Cons

A
  • Pros: clean energy and reliable source, creates many jobs, carbon free electricity, high power output, small carbon footprint.
  • Cons: expensive initial cost, malfunctions can be catastrophic, limited fuel supply, uses non-renewable sources, high radioactivity.
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18
Q

Light (Solar) Power:

A
  • A photovoltaic cell is a device that converts light directly into electrical energy. One type of cell is the solar cell. It captures energy from the sun and converts it into electrical energy.
  • Sunlight shining on this cell creates a flow of electrons.
19
Q

Light (Solar) Power:
Pros & Cons

A
  • Pros: installed in any sunny location, does not pollute air or water, renewable; sunlight, maintenance is free when properly installed, lasts more than 40 years.
  • Cons: only about 30% efficient, solar panels are expensive, doesn’t produce large amounts of electricity immediately, needs several hours of sunlight,
20
Q

Future of Energy Production:

A
  • Electricity generated in Ontario includes nuclear, hydro, coal, natural gas, and wind.
  • Turbines and generators provide different purposes. A generator is attached to a turbine. The turbine requires an external source such as wind to push the blades and rotate the generator. The generator then converts the energy into electrical energy.
  • Sources commonly used for thermal generation are fossil fuels, radioactive materials, plant and animal materials, thermal energy in earth’s crust, and sunlight.
21
Q

The key parts of a generator system

A

They are the turbine, shaft, and coil of wire inside the magnet. They are used to convert kinetic energy into electrical energy.

22
Q

Most electrical energy used in Canada is generated from:

A

Hydroelectric, nuclear, and biomass.

23
Q

Environmental impacts should be considered when

A

assessing an energy source for its pros and cons.

24
Q

Turbine -

A

Part of a generator system

25
Q

Geothermal -

A

Heat from below Earth’s surface

26
Q

Fossil fuels -

A

Took millions of years to form on Earth

27
Q

Uranium -

A

Formed in explosions of stars before the Earth formed

28
Q

Hydroelectric energy -

A

Is generated by moving water

29
Q

Coal -

A

A type of fossil fuel

30
Q

Circuit Info:

A
  • The more bulbs in a circuit, the dimmer they become as they are sharing the current.
  • The more bulbs in a parallel, the brightness remains the same.
  • When there’s an open switch in a parallel, only the devices not directly connected to the power source will turn off.
31
Q

Types of Circuits:

A
  • Series Circuit
  • Parallel Circuit
  • Mixed Circuit
32
Q

Series Circuit:

A

Has only one path for the current to flow. All the electrons in the circuit follow the SAME path. As the load increases, the current decreases. When one bulb burns out, the current stops.

33
Q

Parallel Circuit:

A

Has two OR MORE pathways (BRANCHES) for current to flow. Electrons can follow different paths or branches.The current splits into parts - part of the current goes through each bulb. The current increases as more bulbs are connected.

34
Q

13.3 Electric current:

A
  • Current is a measure of the rate of electrons flow, past a given point in a circuit. Current is measured in amperes (Andre-Marie Ampere) (A) by using a device called an ammeter.
  • Ammeters must be connected in series with a load when measuring current.
  • Circuit breakers and fuses protect electrical devices from excess current.
  • When an electric circuit does not work, you troubleshoot the circuit using an ammeter.
  • Very large currents can damage electrical devices and cause an electrical fire. This is why every home has a distribution panel with circuit breakers or in older homes, fuses.
  • If there is too much current through the circuit breaker or fuse, it trips or blows and acts as an open switch.
35
Q

13.5 Potential difference:

A
  • Potential difference, or voltage, is the difference in electric potential energy per unit charge measured at two points. Electrons flow from a point of higher electric potential energy to a point of lower electrical potential energy.
  • Potential difference is measured in volts (V) using a device called a voltmeter. Voltmeters must be connected in a parallel with either a load or an energy source when measuring potential difference.
36
Q

13.7 Resistance:

A
  • Electrical resistance is the ability of a material to oppose the flow of electric current, measured in ohms using ohmmeters.
  • Materials that have less resistance are usually used as conductors.
  • Resistance causes electrical devices to warm up when a circuit is functioning.
  • Resistors are electrical devices that affect the electric current in a circuit.
  • Ohmmeters are connected in parallel with a load when measuring resistance. The circuit must be turned off to measure the resistance.
37
Q

13.9 Laws of Electricity:

A
  • Ohm’s law states that as the potential difference across a load increases, so does the current.
  • The current through a load depends on its resistance and the voltage drop across it.
38
Q

OPG:

A
  • Most of Ontario’s electricity generating stations are located in the southern half Close to where demand for power is greatest.
  • The main function of a powerstation is to transform kinetic energy into a flow of electrons or electricity.
  • Electricity needs to be consumed as it is generated. There is no economical way to store large quantities of electricity for later use.
  • The constant steady demand for electricity is called base load demand. In Ontario, our base load demand for electricity is 11,000-15,000 MW depending on the times.
  • The demand for electricity varies throughout the day. Between 4pm-7pm as people arrive home, demand for electricity is at its highest. This is called peak demand.
  • To meet the sharp increases in electricity demand, Ontario uses thermal generating stations like coal, oil, and natural gas plants as well as small hydroelectric stations.
39
Q

Kirchoff’s Law:

A
  • Gustav Kirchoff developed a set of rules which deal with current and energy within circuits. Known as KCL and KVL.
  • Series circuits: I = same, V = adds up
  • Parallel circuits: I = adds up, V = same
40
Q

Efficiency:

A
  • Efficiency is a measure of how much useful energy an electrical device produces compared with the amount of energy that was supplied to the device.
  • Not ALL electrical devices use electrical energy efficiently.
41
Q

Efficiency in the real world:

A
  • 600 kW.h of energy is used by a computer if left on and not in use. If it is in sleep mode, it reduces to 20 kW.h. Notebook computers use less energy than regular computers.
  • Incandescent light bulbs use electrical energy to heat a wire, called a filament inside the glass bulb. The heated filament produces bright light but also produces thermal energy. It converts 10% of the electrical energy into light. Ontario wants to ban them by 2012.
  • Compact fluorescent bulbs are dangerous as they contain mercury.
  • The most efficient and safe type of bulb is the LED. They are already in use within christmas lights, computers, traffic lights, billboards, cars, and home gaming systems.
  • The EnerGuide and EnergyStar labels provide an estimate of how much electrical energy the appliance will use in one year.
42
Q

Calculating the efficiency of an electrical device:
Equation

A

%Eff = Eout/Ein x 100; in + out is measured in joules - Practice on pg. 78 + WB & TB
- Ein = P x t (power x time) - reference q. 4 - the cost of electricity in our homes

43
Q

Cost of Electricity:
Equation

A

Cost to operate (CT) = Power (P - kW/1000 - W) x time (t - hrs) x cost (cents)

44
Q

Conversions:

A

1000 MA = 1 A (divided by 1000), 1kV = 1000V (multiply by 1000)

Gr.9 (3 decks)

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