science electricity topics 4 and 5

How long will a fuel cell continue to produce electricity

A fuel cell will continue to supply electricity if fuel is still being supplied. It lasts up to 5000 to 10 000 hours.

difference between primary and secondary cells

A primary cell cannot be recharged but a secondary cell can. In a primary cell the chemical reaction is irreversible but in a secondary cell it is reversible

What are the main components in a voltaic cell

Anode - electrode where oxidation occurs Cathode - electrode where reduction occurs Salt bridge - chamber of electrolytes necessary to complete the circuit in a voltaic cell Half cells - is where the oxidation and reduction reactions are separated into compartments External circuit - used to conduct the flow of electrons between the electrodes of the voltaic cell and usually includes the load Load - part of the circuit which utilizes the flow of electrons to perform some function

What would happen if an electric current was passed through a piezo-electric crystal

If a piezo-electric crystal were to generate an electric charge that would mean it was either compressed or stuck. If an electric current was run through this crystal its shape would change slightly. This makes them useful in many ways

electricity to light

In incandescent light bulbs, a filament made of a high-resistance metal glows brightly when an electric current passes through it In fluorescent or neon bulbs, the electric current causes a gas or vapour to glow brightly Piezoelectric crystals can produce light when they are hit together

three ways in which usable light can be produced from electricity

Incandescent lights - works by passing electricity through a wire filament, until it gets so hot that it glows. The filament is protected by glass or quartz. Fluorescent lights - electric current is passed through these tubes, which contain gases like mercury vapor. This produces a shortwave ultraviolet light. This light causes a phosphorus coating on the tube to glow. LED lights - contain semiconductor materials that are used as a light source. When a voltage is applied, the movement of electrons produces light. This process is called electroluminescence.

What was Luigi Galvani's discovery

Noticed that a frog's muscle would twitch when touched by two different metals. Believed that the frog's tissues had a unique ability to generate "animal electricity"

How is electricity created in a fuel cell

Passes hydrogen through the anode and oxygen through the cathode of a fuel cell. At the anode, the hydrogen molecules are split into electrons and protons. The protons then are passed through the electrolyte membrane and the electrons are forced through a circuit, generating an electric current.

a device, usually composed of silicon, that can be used to produce electricity from light

Photovoltaic cell

a push-button barbeque lighter produces a small electric current

Piezoelectric device

What was it called

Seebeck Effect

What was Alessandro Volta's discovery

Showed that a voltage could be generated without using living tissue by placing different metals in a solution containing salt or acid

How does LED work

Solid state electronic components that glow when electricity flows through them. Use a fraction of the power of a traditional bulb and last for years. The heart of a LED is a tiny semiconductor chip that is often protected by a transparent plastic case. Only work when connected to a circuit in one direction

cells

The chemical reaction in a cell determines the potential difference (voltage) that the cell can create To obtain higher voltages, batteries contain several cells connected in series If a cell cannot be recharged (a primary cell), the amount of chemicals it contains determines the total amount of electric energy the cell can produce Rechargeable secondary cells use chemical reactions that can be reversed In a recharger, electricity is forced through the "dead" cell, rebuilding the original chemicals and allowing the cell to be reused

Thermo-electric generator

plants that burn fossil fuels to generate electricity based on thermocouple

potential energy

stored energy

mechanical energy

the energy associated with the motion and position of everyday objects

a form of energy that is always transferred from a warmer substance to a cooler one

thermal energy

device that converts heat to a small amount of electric energy often used in temperature sensors.

thermocouple

Thermopile

thermocouples connected in series Heat from a gas burner or another heat source moves through several thermocouples connected in series creates a potential difference extremely reliable, low-maintenance devices They are used in remote locations to generate limited quantities of electrical energy that are sufficient to power, for example, emergency communications equipment

thermocouples combined to produce greater amounts of electricity

thermopile

whats in a electrochemical cell

two metal electrodes are surrounded by an electrolyte, a substance that can conduct electricity

Motion to electricity

A barbecue "spark" lighter uses the piezoelectric effect in reverse While a piezoelectric crystal is being compressed or pulled, a potential difference builds up on opposite sides of the crystal Conductors attached to the crystal can connect it to a circuit, where the crystal acts as a source of electric energy In a barbecue lighter, this creates a spark

A single cell can usually create 1.5V, yet some batteries can create 6V or 9V

Batteries are made up of various cells increasing the voltage difference between a single cell and a battery because the number of cells in a battery all contribute to the final amount of voltage a battery contains so a single cell cannot compare to the amount of voltage in a battery because a battery does not have a single cell determining its voltage

In what way are fuel cells environmentally friendly?

Clean, have no combustion/emissions, reduce carbon dioxide, no pollutants emitted

photovoltaic cell

Convert light energy from the sun into electrical energy Made of a miconductor material such as silicon When light strikes the cell, some light is absorbed by the semiconductor material, breaking electrons loose and allowing them to flow freely eg - calculators,water heaters, or emergency roadside telephones N type doping = excess of electrons P type doping = excess of holes P type and n type semiconductors have a pn junction in between them Electrons diffuse across the pn junction from the n type material to the p type material creating positive charges in the n type material Holes diffuse across the pn junction creating negative charges in the p type material Area near pn junction = depletion zone where there are no charge carriers present Separated positive and negative charges create an electric field across the depletion zone When light is absorbed by the semiconductor, extra free electrons and holes are created Electric field makes the electrons flow to the n type material and holes flow to the p type material Separation of charges creates a potential difference across the pn junction Electrons flow through an external wire to the p type material to unite with the holes, producing an electric current

What two other devices use a piezoelectric crystal

Crystal microphones Pressure sensors

electrical energy

Energy caused by the movement of electrons.

light energy

Energy in the form of moving waves of light

What did Joseph Bar-Cohen create

He created a robotic hand with four "fingers". When voltage is applied, teh plastic "fingers" bend, gripping any small object between them

thermal energy

Heat energy

What does the acronym "LED" stand for

Light emitting diodes

electricity to motion

Piezoelectric effect Sound is produced when an electrical current causes vibrations in a tiny crystal Piezo in Greek means pressure or push When a piezoelectric crystal such as quartz or Rochelle salt is connected to a potential difference, the crystal expands or contracts slightly ny material touching the crystal experiences pressure which can create sound waves or vibrations

Why are thermo-electric generators most often used in remote locations

Relatively immune to nuclear radiation and because and last for a long period of time and are mostly maintenance free

How do batteries differ from cells? What arrangement of three cells will result in the greatest electric current? Which arrangement would result in the greatest longevity for the battery?

The difference between batteries and cells is that batteries are a collection of cells while cells are a single unit converting chemical energy into electrical energy. The arrangement that will result in the greatest electric current will be a series circuit. The arrangement that will result in the greatest longevity for the battery will be a parallel circuit because then the batteries will not be giving off all their power at the same time like a series circuit would.

D, C, AA or AAA.

The letters on batteries give the size, in height and width of the battery.

when was the link between electricity and pressure investigated

The link between electricity and pressure was first investigated in 1880 by two young French scientists: pierre and jacques curie

What is the definition of heat

Thermal energy transferred from one object to another because of temperature difference

an advantage of thermocouples over regular liquid thermometers

Thermocouples are useful over a wide temperature range, fast response time, durable, low cost

Who discovered the basic principle of the thermocouple

Thomas Johann Seebeck in 1812

What are the by-products of the fuel cell's reaction?

Water, electricity, and heat.

What happens to a piezoelectric crystal when it is squeezed

When you squeeze certain crystals such as a quartz you can cause electricity to flow through them and a potential difference builds up on opposite sides of the crystal. It will deform the structure and the atoms will either be pushed together or farther apart.

Thermocouple

a device that converts thermal energy into electrical energy without moving parts a loop of two wires made of different types of metals. The wires are wrapped together at both ends or junctions When one junction is heated, a small electric current is produced If the temperature difference between the junctions is increased, the current increases. For example, one junction might be cooled while the other is heated. If the positions of the hot and cold junctions are reversed, the current will flow in the opposite direction device used for measuring temperatures

dry cells

an electrochemical cell in which the electrolyte is a paste (regular batteries) have a paste, plastic, or ceramic solid electrolyte the electrolyte is restrained by either a porous container or mixing with a gel medium. lighter and compact

how can heat be converted directly into electrical energy

by using a thermocouple

What are the two most common combinations of metals used in industrial thermocouples

copper + constantan and iron + constantan

different types of metals in a voltaic cell that have different attractions for electrons

electrodes

a substance that can conduct an electric current through the movement of ions

electrolyte

sound energy

energy carried by sound waves

kinetic energy

energy due to motion

wet cells

have liquid electrolytes Car batteries contain several wet cells Aluminum-copper is a typical wet cell Some moist cells are usually recharges while others are only superior for a short time There are many different types of wet cell batteries categorized at main or secondary Main - a major battery can be used only right up until ist substances are fatigued or cannot react with each other anymore Secondary - can be recharged by properly reversing the inner chemical course of action used to deliver a charge have a fluid, and the fluid is free to move heavier and bulky