• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Conductors and Insulators.

Extracts from this document...

Introduction

Conductors and Insulators

Not all substances are good conductors of electricity. As a general rule, metals are good conductors whereas non metals are poor conductors. The poorest of conductors are commonly called "insulators," or "non conductors." Aluminium, copper, gold, iron, mercury, nickel, platinum, and silver are examples of good conductors. Amber, glass, mica, paper, porcelain, rubber, silk, and sulphur are all non conductors. The difference between a conductor and an insulator is that in a conductor, there are free electrons, whereas in an insulator, all of the electrons are tightly bound to their respective atoms. In an uncharged body, there are an equal number of positive and negative charges. In metals, a few of the electrons are free to move from atom to atom, so that when a negatively charged rod is brought to the end of the conductor, it repels nearby free electrons in the conductor, causing them to move. They in turn repel free electrons in front of them, giving rise to a flow of electrons all along the conductor.

Direct current

Direct current (DC) is the continuous flow of electricity through a conductor such as a wire from high to low potential. In direct current, the electric charges flow always in the same direction, which distinguishes it from alternating current (AC). DC is commonly found in many low-voltage applications, especially where these are powered by batteries, which can only produce DC.

...read more.

Middle

The constant R is the resistane of the conductor and the equation is knowen a OHMS law. We can also say that the P.D. across the conductor is directly proporional to the current flowing through it at constant temperature. The equation can be rearranged as:

                                R = V                                                                                        I                                                      Where V is the P.D. across the conductor and I is the current through it . From this equation it is clar that:                1Ω = 1V                                                                                          1A

Alternating current

Electrical AC (alternating current) occurs when charge carriers in a conductor or semiconductor periodically reverse their direction of movement.  Household utility current in most countries is AC with a frequency of 60 Hz (60 complete cycles per second), although in some countries it is 50 Hz. Some AC waveforms are irregular or complicated. An Irregular AC wave is produced by audio amplifiers that deal with analogue voice signals and/or music. The voltage of an AC power source can be easily changed by means of a power transformer. This allows the voltage to be stepped up (increased) for transmission and distribution.  High-voltage transmission is more efficient than low-voltage transmission over long distances, because the loss caused by conductor resistance decreases as the voltage increases. D.C current is different to A.C because it does not reverse direction of movement it continues one way, D.C is now not used as widely as A.C and most appliances that use D.

...read more.

Conclusion

blood circulation in a limb or your heart, and your doctor has requested a Doppler ultrasound to look at the blood flow. Ultrasound has been a popular medical imaging technique for many years.Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the technique used by bats, whales and dolphins, as well as SONAR used by submarines. In ultrasound, the following events happen:
  1. The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe.
  2. The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).
  3. Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected.
  4. The reflected waves are picked up by the probe and relayed to the machine.
  5. The machine calculates the distance from the probe to the tissue or organ using the speed of sound in tissue and the time of the each echo's return (usually on the order of millionths of a second).
  6. The machine displays the distances and intensities of the echoes on the screen.

image04.jpg

This is a picture of the order of how a ultrasound works.

Biliography

GCSE Physics book

www.explorescience.com

Advanced physics textbook

Physics for you text book

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Electricity and Magnetism essays

  1. Marked by a teacher

    Thermal insulators.

    4 star(s)

    Start volume Start volume Room Temp Room Temp Material (insulator) Surface area of beaker Surface area of beaker * * this is a variable because it changes the amount of convection that happens. Method 1. Prepare the beakers by insulating them with the five materials (except the control)

  2. Marked by a teacher

    In this coursework, I will be analyzing and proving that although metallic conductors are ...

    3 star(s)

    These electrons move randomly and haphazardly, thus, for e.g., in a copper atom, for every 5 electrons moving left, there are 5 electrons moving right, so the potential difference is nullified. And for a current to be present, there has to be a potential difference.

  1. Electromagnetism - investigating what effect increasing the number of turns in a coil on ...

    This is because; as we can see from out pretest that it is the lowest amount of turns which will holds a steady amount. I did not want to start at 10 turns, as it is unpredictable that the coil would have any affect on the soft iron core and I would definitely get a result.

  2. Choosing a light source

    * Distance between the slits on the diffraction grating. This depends on the grating that is used. * The angle at which the telescope is placed for the grating. This is found by looking a the venire scale. * Order of the angular separation of the interference fringes.

  1. Investigate various materials to see if they are good or bad insulators.

    In my past knowledge and experience I know that material can be effected by three main causes -Conduction In conduction the particles vibrate slowly at first, as they absorb heat energy they vibrate faster. They pass the vibration to the adjoining particle.

  2. Some materials are better insulators than others. Investigate various materials and discuss thier relative ...

    They pass the vibration to the adjoining particle. The energy (heat) is transferring along the metal rod. Conduction can only occur in solids as the particles are too far apart. Conduction is the flow of the heat through matter of places of higher temperature places of lower temperature without movement of the matter as a whole.

  1. "Are rechargeable batteries more economical than alkaline batteries?"

    of the voltmeter used during the experiment may have affected the result. P.T.O Modern Battery / Dry Cell Fig 46. Cutaway view of an alkaline battery. Figure 4. shows the new modern battery found in the supermarket nowadays. This type of cell is still based on the wet/ galvanic cell

  2. Aseptic technique

    The goggles can also protect the eye from objects being hurled across the laboratory by immature minds or by the smashing of glass which would send pieces flying in all directions. In the case that somebody's eye/eyes came in to contact with chemicals follow through the procedures of emergency eye

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work