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Science 9 Electrical principles and technology
Transcript of Science 9 Electrical principles and technology
Invented by Nikola Tesla over 100 years ago.
It can generate large amounts of electricity, enough to be lethal to humans.
Used as special effects apparatus in movies, and also for studying high voltage in laboratories.
The crackling arcs of electricity are caused by electricity jumping from one metal rod to another.
The arcs travel upwards because the electricity heats the air it passes through and, as this hotter air rises, it carries the spark upwards.
Use the following questions to understand how to transfer, modify, measure, transform, and control electrical energy:
How do we obtain and use electrical energy?
What scientific principles are involved in developing, selecting, and using energy-consuming devices?
How can the principles of electricity be applied in technology to promote efficient and effective energy use?
Grade 9 Unit D
Electrical Principles and Technologies
Distinguish between static and current electricity and identify evidence of each
Assess the potential danger of an electrical device by checking its voltage and amperage
Distinguish between safe and unsafe activities when dealing with electricity
Identify electrical conductors and insulators
Evaluate the use of different chemicals, chemical concentrations, and designs for electrical storage cells
Electric charge and current
Electrical energy storage
Measures and units of electrical energy
Static Electricity: a stationary electrical charge.
Static electricity causes:
Shocks from touching doorknobs
Clothes to cling together
1.1 Static Electricity
Remember that some subatomic particles are electrically charged:
Proton: positively charged particle
in the nucleus of the atom.
Electron: invisible negatively charged particle
that orbits the nucleus of the atom.
Neutron: neutral particle in the nucleus of an atom
*These charges can either attract or repel other particles.
Neutral: description of an object that
has equal amounts of positive and
An object is said to be electrically charged if there is more of one type of charge than another.
For example, dragging your feet along the carpet transfers electrons from you to the carpet. This would result in you having more protons than electrons, for a net positive charge.
With electrically charged particles
When an object builds up more of one type of charge than another it is said to be statically charged.
Static means stationary or not moving.
This type of charge does not flow (continuously) but may discharge when given the opportunity.
Neutral objects are attracted to charged objects due to charge separation.
Charge Separation: concentration of like charges in specific areas of a neutral object, caused by the approach of a charged object; for example, a negatively charged object brought close to a wall repels the electrons in the wall, leaving the area of the wall closest to the object positively charged.
Electrical Discharge: sudden transfer of electrical charge from one object to another, indicated by a spark.
Built up static charges, in one object, that are attracted to another object may “jump” to that object.
The behaviour of electrical charges can be summarized in two laws:
The Laws of Electrical Charges:
Opposite charges attract each other.
Like charges repel each other.
Van de Graaff Generators (VDG)
are used to study electrical discharges.
They are very effective at building up static charge.
VDG’s use friction to build up static charge.
How a VDG works:
A rubber belt rubs against a piece of metal (source of electrical charge)
The metal sheds electrons to the belt.
The belt transfers these electrons to the metal sphere
The charge builds up on the sphere until it is statically discharged.
While like charges repel