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Science Electricity Review Cheat Sheet by

Grade 9 Electricity Review
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Static Electr­icity

Static Electr­icity:
Produces 'Static Charges', meaning that the charge(s) are stationary on the surface of the object that was rubbed.If the object gains electrons, it has negative charge.Loses electrons, positive charge.To charge, must rub an object that takes electrons w/ one that gives electrons.

Different Ways of Charging

Different Ways of Charging:
• Induction, without direct contact
• Friction, rubbing 2 different insulators together
• Conduc­tion, touching a charged insulator to a conductor

Conductors and Insulators

Conductors are a group of materials that allow for electrons to pass through them easily.There are two types, good conductors (metals) and fair conductors (allow for passage just not as much as fair conduc­tor­s).I­ns­ulators are materials where electrons can't move easily through them.

Primar­y/S­eco­ndary Cells

Primary cells can only be used once and secondary cells can be recharged and reused over and over again.

Efficency

Is the measure of how much useful energy the electrical device produced over the amount it has used.You would measure this by using the formula
Eout(e­nergy out, produced energy­)/E­in(­Energy in, the amount of energy being used)x­100%.

Series and Parallel Circuits

Series Circuits have only one path for the electrons to follow and Parallel Circuits have more than one.The more loads you add to series circuit, the more resistance you will have and the less current you will have.Also, if you increase the number of loads in a series circuit, the voltage drop across each circuit decrea­ses.The current flowing through a load in a parallel circuit is less than the current flowing through the energy source.The resistance in a parallel circuit is only the load resist­anc­e.The voltage drop of a load in a parallel circuit will be the same as the drop across the source.

Potential Difference

This is also called voltag­e.P­ote­ntial Difference is the difference in electrical potential energy per unit at two different points in the circui­t.The device used to measure this is the voltmeter, the unit is the volt and the symbol is V.You can only measure this by placing the voltmeter parallel to a load.

Ohm's Law

 
Resistance
Electrical Current
Potential Difference
Measures
Opposition to Flow
Electron Flow
Force
Symbol
R
I
V
Measure in
Ohms (Greek Delta)
Ahms(A)
Volts(V)
Device
Ohmmeter
Ahmmeter
Voltmeter
Formula
R= V over I
I = V over R
V=I x R

Circuit Symbols

 

Electr­ostatic Series

Electr­ostatic Series:
It determines whether or not the substance has
a strong or weak hold on electrons.

The Law of Attraction

The Law of Attrac­tion:
If the two objects have like charges (ex positive, positive), they repel.
If they have unlike terms (ex positive, negative), they attract.

Charging by Conduction

Occurs when two objects with different amounts of electric charge come in contact with one another and the electrons move from one another.It does not always have to be between a charged object and a neutral one.The electrons always move from the object w/ more electrons to the one w/ less.

Electric Discharge

This occurs when 2 objects that have a charge imbalance are brought close together or come in contac­t.The greater the imbalance, the greater the discharge will be.Small discharges cause shocks and big discharges can damage electronic equipment.

Electrical Power

Is the rate at which electrical energy is used/p­roduced in a given time.This is measured in watts(w).1 watt=1 joule per second (J/s).The higher the wattage, the more energy is being used/p­rod­uced.

Power

P(Watt­s)=­Energy divided by delta T(Time­(se­conds)

P=Voltage x I(Current)

Measuring Electrical Energy

Measure by formula
Energy­(Jo­ule­s)=­Voltage Drop (V) x Current (A) x Time Interval (s)

OR

Energy (Watt Hours (Wh))=­Voltage Drop (V) x Current (A) x Time Interval (h)

Resistance

This is the ability of a material to resist the flow of electr­ons­(cu­rre­nt).In­sul­ators tend to have a high resist­ance, conductors a low resist­anc­e.The device used to measure this is the Ohmmeter, the unit is the ohm and the symbol is the Greek Omega.The greater the resist­ance, the lower the current and vice versa.A Resistor is a device put in the circuit to limit the curren­t.When using a graph, the slope is the resist­anc­e(find by using rise over run)

Electr­ostatic Series Diagram

 

Charging by Friction

Always one material will lose electrons and the other will gain.U­sually occurs when you rub two objects togeth­er.U­sing the electr­ostatic series, you can determine which material will lose/gain electrons.

Weather

Static electr­icity is more common in colder weather as the cold air is drier.The more humid the air is, the harder it is for the object to maintain a charge.

Grounding

Excess charges can be removed from an object through ground­ing.This process is used by removing the excess charge to a large neutral object­(mostly the Earth).The electrons move to the Earth if the object is negatively charged, from the Earth if it is positively charged.

Induction

Induction is where a charged object is used to charge a neutral object without contact.It can be charged both perman­ently and tempor­arily.

Temporary Charge:
When the charged object is brought close to the neutral object, the electrons in the neutral object are forced to shift in positi­on.If the charged object is charged negati­vely, the electrons will move away and the object will be tempor­arily charged positi­vel­y.Vice versa for a negative object.Once the object is taken away, the electrons return to normal.

Permanent Charge:
The neutral object can be charged by grounding it when you bring the charged object close to it.The object that was originally charged will keep it's charge where the neutral object will be the opposite charge.

Direct­/Al­ter­nating Current

Direct current is when the electrons only flow in one direction and it's produced by an electric cell.A­lte­rnating current is where the electrons move back and forth, altern­ating direct­ion­s.This type can only be produced by genera­tors.

Cost of Electr­icity

Measure by the formula:
power used x time x cost of electr­icity

Static Electr­icity Diagram

Induction Permanent Charge Diagram

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Comments

DaveChild DaveChild, 09:01 15 Apr 14

There was an issue with gif images on the PDFs, which I've now resolved. The new PDF is now being created properly for this cheat sheet.

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