Electricity - Study Notes

Electricity: A form of energy that results in the interaction of charged particles such as electrons or protons.


Static Charge: An electric charge that tends to stay on the surface of an object, rather than flowing away quickly.


In order to double the current you must

Double the Voltage and the Resistance Stays the same

Decrease the Resistance keep the Voltage the same


Voltaic Cell: A source of energy that generates an electric current involving 2 different metals and a solution that is a conductor.


Dry Cell: a cell that contains an electrolyte that is paste


Wet cell: a cell that contains an electrolyte that is a liquid


Primary Cell: A cell that can only be used once


Secondary Cell: A cell that can be used more than once.


Battery: A connection of 2 or more cells


Electrolyte: A solution or paste that conducts charge.


Solar Cell: A Cell that converts sunlight into electrical energy.


Charging By Friction


Objects made from different materials rub against each other, producing a net static charge on each.


Both objects become oppositely charged.


Objects at the top of the electrostatic series have a weaker hold on electrons that objects at the bottom who have a stronger hold.


Electrostatic Series: A list of materials that have been arranged according to their ability to hold on to electrons.


Anti static sheets work by having a waxy layer and the heat evaporates it onto all the clothes. This makes the clothes act as if they are all the same material.

Charging by Induction


When a charged object is close to a neutral object, the electric field of the charged object produces a force on the neutral object.


Allows you to give an object a temporary charge by splitting them into 2 differently charged portions


If grounded charge will become permanent.


The movement of electrons in a substance caused by the electric field of a Induced Charge Separation: nearby charged object, without direct contact between the substance ant eh object.

Charging By Contact


The cause of Static Shocks


Occurs when 2 objects that have different charges touch each other and will transfer electrons to balance themselves evenly.


Example: If a positive rod is used to create a charge (By contact) on an object, there is a flow of electrons from the object to the rod. Because only electrons move and to balance the rod (Neutral) It needs electrons.


Insulator & Conductor


Insulator: A material in which electrons cannot move easily from one atom to another


Conductor: A material in which electrons can move easily between atoms


Semiconductor: A material in with electrons can move fairly well between atoms.

Laws of Electric Charges


Opposite charges Attract


Like Charges Repel


Positive and negative charges attract neutral objects




Ground: And object that can supply a very large number of electrons to, or can remove a very large electrons from, thus neutralizing the object.


Grounding: Removing charges from an object and returning it to a neutral state. AKA Discharging.



Storm clouds form when hot and cold air meet. Lightning strikes are negative charges in clouds are attracted to positive charges in the ground.


Lightning takes the easiest path therefore it strikes the highest object


Lightning rods are used to attract the lightning strike and they are grounded


Electroscope: A device used for detecting the presence of an electric charge.


Types of Circuit


Circuit: A closed path along which electrons that are powered by an energy source can flow.


Series Circuit: The components are connected end to end. One after an other. They make a simple loop for the current to flow. If any components blow the whole circuit will not work


Parallel Circuit: The components are side by side. This way the current is split to different paths to reach each component. This way if one component blows the other will stay.


Open Circuit: A Circuit with a gap or break.

Voltage (V)


The amount of energy each electron has within a circuit.


Measured in Volts (V)


Resistance (R)


Resistance is the inability of electricity to pass through a substance.


Measure in Ohms



A resistor or any device that transforms electrical energy into heat, Motion, Sound, or Light.



The resistance in wires depends on:


- The type of material


- The length


- The diameter (Bigger diameter, less resistance)


- The Temperature (Hotter wires have greater resistance)



Current (I)


Is the flow of electricity


Abbreviation  “I”


Measured in Amps “A”


1 Amp = 1 Coulomb


Solving Circuits



- IT= I1=I2

- VT= V1+V2

- RT= R1+R2



- IT= I1+I2

- VT=V1=V2

- 1/RT=1/R1+1/R2

- Voltage = Resistance X Current

- V=RI




E=Pt (Energy = Power X Time)


P=VI (Power = Voltage X Current)


V=RI (Voltage = Resistance X Current)




Efficiency = Output Energy/Input Energy