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• Matter comprises atoms that have electrons, protons, and neutrons, known as subatomic particles.
• Electrons and protons possess a property called electric charge that causes them to interact.
• Electricity is the movement of energy using moving charges from one location to another.

Types of electric charges

• Electric charges come in two forms: positive and negative.
• Protons have a positive charge, electrons have a negative charge, and neutrons are neutral.
• Protons and neutrons are located inside the nucleus and electrons orbit around it.
• In an atom, the number of protons equals the number of electrons.
• An atom is electrically neutral because the total positive charge equals the total negative charge.
• Coulomb (C) is the SI unit of electric charge, named after Charles Augustin de Coulomb.
• The elementary charge is the amount of charge on an electron or proton, denoted as 'e', equal to 1.6 × 10^-19 coulombs.
• Both electrons and protons have the elementary charge 'e', but electrons are negatively charged and protons are positively charged.
• A single electron or proton's charge is minimal; 6.25 × 10^18 electrons or protons are needed to create a 1 C charge.
• 1C equals to 6.25x10^18 electrons.
• Atoms can gain or lose electrons to become non-neutral.
  • Atoms that gain electrons become negatively charged anions.
  • Atoms that lose electrons become positively charged cations.
• Charged particles, or atoms with electric charge, are called ions.

Properties of Electric Charge

• Like charges repel, and opposite charges attract.
• The net charge on a body is the sum of all charges, considering their polarity.
• Charge on a body is always quantized, meaning it exists in integer multiples of the elementary charge 'e'.
• The formula for the charge on a body is Q = ±n × e, where 'n' is the number of elementary charge particles, 'e' is 1.6 × 10^-19 C and 'Q' is the net charge.
• Electric charge is a scalar quantity.
• Electric charge is always conserved.
• By gaining or losing electrons, neutral bodies can become negatively or positively charged, and this process of gaining or losing electrons is called charging a body.

Charging a Body by Friction

• Rubbing two bodies (at least one is a non-conductor) produces heat due to friction.
• This heat excites electrons in both bodies, and the body with greater electron affinity attracts electrons.
• Both bodies develop equal and opposite charges.
• The body gaining electrons becomes negatively charged, while the one losing electrons becomes positively charged.
• For example, combing dry hair causes the comb to become negatively charged and attract small pieces of neutral paper.
• Similarly, rubbing a balloon against dry hair makes it negatively charged and able to attract neutral or positively charged bodies.
• A charged body attracts a neutral body.

Conductors and Insulators

• Conductors allow charges to flow through them due to the presence of free electrons.
• Metals are generally good conductors, with gold being the best, followed by silver, copper, and aluminum.
• Graphite, electrolytic solutions (like aqueous solutions of NaCl, HCl, H₂SO₄), and tap water are also conductors.
• Insulators do not allow electric charges to flow because they lack of free electrons.
• Examples of insulators include rubber, glass, wood, plastics, porcelain, pure distilled water, sugar, and vacuum vacuum being the best insulator.
• Water with salt conducts electricity because there are free ions and distilled water does not.
• Cations are positive ions and anions are negative ions.
• Semiconductors have conductivity between conductors and insulators, for example, silicon and germanium.
• Increasing temperature can make semiconductors conductive.
• Semiconductors are used to create electronic circuits, such as computer chips.

Electric Current

• It is the flow of electric charges through a conductor or electrolyte.
• Electric current is the charge flowing through a point per unit time.
• If Q coulombs flow in t seconds, the current I is I = Q/t.
• The unit of electric current is coulomb/second, also known as ampere (A).

Electric Cell

• It provides electricity on a small scale for devices like remote controls and watches.
• An electric cell converts chemical energy into electrical energy.
• An electric cell has two terminals (+ and -), that when connected with a wire or a device like bulb, current flows from the + to the - terminal.
• A battery is a combination of multiple electric cells.

Direction of Electric Current

• Initially, electric current was thought to be the flow of positive charges, moving from the positive to the negative terminal of a cell known as conventional current.
• JJ Thompson later discovered that electrons are the particles that flow, however current is carried by positive and negative ions in electrolytes.

Flow of Electric Current in a Wire

• Electric current is the flow of electrons in a metal wire when a cell or battery is applied.
• A conductor has free electrons that move randomly.
• Connecting a cell or battery to the conductor sets the electrons in motion from the negative to the positive end.
• These moving electrons is what constitutes electric current.

Electric Circuit

• A continuous conducting path where electric current can flow.
• It consists of devices like a bulb, switch, resistors connected through conducting wires to a source.
• There are two types of circuits:
  • Closed Circuit: A continuous conducting path that allows current to flow.
  • Open Circuit: A non-continuous path that doesn't allow current to flow.

Electrical Conductivity

• It measures the ability of a substance to carry electric current.
• Good conductors have high conductivity, whereas poor conductors like insulators have low conductivity.
• Pure water is a poor conductor without free ions.
• Water with salts conducts electricity due to the presence of free ions.
• Even small impurities in water can make it conductive.

Electrolysis

• It is the process where a chemical compound's solution conducts electricity and undergoes a chemical change.
• Some associated terms are:
  • Electrolyte: A solution of a chemical compound that conducts electric current and undergoes a chemical change.
  • Non-electrolyte: A solution that doesn't conduct current and undergoes no chemical change.
  • Electrodes: Conductors through which current enters or leaves an electrolytic solution.
  • Cathode: The electrode connected to the negative terminal.
  • Anode: The electrode connected to the positive terminal
  • Ions: Electrically charged atoms or groups of atoms formed when a chemical compound dissolves in water.
  • Cations: Positively charged ions formed, are discharged at the cathode during electrolysis.
  • Anions: Negatively charged ions formed, are discharged at the anode during electrolysis.
  • Voltmeter: The device used to carry out electrolysis, contains a vessel, two electrodes and electrolyte.
• Adding sulfuric acid to water during electrolysis increases conductivity by increasing free ions. Bubbles or metal deposits may form on electrodes, and the solution color may change.
• The chemical reaction in water electrolysis is 2H₂O →2H₂ + O₂.

Electroplating

• Electroplating is a common electrolysis application used to coat metals with others for example silver and gold.
• Electroplating is the process of depositing a thin layer of a metal over a conductive surface.
• The material to be electroplated is the cathode, and a coating material is the anode.
• When current is applied through circuit reactions take place using a soluble salt made of the anode's material.
• At the anode, metal atoms undergo oxidation and become metal ions.
• Reduction of ions that exist, results in atoms getting deposited on the cathode.

Uses of Electrolysis

• Electroplating coats wheel covers, handles of bicycles, and jewelry with nickel, chromium, silver, or gold.
• Galvanization uses a protective coating of zinc on iron, copper, or steel to prevent rusting.
• Electrolysis is used to obtain pure metals.
• It is also used to extract metals from their ores.

Safety Measures While Using Electricity

• Electric shocks can damage cells and cause heart attacks or death.
• Precautions include: using good quality wires with proper insulation, replacing defective plugs/sockets/wires/switches immediately and not touching switches/plugs with wet hands.
• In case of fire occurs, switch off the main.
• Appliances should be properly grounded.
• Wear rubber-soled shoes during electrical repairs.
• Avoid touching inside a socket.