Electricity And Magnetism

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Electricity And Magnetism

• Laws of magnetism
• Electromagnetism
• Electric bell
• Electric charges and current
• Source of electricity
• Electric circuits
• Resistance

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INTRODUCTION

• Magnet is an object which attracts objects made
  up of iron, steel, nickel and cobalt.
• The property of magnet to attract such objects -
  Magnetism

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Magnetic Materials

•  Materials which are attracted towards a magnet
  are called magnetic materials.
• For e.g. iron, nickel and cobalt.

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NON- MAGNETIC MATERIALS

• Materials which are not attracted towards a
  magnet are called non-magnetic materials.
• For e.g. aluminium, zinc, wood, rubber, etc.

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Laws of Magnetism

• Attractive property of magnets
• Like poles repel and Unlike poles- attract
• Directive property freely suspended magnets
  always rest in the N-S direction
• Poles of a magnet cannot exist independently,
  they always occur together.

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Test for a magnet

• To prove Repulsion is surest test of magnetism
• From activity given material is magnet or not
• If not attracted then non- magnetic
• If repels then its a magnet
• If attracted then magnetic material or magnet
• If attracts then magnetic material
• If repels then magnet

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Electromagnetism

• When current passes through coil ( insulated wire
  wound around soft iron core), core behaves like
  magnet. This phenomena electromagnetism

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Electromagnetism

• Electromagnet is temporary magnet as its magnetic
  behaviour lasts for a long as current flows
• If material like steel or alloys are placed in
  coil and strong current pass through the coil (
  permanent magnet)

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Applications

• Electric motors, electric bell, electronic
  switches
• For lifting heavy load of iron, vehicles and
  scrap
• Mining industries to separate iron ores
• Deflects beam of electrons in Tv

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Electric Charges

• Atom- objects made up of tiny particles
• Every atom consists of 2 types of charges
  particles Protons() and Electrons(-)
• Under normal circumstances, amount of ve charges
  and ve charges
• of an atom are equal.
• The equal and opposite charges
• cancel each other and atom
• remains electrically neutral.

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Electric Charges

• When these charges stay on an object Static
  electricity
• Moving charges Electric current or Simple
  Electricity
• The SI unit of electrical charges
• is coulomb (C)

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Electric Current

• Atoms of metals contains very loosely bound vely
  charged electrons in their outermost orbits.
• These electrons are free electrons which moves
  randomly in all directions in a material
• When free electrons are made to flow in
  particular direction electric current

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Electric Current

• An electric current (I) the amount of charge
  (Q) flows through a point in unit time(t).
• ?? ?? ?? coulombs / second
• SI unit of current (I) is ampere (A).
• 1 A 1 coulomb / 1 second

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Sources of electricity

• Different sources of electricity
• are cells, batteries, solar cells,
• power plants, generators and so on
• Electric Cells
• Produce by converting chemical
• energy into electrical energy
• 2 types Primary and Secondary

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Primary Cells

• Cells that can be used only once
• When chemicals are used up completely, the cell
  becomes dead and cannot be used.
• Most commonly primary cell is dry cell . The
  chemicals in them are in form of thick paste
• Primary cells like voltaic cell, Daniel cell,
  Leclanche cell contains chemicals in liquid form

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Primary Cells
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Dry Cells
Plaster of Paris
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Dry Cells Applications

• Available in different sizes and powers to suit
  different requirements
• Unlike liquid cells, they can be fitted inside a
  device without any risk
• Easy and safe for transportation

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Batteries

• The amt of current produced by cells is very
  small
• So, 2 or more cells are combined together to give
  larger amt of current for practical purposes
• A combination of more than one electric cell to
  produce a larger amt of current - Battery

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Secondary Cells

• Recharged by passing current through them
• Reverse reaction takes place inside the cells and
  original chemicals are restored
• used again and again after recharging
• Storage cells/ Accumulators
• 2 types

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Lead-Acid Battery

• Used in vehicles and inverters
• Consists of several secondary cells connected
  together
• Each cell has plate of lead and lead oxide dipped
  in an acid solution

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Dry Batteries

• Used in cell phones, electronic cameras and other
  portable devices

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ELECTRIC CIRCUIT

• An electric circuit is a path along which
  electricity can flow.
• Circuit consists of source of current, device,
  switch, wires
• The wire and bulb form a continuous path between
  two terminals of the cell for electricity to flow
  through. This path is called an electric circuit.

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ELECTRIC CIRCUIT

• The arrangement of electric components is
  generally shown by symbols Circuit Diagram
• The flow of E.C. in any circuit is from ve
  terminal to ve terminal.

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ELECTRIC CIRCUIT

• Each component of a circuit is represented by a
  unique symbol.

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Closed And Open CIRCUIT

• The electric circuit in which there is a gap in
  the connections between the terminals of the
  cell, wires and the bulb etc. An Open Circuit
  Or Incomplete Circuit
• The electric circuit in which there is no gap in
  the connections between the terminals of the
  cell, wires, bulb etc. Complete Circuit Or
  Closed Circuit.

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Series Circuit

• In a series circuit, each device is connected in
  such a manner that there is only one path through
  which current can flow.

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Series Circuit

• All device work Switch ON
• If any device is out of order , stop working
• Same current flows through all devices, if any
  device is not working then it result in open
  circuit or not work.

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Parallel Circuit

• In parallel circuit, all the electrical devices
  are connected by means of parallel connections
• There are multiple paths through which current
  can flow in parallel circuit.

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Parallel Circuit

• Devices can function independently
• If any device out of order still works
• Each gets enough energy so it works with full
  capacity.
• Advantages houses, factories, offices

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Electrical Resistance

• When the electrons move from one part to other
  part, they collide with each other and the walls
  of the materials which acts as Obstacles
• This obstacles is nothing but Resistance
• These collisions tend to slow down the flow of
  electrons and hence oppose the flow of electric
  current through the material
• The property of a material due to which it
  opposes the flow of current through it
  Resistance

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Conductor, Insulator

• Conductor Allow current
• Metals, Impure water, Salt Solution
• Materials offer Low resistance
• Insulator doesnt allow current
• Wood, rubber, plastic
• Materials offer high resistance

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Resistor

• A resistor is an electrical component that limits
  or regulates the flow of electrical current in an
  electronic circuit.
• Tungsten, constantan, nichrome are resistors
  used in heaters, toasters, electric iron etc.

Resistor Device used to reduce current flow.
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