Chapter 4 Electricity heating and magnetic effect II Summary II Notes II Class 8 II Curiosity Book II Latest CBSE Notes

on

 

Ch: 4 Electricity heating and magnetic effect

Magnetic Effect of Electric Current

  • The production of a magnetic field around a current-carrying conductor is called the magnetic effect of electric current.
  • Electric current flowing through a wire produces a magnetic field. Magnetic field exists only while current flows.
  • The region around a magnet or a current-carrying conductor(wire) where magnetic force can be experienced is called a magnetic field.
  • This was first discovered by Hans Christian Oersted in 1820.
  • Applications include electromagnets, electric bells, motors, fans, and loudspeakers.

Current flowsà Magnetic field producedàCompass needle deflectsàCurrent stopsàMagnetic field disappearsàCompass returns to normal

How to create a Electromagnet?

·       Electromagnets are created by passing current through a coil; inserting an iron core strengthens them.

·       Electromagnets have two poles (North and South), and their strength depends on current and number of turns in the coil.

·       Polarity can be reversed by changing current direction.

·       Lifting electromagnets are used in factories and scrap yards to move heavy metal objects.

·       Electric currentàCurrent flows through coilàMagnetic field producedàIron core becomes magnetàElectromagnet formed

·       Earth behaves like a giant magnet because movement of molten iron inside Earth's core produces electric currents, creating Earth's magnetic field.

 Heating Effect of Electric Current

·       When electric current passes through a conductor, the flow of electric current causes the wire to heat up. This is called the heating effect of electric current.

·       Electric current flowsà Conductor offers resistance or stops current àElectrical energy changes into heat energyàWire becomes hot

·       Resistance is the property of a conductor that opposes the flow of electric current.

·       Nichrome wire is commonly used in heating devices because it offers high resistance.

·       Household appliances like heaters, stoves, kettles, irons, immersion rods, and hair dryers work on this principle.

·       Heat generated depends on wire material, thickness, length, and current strength.

Cells and Batteries

Inside every cell, chemicals react with each other. These chemical reactions convert Chemical Energy to Electrical Energy. This electrical energy makes electric current flow in a circuit.

An electrolyte is a liquid that allows electric current to pass through it because it contains dissolved ions.

Voltaic cell: It generates electricity through chemical reactions between two metals and an electrolyte.

 

Dry cells: It is widely used, with zinc as the negative terminal and carbon rod as the positive terminal.

Rechargeable batteries: can be reused multiple times (e.g., lithium-ion batteries in phones, laptops, vehicles).

Battery recycling is important to protect the environment and recover valuable materials.

Comments

Post a Comment