Class 8 Science - HARYANA
Electricity: Magnetic and Heating Effects
This chapter explores the fascinating transformation of electrical energy into other forms of energy, specifically heat and magnetism. Students learn about the heating effect of electric current, which is used in everyday appliances like electric irons, heaters, and fuses. The chapter also covers Oersted's discovery of the magnetic effect of electric current, leading to the working principles of electromagnets and electric bells. Understanding these concepts is crucial for Class 8 Haryana (BSEH) students as they form the foundation for physics in higher classes and frequently appear in board examinations through conceptual questions and numericals.
Start Learning FreeKey Concepts
Heating Effect of Electric Current
When an electric current passes through a high-resistance wire (like nichrome), the wire gets very hot and produces heat energy.
Electric Fuse
A safety device made of a special alloy with a low melting point that melts and breaks the circuit when excessive current flows through it.
Magnetic Effect of Electric Current
An electric current flowing through a wire creates a magnetic field around it, causing a nearby compass needle to deflect.
Electromagnet
A temporary magnet made by wrapping an insulated copper wire around an iron core and passing an electric current through it.
Electric Bell
An everyday device that uses the magnetic effect of current and an electromagnet to ring continuously when the switch is pressed.
Important Formulas
Board Exam Info
In the Haryana (BSEH) Class 8 Science exams, this chapter typically carries around 6 to 8 marks. Questions usually include 1-mark objective questions, 2-mark short answers explaining definitions like fuses or electromagnets, and 3-mark descriptive questions on the working of an electric bell or the factors affecting electromagnets.
Frequently Asked Questions
Why does a fuse wire melt when excess current flows?
A fuse wire has a low melting point and high resistance, so when a heavy current passes through it, it overheats quickly and melts to break the circuit.
What is the difference between a permanent magnet and an electromagnet?
A permanent magnet retains its magnetism for a long time, while an electromagnet works only when electric current flows through the coil.
Who discovered the magnetic effect of electric current?
Hans Christian Oersted discovered the magnetic effect of electric current in 1820 when he noticed a compass needle deflecting near a current-carrying wire.
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