Class 8 Science - BIHAR
Electricity: Magnetic and Heating Effects
In this chapter of Class 8 Science, Bihar Board students will explore the fascinating dual nature of electricity. We study how electric current produces heat, which is used in everyday appliances like electric irons, heaters, and fuses to protect our homes. Furthermore, the chapter covers the magnetic effect of electric current, demonstrating how electricity can create temporary magnets (electromagnets) and operate devices like electric bells. Understanding these concepts is crucial for board exams as questions frequently test practical applications, safety devices, and the working principle of electromagnets.
Start Learning FreeKey Concepts
Heating Effect of Electric Current
When an electric current flows through a wire, the wire gets hot due to the resistance it offers to the flow of electrons, converting electrical energy into heat energy.
Electric Fuse
A safety device made of a special alloy wire with a low melting point that melts and breaks the circuit when excessive current flows through it, preventing fires and damage.
Magnetic Effect of Electric Current
When electric current passes through a wire, it behaves like a magnet and creates a magnetic field around it, first observed by Hans Christian Oersted.
Electromagnet
A temporary magnet made by wrapping an insulated coil of wire around a soft iron core and passing an electric current through it, which loses its magnetism when the current is switched off.
Electric Bell
A common device that uses the magnetic effect of electric current along with an iron armature and a contact screw to produce a continuous ringing sound.
Important Formulas
Board Exam Info
In the Bihar Board Class 8 Science examination, this chapter typically carries around 6 to 8 marks. Questions usually include short-answer questions defining fuses or electromagnets, long-answer questions explaining the working of an electric bell with a diagram, and objective fill-in-the-blanks or multiple-choice questions.
Frequently Asked Questions
Why does a fuse wire melt when a short circuit occurs?
A fuse wire has a low melting point. When a short circuit happens, a very high current flows through the circuit, causing the fuse wire to heat up quickly and melt, which breaks the circuit and stops the current.
How can we increase the strength of an electromagnet?
We can increase the strength of an electromagnet by increasing the amount of electric current flowing through the coil or by increasing the number of turns of wire in the coil.
What is the difference between a normal magnet and an electromagnet?
A normal (permanent) magnet retains its magnetism all the time, whereas an electromagnet is a temporary magnet that only produces a magnetic field when electric current flows through its coil.
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