This chapter shows that an electric current does more than light a lamp. When current flows through a wire, it produces a magnetic field around it, deflecting a nearby compass needle; this is the magnetic effect of electric current, first discovered by Hans Christian Oersted. A coil of wire carrying current behaves like a magnet, and inserting an iron core makes a much stronger electromagnet with two poles. The strength of an electromagnet can be increased by using more cells (more current) or more turns of the coil, and its poles reverse if the current direction reverses. Lifting electromagnets on cranes use this on-off control to move heavy iron and steel. The chapter also studies the heating effect: a current-carrying conductor faces resistance, converting some electrical energy into heat. Nichrome wire has high resistance and is used in heaters, irons, kettles, and immersion rods. The heat generated depends on the current, and on the material, thickness, length, and time. Finally, the chapter explains how cells and batteries generate electricity through chemical reactions. It describes the Voltaic (Galvanic) cell with electrodes and an electrolyte, a homemade lemon cell, dry cells with a moist paste electrolyte, and modern rechargeable batteries, including a note on lithium-ion and the value of safe e-waste recycling.
Magnetic effect of currentElectromagnets and their strengthHeating effect of currentCells and batteriesVoltaic, dry, and rechargeable cells
Key terms
Magnetic effect of electric current
The production of a magnetic field around a conductor when an electric current flows through it.
Magnetic field
The region around a magnet or current-carrying wire where its magnetic effect can be felt.
Electromagnet
A current-carrying coil that behaves as a magnet, usually made stronger with an iron core.
Heating effect of electric current
The generation of heat in a conductor due to its resistance when current flows through it.
Resistance
The opposition a conductor offers to the flow of electric current, causing heating.
Electrolyte
The liquid or moist paste in a cell that takes part in the chemical reaction producing electric current.
Extra questions & answers
Probe and ponder
Keep the curiosity alive
Discover, design, and debate
Try one from this chapter
What happens to a compass needle placed near a wire when current flows?
Flashcards & interactive practice
Practice quiz · Electricity: Magnetic and Heating Effects
Score on this chapter, climb the leaderboard, and get an AI diagnosis of your mistakes.
Double-checked questions Real exam pattern 1 free test every month, then ₹9 per test
#1
Electricity: Magnetic and Heating Effects
Start here
Science 10 Qs · ~10 min
Instant score, answer review and weak-topic diagnosis
Data & insights
Trending in Class 8 this monthThe chapters students are reading most right now
