Magnetic Effects of Electric Current — Question 9
Back to all questionsQuestion 9
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Earth wire is used as a safety measure to ensure that any leakage of current to the metallic body of appliances does not give any severe shock to the user.
Earthing metallic appliances provides a low-resistance conducting path for the current. Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.
Chapter 12: Magnetic Effects of Electric Current — Quick Revision Guide
Introduction
Electric current creates magnetic fields, and changing magnetic fields can generate electric current. This chapter covers magnetic field patterns, electromagnets, electric motors, generators, and domestic wiring.
Key Points at a Glance
- Oersted's experiment: current-carrying wire deflects compass needle — current produces magnetic field
- Straight wire: concentric circular field lines; right-hand thumb rule for direction
- Solenoid: uniform field inside (like bar magnet); electromagnet = solenoid + soft iron core
- Force on current-carrying conductor in magnetic field; Fleming's Left-Hand Rule: F(thumb), B(forefinger), I(middle)
- Electric motor: electrical → mechanical energy; coil + magnets + split ring commutator + brushes
- Electromagnetic induction (Faraday): changing magnetic flux induces current; relative motion required
- Fleming's Right-Hand Rule (generator): B(forefinger), motion(thumb), induced current(middle)
- Electric generator: mechanical → electrical energy; AC generator uses slip rings; DC uses split rings
- AC advantage: long-distance transmission via transformers (step-up reduces current, minimises I2R loss)
- Domestic circuit: live (220V) + neutral + earth; fuse/MCB for overload protection; earthing for safety
Real-World Connections
Electric motors in fans, mixers, vehicles; generators in power stations; MRI uses powerful electromagnets; household circuit safety with fuses, MCBs, and earthing.
Quick Self-Test (5 Questions)
- What is the most important concept you learned from this chapter?
- Can you write three key equations/formulae from this chapter from memory?
- Draw a labelled diagram relevant to this chapter without looking at your notes.
- Explain one real-world application of a concept from this chapter.
- What is one common mistake students make in this chapter, and how can you avoid it?
Further Study
- NCERT Textbook Chapter 12
- NCERT Exemplar Problems
- Bright Tutorials Detailed Notes: ch12-magnetic-effects.html
- Bright Tutorials Practice Questions: ch12-magnetic-effects.html
- Previous Year CBSE Board Papers