A coil of insulated wire is connected to a galvanometer. What would be seen if a bar magnet with its north pole towards one face of the coil is (i) moved quickly towards it, (ii) moved quickly away from the coil and (iii) placed near its one face ? Name the phenomena involved.
A coil of insulated wire is connected to a galvanometer. What would be seen if a bar magnet with its north pole towards one face of the coil is (i) moved quickly towards it, (ii) moved quickly away from the coil and (iii) placed near its one face ? Name the phenomena involved.
When a bar magnet is interacted with a coil connected to a galvanometer, the following observations are made:
(i) Moved quickly towards the coil: There is a momentary deflection in the galvanometer needle in a specific direction (e.g., to the right), indicating that a current is induced in the coil.
(ii) Moved quickly away from the coil: There is a momentary deflection in the galvanometer needle but in the opposite direction (e.g., to the left), indicating the induced current has reversed its direction.
(iii) Placed near its one face (Stationary): No deflection is observed in the galvanometer, indicating that no current is induced when there is no relative motion between the magnet and the coil.
Phenomena involved: The phenomenon is called Electromagnetic Induction.
Marking Scheme
- 1Observation for moving towards (momentary deflection) (0.5 marks)
- 2Observation for moving away (opposite deflection) (0.5 marks)
- 3Observation for stationary magnet (no deflection) (0.5 marks)
- 4Naming the phenomenon: Electromagnetic Induction (0.5 marks)
Hint
Think about what causes the galvanometer needle to move—is it the presence of the magnet or the motion of the magnet?
Quick Oral Answer
Moving a magnet near a coil induces a current due to Electromagnetic Induction. Moving it towards or away causes deflections in opposite directions, while keeping it still results in no current.
Analysis & Explanation
The NCERT text introduces the 'reverse possibility' of electricity being produced by moving magnets. This is known as electromagnetic induction. The galvanometer detects the presence of current. The deflection only occurs when the magnetic field linked with the coil changes, which happens during the relative motion (moving towards or away). When stationary, the magnetic flux is constant, so no current is induced.
Common Mistakes
- 1Stating that a stationary magnet induces current.
- 2Forgetting to mention that the deflection is 'momentary'.
Interesting Facts
Electromagnetic induction is the fundamental principle behind the working of electric generators that power our homes.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2010?
This question carries 2 marks in the CBSE Class 10 Science 2010 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Magnetic Effects of Electric Current" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Electromagnetic Induction" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2010 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2010 paper.