A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern. (a) Draw a diagram to show this pattern of iron filings. (b) Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines. (c) (i) How is the direction of magnetic field at a point determined using the field lines? Why do two magnetic field lines not cross each other? OR (ii) How are the magnetic field lines of a bar magnet drawn using a small compass needle? Draw one magnetic field line each on both sides of the magnet.
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern. (a) Draw a diagram to show this pattern of iron filings. (b) Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines. (c) (i) How is the direction of magnetic field at a point determined using the field lines? Why do two magnetic field lines not cross each other? OR (ii) How are the magnetic field lines of a bar magnet drawn using a small compass needle? Draw one magnetic field line each on both sides of the magnet.
(a) Diagram of Iron Filings Pattern
When iron filings are sprinkled around a bar magnet and the board is tapped, they align along the magnetic field lines, forming crowded curves near the poles where the magnetic field is strongest.
(b) Magnetic Field Lines of a Bar Magnet
The magnetic field lines emerge from the North pole () and merge at the South pole (). Inside the magnet, the direction of field lines is from its South pole to its North pole.
(c)
#### (i)
- Determination of Direction: The direction of the magnetic field at any point is determined by placing a small compass needle at that point. The direction in which the north pole of the compass needle points gives the direction of the magnetic field at that point (or the tangent drawn to the field line at that point).
- Why Field Lines Do Not Cross: No two magnetic field lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two different directions simultaneously, which is physically impossible.
#### OR
#### (ii) Drawing Magnetic Field Lines using a Compass Needle
- Place a bar magnet on a sheet of paper and mark its boundary.
- Place a small compass near the North pole of the magnet. The south pole of the compass needle points towards the North pole of the magnet, and its north pole points away.
- Mark the positions of the two ends (north and south poles) of the compass needle with dots on the paper.
- Move the compass to a new position such that its south pole occupies the position previously occupied by its north pole, and mark the new position of its north pole.
- Repeat this step-by-step process until the compass needle reaches the South pole of the magnet.
- Join the marked points with a smooth curve to obtain a magnetic field line. Repeat on both sides of the magnet to get field lines on both sides.
Marking Scheme
- 11 mark
- 21 mark
- 32 marks
- 42 marks
Hint
Remember that magnetic field lines are closed curves. They emerge from the North pole and enter the South pole externally, but travel from South to North internally.
Quick Oral Answer
Magnetic field lines never intersect because if they did, a compass placed at the intersection point would point in two directions at once, which is impossible.
Analysis & Explanation
The alignment of iron filings demonstrates that a magnetic field exists around a bar magnet. The filings experience a magnetic force that aligns them along the magnetic field lines. The density of these lines represents the relative strength of the magnetic field, which is strongest at the poles where the lines are highly crowded. The non-intersection of field lines is a fundamental property arising from the uniqueness of the magnetic field vector at any given point in space.
Common Mistakes
- 1Drawing magnetic field lines that cross each other.
- 2Forgetting to draw arrows indicating the direction of the field lines (from North to South externally).
- 3Not showing that the field lines continue inside the magnet from South to North.
Interesting Facts
The unit of magnetic field strength is named the 'oersted' in honor of Hans Christian Oersted, who accidentally discovered electromagnetism in 1820.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2022?
This question carries 4 marks in the CBSE Class 10 Science 2022 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 "Magnetic Field and Field Lines of a Bar Magnet" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2022 paper?
This question appears in Section C in the CBSE Class 10 Science 2022 paper.