Bar Magnet and Magnetic Field Lines - UNSOLVED PRACTICE SET
Chapter: Magnetism and Matter | Topic: Bar Magnet and Magnetic Field Lines
BAR MAGNET AND MAGNETIC FIELD LINES - UNSOLVED PRACTICE SET
Topic: Bar Magnet and Magnetic Field Lines
Multiple Choice Questions
Q1. When a bar magnet is broken into two pieces, each piece:
- Loses all magnetic properties
- Becomes a single magnetic pole
- Behaves as a complete magnet with both poles
- Becomes demagnetized
Q2. The direction of magnetic field lines outside a bar magnet is from:
- South pole to North pole
- North pole to South pole
- Centre to both poles
- Random directions
Q3. At which point is the magnetic field of a bar magnet the strongest?
- At the centre of the magnet
- At the equatorial line, far from poles
- Near the poles of the magnet
- At infinity
Q4. Magnetic field lines of a bar magnet:
- Can intersect at the neutral point
- Never form closed loops
- Form continuous closed loops from North to South pole
- Are always parallel to each other
Q5. The property of magnetic field lines that indicates the strength of the magnetic field is:
- Their colour
- Their direction
- Their closeness (density)
- Their length
Q6. A compass needle placed near the north pole of a bar magnet will point:
- Away from the north pole
- Towards the north pole
- Perpendicular to the bar magnet
- In a random direction
Short Answer Questions
Q7. Why do magnetic field lines never intersect each other? Explain with reasoning.
Q8. Describe an experiment using iron filings to visualize the magnetic field lines around a bar magnet. What pattern do you observe?
Q9. What is a neutral point in the magnetic field of a bar magnet? Where are neutral points located when a bar magnet is placed in Earth's magnetic field with its north pole pointing north?
Q10. A student places two bar magnets close to each other with their north poles facing each other. Draw a rough sketch of the magnetic field lines in this arrangement.
Q11. Why does the density of magnetic field lines increase near the poles of a bar magnet?
Q12. Compare the magnetic field pattern of a bar magnet with that of a current-carrying circular loop.
Long Answer Questions
Q13. Derive the expression for the magnetic field at a point on the axial line of a bar magnet. State the assumptions made.
Q14. Explain with a diagram how you would locate the neutral points for a bar magnet placed in the magnetic meridian with its north pole pointing towards geographic north. What is the significance of these neutral points?
Q15. A bar magnet is placed on a table and iron filings are sprinkled around it. The filings arrange themselves in a definite pattern. Explain this phenomenon and describe what happens if the magnet is heated to a very high temperature.
Numerical & Application-Based Problems
Q16. A bar magnet of length 12 cm has pole strength 30 Am.
(a) Calculate its magnetic moment.
(b) Find the magnetic field at a point on its axial line at a distance of 10 cm from its centre.
(c) Compare this value with the field at the same distance on the equatorial line.
Q17. Two identical bar magnets, each of magnetic moment 20 Am², are placed parallel to each other with their axes along the same line and their opposite poles facing each other, separated by a distance of 10 cm.
(a) Calculate the magnetic field at the midpoint between the two magnets.
(b) If a small compass needle is placed at this midpoint, in which direction will it point?
Q18. In your school's science fair, a student demonstrates magnetic field lines using a bar magnet and a compass. The bar magnet has a length of 8 cm and pole strength 25 Am. The student places the magnet horizontally and marks a point P at a distance of 12 cm from the centre of the magnet on the axial line.
(a) Calculate the magnetic field at point P due to the bar magnet.
(b) If the horizontal component of Earth's magnetic field at that location is 0.4 G, will the compass needle at point P align exactly with the magnet's axis? Justify your answer with calculation.