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Q1. Which device works on the magnetic effect of electric current?
An electric motor works on the magnetic effect of electric current. When current flows through a coil placed in a magnetic field, a force acts on the coil, causing it to rotate. This converts electrical energy into mechanical energy. A generator works on the reverse principle (electric effect of moving magnets).
Q2. Field lines show the path along which a:
Magnetic field lines show the path along which a north pole would move if placed in the field. The direction of field lines is from the north pole to the south pole outside the magnet. This convention helps us visualize the magnetic field.
Q3. The north pole of compass needle seeks:
The north pole of a compass needle seeks the north direction because it is attracted towards the Earth’s magnetic south pole (which is located near the geographic north). This is why a compass always points north.
Q4. What is created around a current-carrying straight wire?
A magnetic field is created around a current-carrying straight wire. This was discovered by Oersted. The magnetic field lines form concentric circles around the wire. The direction of the field depends on the direction of current flow.
Q5. Which pole of compass is directed away from north pole of magnet?
The north pole of a compass needle is directed away from the north pole of a magnet because like poles repel each other. The north pole of the compass is attracted towards the south pole of the magnet.
Q6. Salt sprinkler is used to:
A salt sprinkler is used to sprinkle iron filings uniformly on a sheet of paper placed over a magnet. This helps in observing the pattern of magnetic field lines clearly. Uniform distribution of filings gives a better field pattern.
Q7. The south pole of the compass needle points towards the:
The south pole of a compass needle points towards the north pole of a magnet because unlike poles attract each other. This is why the south pole of the compass points towards the north direction (which is actually Earth’s magnetic south pole).
Q8. Like poles of magnets:
Like poles of magnets (north-north or south-south) repel each other. This is a fundamental property of magnets. Unlike poles (north-south) attract each other.
Q9. Magnetic field lines never:
Magnetic field lines never cross each other. If they did, it would mean that at the point of intersection, the magnetic field would have two directions, which is impossible. Field lines always form closed curves.
Q10. Deflection of compass needle indicates the presence of:
Deflection of a compass needle indicates the presence of a magnetic field. The compass needle aligns itself along the magnetic field lines. The amount of deflection shows the strength of the magnetic field.
Q11. The unit of magnetic field strength is named after:
The SI unit of magnetic field strength (magnetic flux density) is the tesla (T). It is named after Nikola Tesla, a Serbian-American inventor who made significant contributions to electromagnetism. One tesla is a very strong magnetic field.
Q12. Which material is used to fix paper on drawing board in activities?
In magnetic field experiments, glue or adhesive is used to fix the paper on the drawing board so that it stays in place while sprinkling iron filings and tracing field lines. Pins or tape may also be used.
Q13. Field lines are drawn by joining points marked by:
Field lines are drawn by joining points marked by compass needle positions. By placing a compass at different points and marking the direction of the north pole, a smooth curve is drawn showing the magnetic field lines.
Q14. The magnetic field around a magnet can be detected using:
A compass is used to detect the magnetic field around a magnet. The compass needle deflects and aligns itself along the magnetic field lines. Wood, plastic, and paper are non-magnetic and do not detect magnetic fields.
Q15. What happens to the compass needle when current flows through a nearby wire?
When current flows through a nearby wire, the compass needle deflects. This was Oersted’s famous experiment. The current produces a magnetic field around the wire, which affects the compass needle.
Q16. Which effect of electric current is discussed other than heating effect in the chapter?
The chapter discusses the magnetic effect of electric current in addition to the heating effect. The magnetic effect is the basis for electric motors, generators, and many other devices.
Q17. The study of magnetic fields is included in the chapter on:
The study of magnetic fields is included in the chapter on magnetism and electromagnetic effects. This chapter covers the relationship between electricity and magnetism.
Q18. The magnetic effect of current was discovered accidentally by:
The magnetic effect of electric current was discovered accidentally by Hans Christian Oersted in 1820. He noticed that a compass needle deflected when placed near a current-carrying wire.
Q19. Generators work on the principle of:
Generators work on the principle of the electric effect of moving magnets (electromagnetic induction). When a coil rotates in a magnetic field, an electric current is induced. This converts mechanical energy into electrical energy.
Q20. The magnetic field around a magnet is three-dimensional but shown on paper as:
The magnetic field around a magnet is three-dimensional, but it is shown on paper as lines (field lines). These lines represent the direction and strength of the magnetic field.
Q21. A current-carrying wire behaves like a:
A current-carrying wire behaves like a magnet. It produces a magnetic field around itself. This is the magnetic effect of electric current. The magnetic field lines form concentric circles around the wire.
Q22. Iron filings arrange themselves around a bar magnet because:
Iron filings arrange themselves around a bar magnet because the magnetic force acts on them. They align themselves along the magnetic field lines, showing the pattern of the magnetic field.
Q23. The direction of magnetic field is indicated by:
The direction of the magnetic field is indicated by the north pole of a compass needle. The north pole of the compass points in the direction of the magnetic field lines.
Q24. The end of a compass needle pointing north is called:
The end of a compass needle that points towards the north direction is called the north seeking pole. This is actually a north pole of the magnet, but it points north because it is attracted to Earth’s magnetic south pole.
Q25. The study of relationship between electricity and magnetism is called:
The study of the relationship between electricity and magnetism is called electromagnetism. It deals with the magnetic effects of electric current and the electric effects of moving magnets.
Q26. The reverse possibility studied in the chapter is electric effect of:
The reverse possibility studied in the chapter is the electric effect of moving magnets (electromagnetic induction). When a magnet is moved near a coil, an electric current is induced in the coil.
Q27. Electric motors work on the principle of:
Electric motors work on the principle of the magnetic effect of electric current. The current-carrying coil experiences a force in a magnetic field, causing it to rotate. This converts electrical energy into mechanical energy.
Q28. The deflection of compass needle increases near the:
The deflection of the compass needle is maximum near the poles of a magnet because the magnetic field is strongest there. At the center of the magnet, the field is weaker.
Q29. Oersted observed deflection of compass needle near a:
Oersted observed the deflection of a compass needle near a current-carrying wire. This experiment demonstrated that electric current produces a magnetic field.
Q30. Why does a compass needle get deflected near a bar magnet?
A compass needle gets deflected near a bar magnet because of the magnetic field around the magnet. The compass needle aligns itself with the magnetic field lines, showing the direction of the field.
Q31. The magnetic effect of electric current shows that electricity and magnetism are:
The magnetic effect of electric current shows that electricity and magnetism are interlinked. A current produces a magnetic field, and a changing magnetic field can produce a current. This is the basis of electromagnetism.
Q32. Who discovered the magnetic effect of electric current?
Hans Christian Oersted discovered the magnetic effect of electric current in 1820. He showed that a compass needle deflects when placed near a current-carrying wire.
Q33. Magnetic field is a quantity having:
Magnetic field is a vector quantity. It has both magnitude (strength) and direction. The field lines show the direction, and the spacing of field lines indicates the strength.
Q34. Magnetic field lines are closer near the:
Magnetic field lines are closer near the poles of a magnet because the magnetic field is strongest there. Closer lines indicate a stronger field. Farther apart lines indicate a weaker field.
Q35. Iron filings experience force due to:
Iron filings experience force due to the magnetic force from a magnet. They align themselves along the magnetic field lines, showing the pattern of the field.
Q36. Compass needle deflection proves that current produces:
Compass needle deflection proves that a current-carrying wire produces a magnetic field around it. This was Oersted’s discovery and is the basis of electromagnetism.
Q37. Which instrument is used to draw magnetic field lines?
A compass is used to draw magnetic field lines. By placing the compass at different points around a magnet and marking the direction of the north pole, a smooth curve is drawn to represent the field lines.
Q38. In which year did Oersted discover electromagnetism?
Hans Christian Oersted discovered electromagnetism in 1820. He noticed that a compass needle was deflected when placed near a current-carrying wire.
Q39. The direction of magnetic field is taken as the direction in which the compass:
The direction of the magnetic field is taken as the direction in which the north pole of a compass needle points. This convention is used to define the direction of magnetic field lines.
Q40. The magnetic field is strongest where field lines are:
The magnetic field is strongest where field lines are closely spaced. The density of field lines indicates the strength of the magnetic field. Closer lines mean a stronger field.
Q41. Magnetic field lines show the:
Magnetic field lines show both the strength and direction of the magnetic field. The direction is indicated by the arrow on the lines, and the strength is indicated by the spacing of the lines.
Q42. A compass needle is actually a small:
A compass needle is actually a small bar magnet. It has a north pole and a south pole. It aligns itself with the Earth’s magnetic field, pointing north-south.
Q43. Which scientist’s work led to radio and television technologies?
Michael Faraday’s work on electromagnetic induction led to the development of radio and television technologies. His discovery of induced current is the basis for many modern technologies.
Q44. Which device works on the electric effect of moving magnets?
A generator works on the electric effect of moving magnets (electromagnetic induction). When a coil rotates in a magnetic field, an electric current is induced. This converts mechanical energy into electrical energy.
Q45. Unlike poles of magnets:
Unlike poles of magnets (north and south) attract each other. This is a fundamental property of magnets. Like poles repel each other.
Q46. The compass needle aligns itself along:
The compass needle aligns itself along the magnetic field. It points in the direction of the magnetic field lines. This is how a compass is used to detect magnetic fields.
Q47. The region surrounding a magnet where its force can be detected is called:
The region surrounding a magnet where its force can be detected is called the magnetic field. It is the space around a magnet where other magnets or magnetic materials experience a force.
Q48. Magnetic field lines around a bar magnet form:
Magnetic field lines around a bar magnet form closed curves. They emerge from the north pole, travel through the surrounding space, and enter the south pole. Inside the magnet, they go from south to north, forming closed loops.
Q49. Iron filings are used to study:
Iron filings are used to study the magnetic field. When sprinkled around a magnet, they align themselves along the magnetic field lines, showing the pattern of the field.
Q50. Magnetic field lines are represented by the alignment of:
Magnetic field lines are represented by the alignment of iron filings. When iron filings are sprinkled around a magnet, they arrange themselves along the magnetic field lines, revealing the field pattern.