VARDAAN LEARNING INSTITUTE

1. Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
2. An alpha particle entering a magnetic field experiences a force. Under what condition will this force be zero?
3. A uniform magnetic field is directed vertically upwards. A proton enters the field horizontally from South to North. What is the trajectory of the proton? (Describe path).
4. Why is the magnetic field inside a hollow current carrying solenoid zero? (Think vector cancellation, if applicable, or clarify standard syllabus concept: Field lines are inside core, negligible outside. Inside hollow space, field is uniform).
5. Is the work done by the magnetic force on a moving charge zero? Explain.
6. A current carrying loop is free to turn in a uniform magnetic field. Under what orientation is it in stable equilibrium?
7. How does the resistance of a fuse wire compare with that of the mains connecting wire? (High/Low).
8. Two parallel wires carry current in opposite directions. Do they attract or repel? Using the concept of field lines between them, explain qualitatively.
9. If a current carrying conductor is placed parallel to the magnetic field, what is the torque acting on it?
10. Imagine a world where magnetic monopoles exist. How would Gauss's law for magnetism change? (Concept: $\oint B \cdot dA \neq 0$).
11. A charged particle moves in a circle in a magnetic field. If the speed of the particle is doubled, how does the radius of the path change? ($r = mv/qB$).
12. Can a transformer be used to step up DC voltage? Why or why not?
13. Why do commercial motors use electromagnets instead of permanent magnets?
14. What happens to the fuse wire if a 220V appliance is connected to a 440V supply?
15. In a domestic circuit, if the neutral wire breaks at the pole, what happens to the appliances connected when switched on? (Think potential).

Case I: Biomega-Magnetism

Magnetic fields play a vital role in medical diagnosis. The weak ion currents in our body produce magnetic fields. The two main organs where significant magnetic fields are produced are the heart and the brain. The magnetic field inside the body forms the basis of MRI, which produces images of internal organs.

16. What is the full form of MRI?
17. Which two organs produce the most significant magnetic fields in the human body?
18. How are these magnetic fields generated inside the body?
19. Is the magnetic field of the earth stronger or weaker than the MRI magnetic field?
20. Name the unit of magnetic field used in MRI (Tesla).

Case II: Physics of the Fuse

A fuse is a safety device used in circuits to prevent damage due to overloading or short circuits. It works on the heating effect of current. The fuse wire has a specific melting point and resistance. When current exceeds the safe limit, the heat generated melts the wire and breaks the circuit.

21. Name the alloy used for making fuse wires. Why is it chosen?
22. If a fuse is rated 5A, can it be used for a 2kW geyser operating at 220V? Justify.
23. What determines the thickness of the fuse wire?
24. In which wire (Live/Neutral/Earth) is the fuse always connected?
25. Why should a fuse wire have high resistance compared to connecting wires?

Case III: Electromagnetic Induction

In 1831, Michael Faraday discovered that a changing magnetic field can induce an electric current in a closed coil. This phenomenon is called Electromagnetic Induction. This principle is used in electric generators. The direction of induced current can be found using Fleming's Right Hand Rule.

26. State Faraday's law of electromagnetic induction (Qualitative).
27. If a magnet is held stationary inside a coil, will current be induced?
28. Name the rule used to find the direction of induced current.
29. Is the induced current AC or DC acts in a simple coil rotating in a magnetic field?
30. What conversion of energy takes place during electromagnetic induction in a generator?

Directions: Choose the correct option:

• (a) Both A and R are true and R is the correct explanation of A.
• (b) Both A and R are true but R is NOT the correct explanation of A.
• (c) A is true but R is false.
• (d) A is false but R is true.

31. Assertion: A current carrying solenoid behaves like a bar magnet.
    Reason: The magnetic field lines inside the solenoid are parallel.
32. Assertion: The magnetic field produced by a straight current carrying conductor increases as we move away from it.
    Reason: The magnetic field strength is inversely proportional to the distance from the wire.
33. Assertion: Parallel arrangement is used in domestic circuits.
    Reason: It provides the same voltage to each appliance.
34. Assertion: Fuse wire is made of a material with low melting point.
    Reason: It should melt and break the circuit when current exceeds the safe limit.
35. Assertion: No force acts on a stationary charge placed in a magnetic field.
    Reason: Magnetic force depends on the velocity of the charge.
36. Assertion: In AC generator, split rings are used.
    Reason: Split rings reverse the direction of current. (Check: AC uses Slip rings).
37. Assertion: The Earth wire protects the user from electric shock.
    Reason: It provides a low resistance path for the leakage current.
38. Assertion: Magnetic field lines are closed curves.
    Reason: They start from North pole and end at South pole outside the magnet.
39. Assertion: AC is preferred over DC for long distance transmission.
    Reason: AC can be transmitted with minimum power loss.
40. Assertion: A compass needle does not show deflection when placed near a wire carrying DC.
    Reason: A constant current produces a constant magnetic field. (Deflection occurs! A is False).
41. Assertion: The core of an electromagnet is made of soft iron.
    Reason: Soft iron has low retentivity and high permeability.
42. Assertion: Two magnetic field lines never intersect.
    Reason: At the point of intersection, there would be two directions of the field, which is impossible.
43. Assertion: Work done by the magnetic force on a charged particle moving in a uniform magnetic field is zero.
    Reason: The magnetic force is always perpendicular to the velocity of the particle.
44. Assertion: A 100W bulb glows brighter than a 60W bulb when connected in series.
    Reason: In series, current is same, so $P=I^2R$, and 60W bulb has higher resistance ($R=V^2/P$), so 60W glows brighter. (A is False).
45. Assertion: Fleming's Left Hand Rule gives the direction of induced current.
    Reason: Fleming's Right Hand Rule gives the direction of force. (Both False - Swapped).