Electromagnetism

(a) Definition of solenoid
A solenoid is a long cylindrical coil of many closely wound turns of insulated copper wire through which electric current flows. (b) Correctness of statement
Step 1: Concept of polarity}
The polarity of a solenoid depends on the direction of current. Step 2: Right-hand thumb rule}
If we curl the fingers of the right hand in the direction of current, the thumb points towards the North pole. Step 3: Conclusion}
The given statement is incorrect because:

• The terminal connected to positive does not always become North.
• It depends on the direction of current in the coil.

Final Answer (b): (c) Ways to increase magnetic field strength
Step 1: Methods}}

• Increase the current through the solenoid
• Increase the number of turns (coils)
• Insert a soft iron core inside the solenoid

Any two:

Concept: Fleming’s Right-Hand Rule
Step 1: Identify the figure}
The diagram shows three mutually perpendicular directions using the thumb, forefinger, and middle finger of the right hand. Step 2: Name of the rule}
This represents: Step 3: Statement of the rule}
If the thumb, forefinger, and middle finger of the right hand are held mutually perpendicular to each other, then:

• Thumb → direction of motion of conductor
• Forefinger → direction of magnetic field
• Middle finger → direction of induced current

Step 4: Application}
This rule is used in:

• Electric generators
• Electromagnetic induction problems

Conclusion:

Concept: Types of Magnets

• Permanent magnets (like bar magnets)
• Electromagnets (like current carrying solenoids)

Step 1: Bar magnet properties}
Bar magnet:

• Magnetism is permanent → (B)
• Polarity cannot be changed → (F)

So: Step 2: Current carrying solenoid properties}
Solenoid:

• Polarity can be changed → (C)
• Magnetic strength can be varied → (E)

So: Step 3: Match with options}
Correct pairing: Conclusion: