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A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of 450 with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the location
  • a)
    0.34G
  • b)
    0.49G
  • c)
    0.29G
  • d)
    0.39G
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
A compass needle free to turn in a horizontal plane is placed at the c...
The needle will point along W-E if the result of the earth’s magnetic field and magnetic field due to the coil have a resultant in the W-E direction. This happens if B cos 45o=Earth's field
⟹ (μ0​nI​/2r) cos45o=(4π×10−7×30×0.35​)/(2×0.12) ×(1/√2)​​=0.39G=Earth's magnetic field.
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Most Upvoted Answer
A compass needle free to turn in a horizontal plane is placed at the c...
To determine the horizontal component of the Earth's magnetic field at the given location, we can use the concept of magnetic field due to a current-carrying coil.

1. Magnetic Field Due to a Current-Carrying Coil:
- When a current flows through a coil, it creates a magnetic field around it.
- The magnetic field at the center of a circular coil is given by the formula:
B = (μ₀ * n * I) / (2 * R)
where B is the magnetic field, μ₀ is the permeability of free space (4π × 10^-7 Tm/A), n is the number of turns in the coil, I is the current flowing through the coil, and R is the radius of the coil.

2. Given Parameters:
- Number of turns in the coil (n) = 30
- Radius of the coil (R) = 12 cm = 0.12 m
- Current flowing through the coil (I) = 0.35 A
- Angle between the coil and the magnetic meridian = 45°

3. Calculation:
- Substituting the given values into the formula, we can calculate the magnetic field at the center of the coil.
B = (4π × 10^-7 Tm/A) * (30 turns) * (0.35 A) / (2 * 0.12 m)
B = 0.00147 T

4. The Earth's Magnetic Field:
- The Earth's magnetic field can be considered as a horizontal component (Bh) and a vertical component (Bv).
- The compass needle aligns with the horizontal component of the Earth's magnetic field.
- Thus, the horizontal component of the Earth's magnetic field (Bh) is equal to the magnetic field at the center of the coil when the needle points west to east.

5. Answer:
- The horizontal component of the Earth's magnetic field at the given location is approximately 0.00147 T or 0.39 G (Gauss) (since 1 T = 10^4 G).
- Therefore, the correct answer is option 'D' (0.39 G).
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A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of450with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the locationa)0.34Gb)0.49Gc)0.29Gd)0.39GCorrect answer is option 'D'. Can you explain this answer?
Question Description
A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of450with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the locationa)0.34Gb)0.49Gc)0.29Gd)0.39GCorrect answer is option 'D'. Can you explain this answer? for Class 12 2024 is part of Class 12 preparation. The Question and answers have been prepared according to the Class 12 exam syllabus. Information about A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of450with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the locationa)0.34Gb)0.49Gc)0.29Gd)0.39GCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 12 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of450with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the locationa)0.34Gb)0.49Gc)0.29Gd)0.39GCorrect answer is option 'D'. Can you explain this answer?.
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