Magnetic Field
Q. What is the magnetic field at the midpoint of a wire carrying current I in opposite directions?
A.
Zero
B.
μ₀I/2
C.
μ₀I
D.
Depends on distance
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Solution
At the midpoint, the magnetic fields due to the two currents cancel each other out, resulting in zero net magnetic field.
Correct Answer: A — Zero
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Q. What is the magnetic field due to a magnetic dipole at a point along its axial line?
A.
(μ₀/4π) * (2m/r³)
B.
(μ₀/4π) * (m/r³)
C.
(μ₀/4π) * (m/r²)
D.
(μ₀/4π) * (m/r⁴)
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Solution
The magnetic field due to a magnetic dipole at a point along its axial line is given by B = (μ₀/4π) * (2m/r³).
Correct Answer: A — (μ₀/4π) * (2m/r³)
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Q. What is the magnetic field inside a hollow conductor carrying current?
A.
Zero
B.
Uniform
C.
Varies with distance
D.
Depends on the current
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Solution
According to Ampere's law, the magnetic field inside a hollow conductor carrying current is zero.
Correct Answer: A — Zero
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Q. What is the magnetic field inside a long solenoid carrying current I?
A.
Zero
B.
μ₀nI
C.
μ₀I/n
D.
μ₀I/2
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Solution
The magnetic field inside a long solenoid is given by B = μ₀nI, where n is the number of turns per unit length.
Correct Answer: B — μ₀nI
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Q. What is the magnetic field inside a long solenoid carrying current?
A.
Zero
B.
Uniform and parallel to the axis
C.
Varies with distance
D.
Depends on the current only
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Solution
The magnetic field inside a long solenoid is uniform and parallel to the axis of the solenoid.
Correct Answer: B — Uniform and parallel to the axis
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Q. What is the magnetic field inside a long solenoid with n turns per unit length carrying a current I?
A.
μ₀nI
B.
μ₀I/n
C.
μ₀I/2n
D.
μ₀I/4n
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Solution
The magnetic field inside a long solenoid is given by B = μ₀nI.
Correct Answer: A — μ₀nI
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Q. What is the magnetic field inside a long, ideal solenoid carrying current?
A.
Zero
B.
Uniform and parallel
C.
Concentric circles
D.
Decreasing
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Solution
The magnetic field inside a long, ideal solenoid is uniform and parallel to the axis of the solenoid.
Correct Answer: B — Uniform and parallel
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Q. What is the magnetic field inside a long, ideal solenoid?
A.
Zero
B.
Uniform and parallel
C.
Concentric circles
D.
Diverging lines
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Solution
The magnetic field inside a long, ideal solenoid is uniform and parallel.
Correct Answer: B — Uniform and parallel
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Q. What is the magnetic field inside a long, straight solenoid carrying current I?
A.
0
B.
μ₀I
C.
μ₀nI
D.
μ₀nI/2
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Solution
The magnetic field inside a long, straight solenoid is given by B = μ₀nI, where n is the number of turns per unit length and μ₀ is the permeability of free space.
Correct Answer: C — μ₀nI
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Q. What is the magnetic field inside a long, straight solenoid carrying current?
A.
Zero
B.
Uniform and parallel to the axis
C.
Varies with distance
D.
Concentric circles
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Solution
The magnetic field inside a long, straight solenoid is uniform and parallel to the axis of the solenoid, given by B = μ₀nI, where n is the number of turns per unit length.
Correct Answer: B — Uniform and parallel to the axis
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Q. What is the magnetic field inside a solenoid carrying current I with n turns per unit length?
A.
μ₀nI
B.
μ₀I/n
C.
μ₀I
D.
μ₀nI/2
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Solution
The magnetic field inside a long solenoid is given by B = μ₀nI.
Correct Answer: A — μ₀nI
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Q. What is the magnetic field strength at the center of a square loop of side a carrying a current I?
A.
(μ₀I)/(2a)
B.
(μ₀I)/(4a)
C.
(μ₀I)/(√2a)
D.
(μ₀I)/(8a)
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Solution
The magnetic field at the center of a square loop is given by B = (μ₀I)/(√2a).
Correct Answer: C — (μ₀I)/(√2a)
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Q. What is the right-hand rule used for in magnetism?
A.
To determine the direction of current
B.
To find the direction of magnetic field
C.
To find the direction of force on a charge
D.
All of the above
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Solution
The right-hand rule helps determine the direction of current, magnetic field, and force on a charge in magnetic fields.
Correct Answer: D — All of the above
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Q. What is the shape of the magnetic field lines around a bar magnet?
A.
Straight lines
B.
Concentric circles
C.
Closed loops
D.
Random
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Solution
The magnetic field lines around a bar magnet form closed loops, exiting from the north pole and entering the south pole.
Correct Answer: C — Closed loops
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Q. What is the unit of magnetic field strength?
A.
Tesla
B.
Newton
C.
Coulomb
D.
Volt
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Solution
The unit of magnetic field strength is the Tesla (T), which is defined as one weber per square meter.
Correct Answer: A — Tesla
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Q. Which of the following statements is true about magnetic field lines?
A.
They can cross each other
B.
They are closed loops
C.
They start from south and end at north
D.
They are always straight lines
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Solution
Magnetic field lines are closed loops; they do not start or end but continue infinitely.
Correct Answer: B — They are closed loops
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Q. Which of the following statements is true regarding magnetic field lines?
A.
They can cross each other
B.
They are always straight
C.
They form closed loops
D.
They originate from magnetic monopoles
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Solution
Magnetic field lines form closed loops, meaning they exit from the north pole and enter the south pole, and they do not cross each other.
Correct Answer: C — They form closed loops
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Q. Which of the following statements is true regarding the Earth's magnetic field?
A.
It is uniform everywhere
B.
It has a magnetic north and south pole
C.
It is only present at the equator
D.
It does not affect compass needles
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Solution
The Earth's magnetic field has a magnetic north and south pole and affects compass needles, causing them to align with the field.
Correct Answer: B — It has a magnetic north and south pole
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