Q. A circular loop of wire carrying current produces a magnetic field. What is the shape of the magnetic field lines inside the loop? (2020)
A.
Straight lines
B.
Concentric circles
C.
Parallel lines
D.
Uniform field
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Solution
Inside the loop, the magnetic field lines are nearly uniform and parallel, indicating a strong and consistent magnetic field.
Correct Answer: D — Uniform field
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Q. A circular loop of wire carrying current produces a magnetic field. What is the shape of the magnetic field lines? (2020)
A.
Straight lines
B.
Concentric circles
C.
Ellipses
D.
Spirals
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Solution
The magnetic field lines around a circular loop of wire are concentric circles centered on the axis of the loop.
Correct Answer: B — Concentric circles
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Q. In which direction does the magnetic field point inside a solenoid carrying current? (2023)
A.
From south to north
B.
From north to south
C.
Perpendicular to the axis
D.
It is zero
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Solution
Inside a solenoid, the magnetic field lines run from the north pole to the south pole, similar to a bar magnet.
Correct Answer: B — From north to south
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Q. What happens to the magnetic field strength inside a long solenoid if the current is doubled? (2021)
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
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Solution
The magnetic field strength inside a solenoid is directly proportional to the current flowing through it. Therefore, doubling the current will double the magnetic field strength.
Correct Answer: B — It doubles
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Q. What happens to the magnetic field strength inside a solenoid if the current is increased? (2021)
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
The magnetic field strength inside a solenoid is directly proportional to the current flowing through it.
Correct Answer: C — It increases
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Q. What happens to the magnetic field strength inside a solenoid if the current through it is doubled? (2021)
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
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Solution
The magnetic field strength inside a solenoid is directly proportional to the current flowing through it. Therefore, if the current is doubled, the magnetic field strength also doubles.
Correct Answer: B — It doubles
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Q. What happens to the magnetic field when the direction of current in a wire is reversed? (2023)
A.
The magnetic field remains unchanged
B.
The magnetic field direction reverses
C.
The magnetic field strength increases
D.
The magnetic field strength decreases
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Solution
Reversing the direction of current in a wire reverses the direction of the magnetic field around it.
Correct Answer: B — The magnetic field direction reverses
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Q. What is the direction of the magnetic field due to a current flowing in a circular loop when viewed from above? (2023)
A.
Out of the plane
B.
Into the plane
C.
Clockwise
D.
Counterclockwise
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Solution
Using the right-hand rule, if the current flows in a counterclockwise direction when viewed from above, the magnetic field direction is out of the plane.
Correct Answer: A — Out of the plane
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Q. What is the direction of the magnetic field produced by a current-carrying wire when viewed from one end? (2023)
A.
Always towards the wire
B.
Always away from the wire
C.
Depends on the direction of current
D.
Always perpendicular to the wire
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Solution
The direction of the magnetic field produced by a current-carrying wire depends on the direction of the current, as determined by the right-hand rule.
Correct Answer: C — Depends on the direction of current
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Q. What is the effect of reversing the direction of current in a loop of wire on the magnetic field it produces? (2019)
A.
The magnetic field disappears
B.
The magnetic field direction reverses
C.
The magnetic field strength increases
D.
The magnetic field becomes weaker
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Solution
Reversing the direction of current in a loop of wire reverses the direction of the magnetic field produced by that loop.
Correct Answer: B — The magnetic field direction reverses
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Q. What is the effect of reversing the direction of current in a loop of wire on the magnetic field? (2019)
A.
The magnetic field direction remains the same
B.
The magnetic field direction reverses
C.
The magnetic field strength increases
D.
The magnetic field strength decreases
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Solution
Reversing the direction of current in a loop of wire reverses the direction of the magnetic field produced by the loop.
Correct Answer: B — The magnetic field direction reverses
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Q. What is the effect of reversing the direction of current in a loop on the magnetic field direction? (2019)
A.
The magnetic field direction remains unchanged
B.
The magnetic field direction reverses
C.
The magnetic field disappears
D.
The magnetic field becomes weaker
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Solution
Reversing the direction of current in a loop reverses the direction of the magnetic field produced by the loop.
Correct Answer: B — The magnetic field direction reverses
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Q. What is the effect of reversing the direction of current in a wire on the magnetic field around it? (2019)
A.
The magnetic field disappears
B.
The magnetic field direction reverses
C.
The magnetic field strength increases
D.
The magnetic field strength decreases
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Solution
Reversing the direction of current in a wire reverses the direction of the magnetic field around it.
Correct Answer: B — The magnetic field direction reverses
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Q. What is the magnetic field inside a toroidal solenoid? (2023)
A.
Zero
B.
Uniform and non-zero
C.
Varies with position
D.
Depends on the current only
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Solution
The magnetic field inside a toroidal solenoid is uniform and non-zero, and it is given by B = (μ₀NI)/(2πr), where N is the number of turns, I is the current, and r is the distance from the center.
Correct Answer: B — Uniform and non-zero
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Q. What is the magnetic field strength at a distance 'r' from a long straight conductor carrying current 'I'? (2020)
A.
μ₀I/2πr
B.
μ₀I/4πr
C.
2μ₀I/πr
D.
μ₀I/πr
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Solution
The magnetic field strength (B) at a distance 'r' from a long straight conductor is given by the formula B = μ₀I/2πr.
Correct Answer: A — μ₀I/2πr
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Q. What is the shape of the magnetic field lines around a circular loop of wire carrying current? (2021)
A.
Straight lines
B.
Concentric circles
C.
Ellipses
D.
Spirals
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Solution
The magnetic field lines around a circular loop of wire carrying current are in the shape of concentric circles, with the center of the loop being the point of maximum field strength.
Correct Answer: B — Concentric circles
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Q. Which of the following devices uses the magnetic effects of current? (2023)
A.
Electric motor
B.
Battery
C.
Resistor
D.
Capacitor
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Solution
An electric motor operates based on the magnetic effects of current, converting electrical energy into mechanical energy.
Correct Answer: A — Electric motor
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Q. Which of the following devices uses the principle of electromagnetism? (2019)
A.
Electric motor
B.
Thermometer
C.
Barometer
D.
Hydrometer
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Solution
An electric motor operates on the principle of electromagnetism, converting electrical energy into mechanical energy.
Correct Answer: A — Electric motor
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Q. Which of the following statements is true about the magnetic field due to a current-carrying loop? (2020)
A.
It is uniform everywhere
B.
It is strongest at the center of the loop
C.
It is zero at the center of the loop
D.
It is strongest at the edges of the loop
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Solution
The magnetic field due to a current-carrying loop is strongest at the center of the loop and decreases as you move away from the center.
Correct Answer: B — It is strongest at the center of the loop
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Q. Which of the following statements is true about the magnetic field due to a long straight conductor? (2020)
A.
It is uniform and constant
B.
It decreases with distance from the conductor
C.
It increases with distance from the conductor
D.
It is only present at the ends of the conductor
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Solution
The magnetic field due to a long straight conductor decreases with increasing distance from the conductor.
Correct Answer: B — It decreases with distance from the conductor
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Q. Which of the following statements is true about the magnetic field inside a solenoid? (2019)
A.
It is zero
B.
It is uniform and parallel to the axis
C.
It varies with distance from the center
D.
It is stronger at the ends
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Solution
Inside a long solenoid, the magnetic field is uniform and parallel to the axis of the solenoid, provided the solenoid is long enough.
Correct Answer: B — It is uniform and parallel to the axis
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Q. Which of the following statements is true regarding the magnetic field due to a solenoid? (2023)
A.
It is uniform inside and zero outside
B.
It is zero inside and uniform outside
C.
It is uniform both inside and outside
D.
It varies linearly with distance
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Solution
A solenoid produces a uniform magnetic field inside and negligible field outside when it is long compared to its diameter.
Correct Answer: A — It is uniform inside and zero outside
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Q. Which of the following statements is true regarding the magnetic field inside a long solenoid? (2023)
A.
It is zero
B.
It is uniform and parallel to the axis
C.
It varies with distance from the center
D.
It is stronger at the ends
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Solution
Inside a long solenoid, the magnetic field is uniform and parallel to the axis of the solenoid, provided the solenoid is long enough.
Correct Answer: B — It is uniform and parallel to the axis
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