The diagram shows a current I in a vertical square coil - AQA - A-Level Physics - Question 23 - 2020 - Paper 2
Question 23
The diagram shows a current I in a vertical square coil.
The coil can rotate about an axis OO'.
The plane of the coil is at right angles to a uniform horizontal magn... show full transcript
Worked Solution & Example Answer:The diagram shows a current I in a vertical square coil - AQA - A-Level Physics - Question 23 - 2020 - Paper 2
Step 1
A The forces on the vertical sides of the coil are equal in magnitude and opposite in direction.
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Answer
This statement is correct. The forces acting on the vertical sides of the coil experience equal magnetic forces due to the current passing through them, as per Fleming's left-hand rule. Hence, these forces are equal in magnitude but act in opposite directions.
Step 2
B A non-zero couple acts on the coil.
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Answer
This statement is incorrect. Because the forces on opposite sides of the coil are equal in magnitude and opposite in direction, there is no resultant torque (or couple) acting to cause rotation.
Step 3
C No forces act on the horizontal sides of the coil.
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This statement is also correct. Since the horizontal sides of the coil are parallel to the magnetic field lines, they do not experience any force.
Step 4
D The forces on all sides of the coil act toward the centre of the coil.
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Answer
This statement is incorrect. As established, forces do not act on the horizontal sides, and therefore they cannot act toward the center.
