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Homework answers / question archive / A conducting loop is halfway into a magnetic field
A conducting loop is halfway into a magnetic field. Supposed the magnetic field begins to increase rapidly in strength. What happens to the loop? Explain your answer fully!!
a. The loop is pushed upward, toward the top of the page.
b. The loop is pushed downward, toward the bottom of the page.
c. The loop is pushed to the left, into the magnetic field.
d. The loop is pushed to the right, out of the magnetic field.
The answer is d.Please explain why the answer is d.
The incorrect options are as follows:
• a) The loop is pushed upward, toward the top of the page.
• b) The loop is pushed downward, toward the bottom of the page.
• c) The loop is pushed to the left, into the magnetic field.
If the magnetic field increases, then the flux will also increase.
Expression for the magnetic flux is as follows:
\Phi = BAΦ=BA
According to Lenz’s law, if the magnetic flux increases, then the current flows in the anticlockwise direction; if the magnetic flux decreases, then the current flows in the clockwise direction.
According to right hand rule, the upper part of the loop creates a force downwards and the lower loop will create a force upward. Therefore due to equal magnitude and their action against each other, their effects will get cancelled.
The current flowing downward at the left loop will create a magnetic force, which is directed towards the right.
Hence, the loop is not pushed upward or downward.
Explanation | Common mistakes | Hint for next step
The right hand part of the loop is not considered because there is no magnetic field acting on the right side of the loop.
Since the expression for magnetic force is F = I(L*B) , if the direction of the current and the direction of the magnetic field is not perpendicular to each other, then the force will not have a physical significance.
The correct answer is as follows:
• d) The loop is pushed to the right, out of the magnetic field.
The current direction is anticlockwise. Also, the force created by the current on the upper loop and lower loop gets cancelled due to opposite direction.
The current flowing through the left loop will create a force which acts towards the right. Hence, the loop is pushed towards the right.
When the magnetic field increases gradually in strength, the loop is pushed to the right, out of the magnetic field.
Explanation | Common mistakes
The current direction is anticlockwise. Also, the force created by the current on the upper loop and lower loop gets cancelled due to opposite direction.
If the magnetic flux increases, then the current flows in the anticlockwise direction. If the magnetic flux decreases, then the current flows in the clockwise direction.
When the magnetic field increases gradually in strength, the loop is pushed to the right, out of the magnetic field.
