A coil is placed in a magnetic field and has a flux Φ_B through it.The coil is stressed so that its area reduces to 75% of its original value.If the plane of the coil stays the same and the flux through it remains the same,how must the magnetic field change? A)It must increase by 25%. B)It must increase by 33%. C)It must increase by 125%. D)It must decrease by 25%.

Question

Quizplus · Accepted Answer

The magnetic flux (Φ) through a coil is given by the product of the magnetic field (B), the area of the coil (A), and the cosine of the angle (θ) between the magnetic field and the normal to the area (Φ = B*A*cos(θ)). If the area is reduced to 75% of its original value and the flux remains the same, the magnetic field must increase to compensate for the decrease in area. To maintain the same flux, if the area is reduced to 75% (or 3/4), the magnetic field must increase by a factor of 4/3, which is an increase of 33%.

A Coil Is Placed in a Magnetic Field and Has