Question

A flip coil consits of `N` turns of circular coils which lie in a uniform magnetic field. Plane of the coils is perpendicular to the magnetic field as shown in figure. The coil is connected to a current integrator which measures the total charge passing through it. The coil is turned through `180^(@)` about the diameter. The charge passing through the coil is

A. `(NBA)/(R )`
B. `(sqrt(3) NBA)/(2R)`
C. `(NBA)/(sqrt(2)A)`
D. `(2NBA)/(R )`

Answer 1

Correct Answer - D
Initial flux through the coil, `phi_(Bi) = +NBA`
Final flux through the coil, `phi_(Bi) = +NBA`
When the coil is turned through `180^(@)` its flux reverses, the angle between magntic field and area vector is reversed.
`Delta phi_(B) = phi_(Bf) - phi_(Bi) = -NBA-(NBA) = -2NBA`
`Q = (Delta phi_(B))/(R ) = (2NBA)/(R )`