Test: Magnetic Flux (January 21) - NEET MCQ

The induced emf ,E=− dϕ​/dt where ϕ=magnetic flux
Hence, emf will last as long as flux keeps changing.

When a magnet is moved towards the coil quickly, the rate of change of flux is larger than that if the magnetic field is moved slowly, thus larger emf is induced due to quick movement of the coil.

A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then there is no change in magnetic flux, there is no emf induced in the coil, no current will be induced in the coil.

The measurement of the total magnetic field that passes through a given area is known as magnetic flux. It is helpful in describing the effects of the magnetic force on something occupying a given area.
If we consider a simple flat area A as our example and angle θ as the angle between the normal to the surface and a magnetic field vector, then the magnetic flux is given by the equation:
ϕ=BAcosΘ
 

 The total flux is given by φ = ∫ B.ds, where ∫ds is the area. Thus φ = BA. We get φ = 11.7 x 2 = 23.4 units.

Magnetic Flux Formula
Magnetic flux is the product of the average magnetic field times the perpendicular area that it crosses.
Magnetic flux = number of turns x Magnetic field x Area x (angle between the planar area and the magnetic flux)
The equation is:
Φ =N B A cos(θ)
Where:
N=number of turns
Φ: Magnetic Flux
A: Area
B: Magnetic field
θ: angle between a perpendicular vector to the area and the magnetic field

When an iron rod is inserted inside a solenoid the magnetic field inside the solenoid increases due to the high magnetic permeability of iron. Due to the increased magnetic field, the magnetic flux also increases. The self-inductance of the solenoid also increases because self-inductance (L) of the coil is directly proportional to the permeability of the material inside the solenoid. The rate of joule heating doesn’t change.