Which one of the following statements is not correct?
The earth’s magnetic field is due to the motion of metals like iron and nickel in the core of the earth
The magnetic field lines of force are widely separated near the poles of a magnet but these lines come closer to one another at other places
If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density decreases
When the speed of a conductor moving through a magnetic field is increased, the induced voltage increases
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CAPF – 2016
Statement C is correct: Magnetic flux density (B) is defined as the magnetic flux (Φ) passing through a unit area (A) perpendicular to the direction of the flux (B = Φ/A). If the flux remains constant but the area increases, the flux density decreases.
Statement D is correct: According to Faraday’s law of electromagnetic induction, the magnitude of the induced voltage (EMF) in a conductor moving through a magnetic field is proportional to the speed at which the conductor cuts the magnetic field lines. Thus, if the speed of the conductor is increased, the induced voltage increases.