Which one of the following statements is not correct?
[amp_mcq option1=”The earth’s magnetic field is due to the motion of metals like iron and nickel in the core of the earth” option2=”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” option3=”If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density decreases” option4=”When the speed of a conductor moving through a magnetic field is increased, the induced voltage increases” correct=”option2″]
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.