2016 · Q44
Which one of the following statements is not correct?
general-sciencephysics-light-electricity
- AThe earth's magnetic field is due to the motion of metals like iron and nickel in the core of the earth
- BThe 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
- CIf the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density decreases
- DWhen the speed of a conductor moving through a magnetic field is increased, the induced voltage increases
Explanation
Magnetic field lines are most crowded (closest together) near the poles where the field is strongest, and more widely spaced away from the poles; statement (B) asserts the reverse, so it is not correct. The geomagnetic field does arise from motion of iron-nickel in the outer core, flux density does fall when area rises at constant flux, and induced EMF does rise with conductor speed. Hence (B) is the incorrect statement.