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Magnetism And Matter — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsMagnetism And Matter1 Mark
Question
Two statements are given-one labelled Assertion(A) and the other labelled Reason (R). Select the correct answer to these questions from the codes(a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): A clinic lines on the magnetic map represents lines of equal dip.
Reason (R): When the horizontal and vertical components of the earth's magnetic field are equal, the angle of dip is 60º.
✓

Answer

  1. A is false and R is also false.

Explanation:

The angle of dip is the angle between the axis of the dip needle in the magnetic meridian and the horizontal direction.

$\tan\theta=\frac{\text{Vertical component of the earth's magnetic field}}{\text{Horizontal component of the earth's magnetic field}}$

$=\frac{\text{B}_\text{V}}{\text{B}_\text{H}}$ When, $\text{B}_\text{V}=\text{B}_\text{H},\tan\theta=1\Rightarrow\theta=45^\circ$

Lines joining points of zero dip are called Aclinic lines. Lines joining points of equal dip are called isoclinic lines.

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