$A$ dip circle is at a right angle to the magnetic meridian. What will be the apparent dip in degrees?

At a certain place,the horizontal component of the Earth's magnetic field is $B_0$ and the angle of dip is $45^o$. The total intensity of the Earth's magnetic field at that place will be:

At a certain place,the angle of dip is $30^{\circ}$ and the horizontal component of the Earth's magnetic field is $0.5 \ G$. The Earth's total magnetic field (in $G$) at that place is:

Answer the following questions:
$(a)$ The earth's magnetic field varies from point to point in space. Does it also change with time? If so,on what time scale does it change appreciably?
$(b)$ The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?
$(c)$ The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the 'battery' (i.e.,the source of energy) to sustain these currents?
$(d)$ The earth may have even reversed the direction of its field several times during its history of $4$ to $5$ billion years. How can geologists know about the earth's field in such distant past?
$(e)$ The earth's field departs from its dipole shape substantially at large distances (greater than about $30,000\; km$). What agencies may be responsible for this distortion?
$(f)$ Interstellar space has an extremely weak magnetic field of the order of $10^{-12}\; T$. Can such a weak field be of any significant consequence? Explain.

What is the dynamo effect?

Lines which represent places of constant angle of dip are called