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Magnetism And Matter

Question
CBSEENPH12037823
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A tangent galvanometer is set with its plane making an angle of 30° with the magnetic meridian. When a current is passed through 2 turns coil of radius 0.10 m, in the anti-clockwise direction, the compass needle shows a deflection of 30°. Calculate the strength of current passed. Take H = 0.32 x 10–4 T.

Solution

Number of turns, N = 2
Radius of the coil, r = 0.10 m
Deflection, θ = 30o 
H = 0.32 × 10-4 T 

Before passing current, compass needle was along the direction of H.
On passing current, the needle shows a deflection of 30° (with H) under the combined effect of H and B.
Magnetic field due to current is in a direction perpendicular to the plane of the coil. 

As compass needle is inclined equally to H and B, as in fig.  



Therefore,
                B = H 

         μ0 N I2r = H 

                  I=2r Hμ0 N  = 2×0.1×0.32×10-44π×10-7×2  

                  I = 2.54 A 


Some More Questions From Magnetism and Matter Chapter

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Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different directions. How is such a thing possible at all?

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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?

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The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

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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?

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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?

Answer the following question:
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?

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