Name: Magnetic Flux
Uploaded: 2019-07-19
Duration: 6 min 44 s
Description: Magnetic flux is the total number of magnetic lines of force that are passing through a given surface. To learn more about this intriguing concept, watch the...

Question

Draw a neat diagram of a tangent galvanometer. Explain how it may be used to measure a current. Why it is most accurate when deflection is near to

45 °

.

Accepted Answer

Tangent galvanometer is an early measuring instrument for small electric currents. It consists of a coil of insulated copper wire wound on a circular non-magnetic frame. Its working is based on the principle of the tangent law of magnetism.

When a current is passed through the circular coil, a magnetic field $(B)$ is produced at the center of the coil in a direction perpendicular to the plane of the coil. It is arranged in such a way that the horizontal component of earth’s magnetic field $(B_{H})$ is in the direction of the plane of the coil. The magnetic needle is then under the action of two mutually perpendicular fields.

If $θ$ is the deflection of the needle, then according to tangent law, $B = B_{H} \tan θ . . . (1)$ .

Let $I$ is the current passing through the coil of radius $a$ with $n$ turns, then the field generated by the current carrying circular coil is, $B = \frac{μ_{0} n I}{2 a} . . . (2)$ .

Equating $(1)$ and $(2)$ , we get,

$B_{H} \tan θ = \frac{μ_{0} n I}{2 a} \Rightarrow \frac{2 a B_{H}}{μ_{0} n} = \frac{I}{\tan θ} = K$ , here $K$ is called the reduction factor.

The horizontal intensity of earth’s magnetic field is $B_{H} = \frac{μ_{0} n K}{2 a}$ .

Now, sensitivity of tangent galvanometer is $S = \frac{θ}{I} = \frac{θ}{K \tan θ} .$

Maximum value of $\tan θ = 1$ $\Rightarrow θ = \tan^{- 1} (1) = 45 °$ .

Hence, it is most accurate when deflection is near to $45 °$ .

Draw a neat diagram of a tangent galvanometer. Explain how it may be used to measure a current. Why it is most accurate when deflection is near to $45 °$ .

Important Questions on Electromagnetism

Learn and Prepare for any exam you want !

Draw a neat diagram of a tangent galvanometer. Explain how it may be used to measure a current. Why it is most accurate when deflection is near to 45°.

Important Questions on Electromagnetism

Learn and Prepare for any exam you want !

Draw a neat diagram of a tangent galvanometer. Explain how it may be used to measure a current. Why it is most accurate when deflection is near to $45 °$ .