Question

Draw a labelled diagram of moving coil galvanometer. Describe briefly its principle and working. Answer the following- (i) Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer. (ii) Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving a reason. iii)Explain how will you convert a galvanometer into i)voltmeter ii) ammeter

Answer 1

Answer:

Principle: The underlying principle ofmoving coil galvanometer is that acurrent carrying coil, placed in a uniform magnetic field, experiences torque. b) i) The soft iron coil in a galvanometer will make the field radial. Also, it increases the strength of the magnetic field.

Answer 2

$\huge\bold\pink{\underline{\underline{{ANSWER:}}}}$

✦ Draw a labelled diagram of moving coil galvanometer.

⇝Refer attachment ⬆⬆

✦ Describe briefly its principle and working.

$\bf{\underline\green{PRINCIPLE:}}$

⇝Torque acts on a current-carrying coil suspended in the uniform magnetic field.

⇝Due to this, the coil rotates.

⇝Hence, the deflection in the coil of a moving coil galvanometer is directly proportional to the current flowing in the coil.

$\bf{\underline\green{WORKING:}}$

⇝Let a current I flow through the rectangular coil of n number of turns and a cross-sectional area A.

⇝When this coil is placed in a uniform radial magnetic field B, the coil experiences a torque τ.

⇝When equal and opposite forces F called couple acts on the coil, it produces a torque.

✦ Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer.

⇝The cylindrical soft iron core, when placed inside the coil of a galvanometer, makes the magnetic field stronger and radial in the space between it and pole pieces, such that whatever the position of the rotation of the coil is the magnetic field is always parallel to its plane.

✦ Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving a reason.

⇝Current sensitivity does not depend upon resistance(R), whereas voltage sensitivity does, as evident from their expressions.

⇝Current sensitivity can be increased by increasing the number of turns of the coil.

⇝However, this increases the resistance of the coil also(R is proportional to length of conductor).

⇝Since voltage sensitivity decreases with increase in resistance of the coil, the effect of increase in number of turns is nullified in the case of voltage sensitivity.

⇝Hence, there is no increase in voltage sensitivity.

✦ Explain how will you convert a galvanometer into:-

$\bf{\underline\green{VOLTMETER:}}$

⇝A galvanometer can be converted into voltmeter by connecting a high resistance called multiplier in series to the galvanometer.

⇝This equation gives the value of resistance R, which connected in series to the galvanometer, is converted into a voltmeter of range 0 – V volts.

$\bf{\underline\green{AMMETER:}}$

⇝A galvanometer can detect only small currents. Thus, to measure large currents it is converted into an ammeter.

⇝It can be converted into an ammeter by connecting a low resistance called shunt resistance in parallel to the galvanometer.

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