What is soft iron core??
Answers
Answer:
iron that has a low carbon content and is easily magnetized and demagnetized with a small hysteresis loss. (as modifier)a soft-iron core
Explanation:
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A moving coil meter is a very common form of analog voltmeter because of its sensitivity, accuracy, and linear scale, although it only responds to DC signals. it consists of a rectangular coil wound round a soft iron core that is suspended in the field of a permanent magnet. The signal being measured is applied to the coil and this produces a radial magnetic field. Interaction between this induced field and the field produced by the permanent magnet causes a torque, which results in rotation of the coil. The amount of rotation of the coil is measured by attaching a pointer to it that moves past a graduated scale.
where B is the flux density of the radial field, I is the current flowing in the coil, h is the height of the coil, w is the width of the coil, and N is the number of turns in the coil. If the iron core is cylindrical and the air gap between the coil and pole faces of the permanent magnet is uniform, then the flux density B is constant i.e., the torque is proportional to the coil current and the instrument scale is linear.
The torque due to the coil current is opposed by the reaction torque of a torsional spring such that the final rotational displacement of the coil is proportional to the measured current.
As the basic instrument operates at low current levels of 1 mA or so, it is only suitable for measuring voltages up to around 2 V. If there is a requirement to measure higher voltages, the measuring range of the instrument can be increased by placing a resistance in series with the coil, such that only a known proportion of the applied voltage is measured by the meter. In this situation, the added resistance is known as a shunting resistor.
These materials produce a substantially greater flux density, which, besides allowing the magnet to be smaller, has additional advantages in allowing reductions to be made in the size of the coil and in increasing the usable range of deflection of the coil to about 120°. Some versions of the instrument also have either a specially shaped core or specially shaped magnet pole-faces to cater for special situations where a nonlinear scale such as a logarithmic one is required.