Question

For making magnets such as those used in loudspeakers, material should have

• A. high retentivity, high coercivity and large hysteresis loss
• B. low retentivity, low coercivity and low hysteresis loss
• C. high retentivity, low coercivity and low hysteresis loss
• D. high retentivity, high coercivity and low hysteresis loss

Answer 1

The correct option is B low retentivity, low coercivity and low hysteresis loss

The material used in a speaker is an electromagnet. It should have low retentivity, so that it doesn't get magnetized permanently, or gets demagnetised easily after removing current.

Coercivity is the magnetic field intensity needed to reduce the magnetization of a ferromagnetic material from complete saturation to zero. It should have low coercivity .

Hysteresis loss should be small. It should not be heated up during magnetisation and demagnetisation.