Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Nuclear force is :

Which one of the following is the practical unit of power?

Two insulated charged conducting spheres of radii 20 cm and 15 cm respectively and having an equal charge of 10 C  are connected by a copper wire and then they are separated. Then(a) Both the spheres will have the same charge of 10 C (b) Surface charge density on the 20 cm  sphere will be greater than that on the 15 cm  sphere(c) Surface charge density on the 15 cm sphere will be greater than that on the 20 cm  sphere(d) Surface charge density on the two spheres will be equal

Consider a wire carrying a steady current, I placed in a uniform magnetic field B perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do no work. This implies that:

Which among the following is true?

Which of the following statements is incorrect about hysteresis(a) This effect is common to all ferromagnetic substances(b) The hysteresis loop area is proportional to the thermal energy developed per unit volume of the material(c) The hysteresis loop area is independent of the thermal energy developed per unit volume of the material(d) The shape of the hysteresis loop is characteristic of the material

In p-type semiconductors, holes are:

Electromagnets are made of soft iron because soft iron has:

1. High retentivity and high coercive force.
2. High retentivity and low coercive force.
3. Low retentivity and high coercive force.
4. Low retentivity and low coercive force.