Magnetic Effects of Electric Current — Science STD 10 — Question

Choose the incorrect statement from the following regarding magnetic lines of field:

1. The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points.
2. Magnetic field lines are closed curves.
3. If magnetic field lines are parallel and equidistant, they represent zero field strength.
4. Relative strength of magnetic field is shown by the degree of closeness of the field lines.

Which of the following controls the amount of light entering the eye?

1. Ciliary muscles.
2. Lens.
3. Iris.
4. Cornea.

he insulator of electricity is:

A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances R₁, R₂ and R₃ respectively (Figure). Which of the following is true?

Which of the following can make a parallel beam of light when light from a point source is incident on it?

The focal length of concave lens required to correct myopia is:

A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

When light rays enter the eye, most of the refraction occurs at the.

The essential difference between an AC generator and a DC generator is that:

1. AC generator has an electromagnet while a DC generator has permanent magnet.
2. C generator will generate a higher voltage.
3. AC generator will generate a higher voltage.
4. AC generator has slip rings while the DC generator has a commutator.

Which one of the following substances are used to make electric switches and switch boards: