Electrostatics — Physics STD 12 Science — Question

Which of the following is / are true about the principle of Van de Graaff generator?

The molecules in which centres of positive and negative charges coincide are called as:

Lightning is a ________ phenomenon:

The optical density of turpentine is higher than that of water while its mass density is lower. Fig. shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in Fig, the path shown is correct?

Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough the object looks distorted because:

A single slit of width a is illuminated by violet light of wavelength 400 nm and the width of the diffraction pattern is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 600 nm, the width of the diffraction pattern is(a) The pattern vanishes and the width is zero(b) y / 3(c) 3y(d) None of these

For a metallic wire, the ratio V/i   (V =  the applied potential difference, i = current flowing) is(a) Independent of temperature(b) Increases as the temperature rises(c) Decreases as the temperature rises(d) Increases or decreases as temperature rises, depending upon the metal

The part of a transistor which is heavily doped to produce a large number of majority carriers, is(a) Base(b) Emitter(c) Collector(d) None of these