Question
Why does a phonograph-record attract dust particles just after it is cleaned?
✓
Answer
When a phonograph record is cleaned, it develops a charge on its surface due to rubbing. This charge attracts the neutral dust particles due to induction.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A parallel beam of monochromatic light is used in a Young's double slit experiment. The slits are separated by a distance d and the screen is placed parallel to the plane of the slits. Show that if the incident beam makes an angle $\theta=\sin^{-1}\Big(\frac{\lambda}{2\text{D}}\Big)$ with the normal to the plane of the slits, there will be a dark fringe at the centre $P_0 $ of the pattern.
→Two conducting spheres of radii $R_1$ and $R_2$ are kept widely separated from each other. What are their individual capacitances? If the spheres are connected by a metal wire, what will be the capacitance of the combination? Think in terms of series$-$parallel connections.
→Figure, shows two coherent sources $S_1$ and $S_2$ which emit sound of wavelength $\lambda$ in phase. The separation between the sources is $3\lambda.$ A circular wire of large radius is placed in such a way that $S_1S_2$ lies in its plane and the middle point of $S_1S_2$ is at the centre of the wire. Find the angular positions $\theta$ on the wire for which constructive interference takes place.
→Identify the electromagnetic waves whose wavelengths vary as :
(a) $10^{-12} m<\lambda<10^{-8}m$ (b) $10^{-3} m<\lambda<10^{-1}m$
Write one use of each.
→(a) $10^{-12} m<\lambda<10^{-8}m$ (b) $10^{-3} m<\lambda<10^{-1}m$
Write one use of each.
What is conductivity ? On which what factors does it depend and also write its unit and dimension.
A plate of thickness t made of a material of refractive index $\mu$ is placed in front of one of the slits in a double slit experiment.
→- Find the change in the optical path due to introduction of the plate.
- What should be the minimum thickness t which will make the intensity at the centre of the fringe pattern zero? Wavelength of the light used is $\lambda$. Neglect any absorption of light in the plate.
Does a body at $20^\circ C$ radiate in a room, where the room temperature is $30^\circ C$? If yes, why does its temperature not fall further?
→A Galilean telescope is $27\ cm$ long when focused to form an image at infinity. If the objective has a focal length of $30\ cm,$ what is the focal length of the eyepiece?
→A potential difference $V$ is applied across the ends of a conductor of length $L$ and diameter $D$. What will be the effect on drift velocity of charge carriers in the conductor when (i) V is made half (ii) L is doubled and (iii) D is made half?
→A hydrogen atom in a state having a binding energy of 0.85eV makes transition to a state with excitation energy 10.2eV (a) Identify the quantum numbers n of the upper and the lower energy states involved in the transition. (b) Find the wavelength of the emitted radiation.