## Posts

### Difference between Potentiometer and Voltmeter

There are the following differences between a potentiometer and a voltmeter given below: Potentiometer: 1.) It is based on null method. 2.) It gives an accurate value of emf. 3.) While measuring emf, it does not draw any current from the cell. 4.) Resistance of potentiometer wire becomes infinite while measuring emf. 5.) It can be used for various experimental purposes. 6.) It can not be taken conveniently from one place to another place. Voltmeter: 1.) It is based on the deflection method. 2.) It does not give an accurate value of emf. 3.) While measuring emf, it draws some current from the cell. Hence it reads slightly less than the actual emf. 4.) The resistance of the voltmeter is high enough but not infinite. 5.) It can be used to measure potential differences only. 6.) It can be conveniently taken from one place to another place.

### Principle Construction, Working and Angular Magnification of Simple Microscope

Principle of Simple Microscope: The principle of the simple microscope is based on the magnification of an image by using a simple convex lens. Construction: A simple microscope consists of one convergent lens only. The object is placed between the lens and its focal length, and the eye is placed just behind the lens. Then the eye sees a magnified, erect, and virtual image on the same side as the object at the least distance of distinct vision $(D)$ from the eye, and the image is then seen most distinctly. Working: If the small object $ab$ is placed between a lens $O$ and its first focus $f$ then Its magnified virtual image $a_{1}b_{1}$ is formed at a distance $D$ from the lens. Since the eye is just behind the lens, the distance of image $a_{1}b_{1}$ from the eye is also $D$. Angular Magnification Or Magnifying Power($M$): The ratio of the angle subtended by the image at the eye ($\beta$) to the angle subtended by the object at the eye when placed at

### Light and its properties

The basic definition of Light: Light is a form of energy that produces the sensation of vision in the eye by which we can see objects. There are some facts about light as follows: 1. Lightwave moves along a straight line path. 2. Light waves can travel through vacuum and medium both. 3. Light is an electromagnetic wave. 4. A light wave is the transverse wave in nature. 5. Light can be dispersed. Besides these facts, light also shows the phenomenon of interference, diffraction, polarisation photoelectric effect, etc. To explain the above facts, many principles have been given from time to time, e.g., Newton's corpuscular theory, Huygen wave theory, Maxwell's principle of electromagnetic wave, Planck's quantum principle, dual nature of light, etc.

### Origin of Biomedical Signals

The biomedical signals differ from other signals only in terms of the application — signals that are used in the biomedical field. As such, biomedical signals are produced from a variety of sources. The following is a brief description of these sources: 1. Bioelectric signals:  The bioelectric signal is unique to biomedical systems. It is produced by nerve cells and muscle cells. It is produced due to the membrane potential, which under certain conditions may be excited to generate an action potential. In single-cell measurements, the specific microelectrodes are used as sensors, and the action potential itself is considered as the biomedical signal. In more gross measurements, the surface electrodes are used as sensors, and the electric field generated by the action of many cells, distributed in the electrode’s vicinity, constitutes the bioelectric signal. Bioelectric signals are probably the foremost biosignals. The fact that most biosystems use excitable cells makes it possible,

### Principle Construction, Working and Angular Magnification of Compound Microscope

Principle: The principle of the compound microscope is based on the magnification of an image by using two lenses. Construction: A compound microscope consists of two convergent lenses (i.e. objective lens $O$ and eye-piece lens $e$) placed coaxially in a double tube system. The objective lens is an achromatic convergent lens system of short focal length and short aperture. The other eye-piece lens $e$ is also an achromatic convergent lens system of large focal length and large aperture. The observation is taken through the eye-piece lens by the observer. The eye-piece lens is fitted outer side of a movable tube and the inner side connects with a non-movable tube in which the objective lens is fitted on another side of the non-movable tube. The separation between the objective or eye-piece lens can be changed by an arrangement, this is known as rack and pinion arrangement. Working: Suppose a small object $ab$ is placed slightly away from the first focus $f_{\circ}$ of the obj

### Applications of Nanotechnology

Nanotechnology has found wide-ranging applications in many fields. There are following some of the important applications discussed below. 1) Electronics: Nanosized electronic components show unique properties which are different from the larger semiconductor components. The semiconductor devices are based on the concept of charge transport only whereas the nanosized components work on the concept of charge as well as spin transport of electrons. This has been used in devices like spin FET, Spin LED etc. These devices have increased the data storage capacities of hard disks and have led to small and faster microprocessors. 2) Energy: Attempts are being made to increase the efficiency of solar cells by using nanotechnology. Another important area of research is the use of hydrogen as a fuel. The main problem with hydrogen is that it is highly combustible and hence cannot be stored easily. Efforts are being made to use carbon nanotubes to trap and store hydrogen. Nanoparticles ar

### Nanoparticles and Its Properties

Introduction: The prefix 'nano' means a billionth ($10^{-9}$). The field of nanotechnology is the study of various structures of matter having dimensions of the order of a billionth of a meter. These particles are called nanoparticles. Nanotechnology is based on the fact that particles that are smaller than about $100 nm$ give rise to new properties of nanostructures built from them. Particles that are smaller than the characteristic length for a particular phenomenon show different physical and chemical properties than particles of larger sizes. For example, mechanical properties, optical properties, conductivity, melting point, and reactivity have all been observed to change when particles become smaller than the characteristic length. Gold and silver nanoparticles were used in window glass panes to obtain a variety of beautiful colors. Nanotechnology has a wide range of applications like producing lighter but stronger materials, constructing faster switches for comput