What is a post office box in physics?
The post office box was a Wheatstone bridge-style testing device with pegs and spring arms to close electrical circuits and measure properties of the circuit under test.
The best material for resistance in post box resistor is Manganin. It is an alloy of copper (85%), Manganese (12%) and Nickel (2%).
Why the instrument is called post office box?
Description of the instrument It is called a post office box because it was originally used by the postal department for the measurement of the resistance of the telegraph wires and cables.
Post Office Box Physics || Current Electricity Class 12, JEE & NEET - A Post Office Box can also be used to measure an unknown resistance. It is a Wheatstone Bridge with three arms P, Q and R; while the fourth arm(s) is the unknown resistance. P and Q are known as the ratio arms while R is known as the rheostat arm.12-Feb-2020
What is the aim of the post office box experiment?
Post Office Box is helpful in physics experiment to determine the unknown resistance of wires like Constantan and Nichrome etc. With the help of Nvis 6041, the student can learn the principle of Post Office Box and its working. It can determine the specific resistance of different types of wire.
A post box is a numbered box which are available on rent at certain major post offices. Every post box is allocated a number and only postal articles bearing that number are placed into that box.
What is measured by using post office box?
an unknown resistance
This reduces the volume of the letterbox, thus reducing the cost of transportation. This also helps in protecting the plastic top during transit. India Post now plans to replace the old letter boxes with the new ones wherever necessary.
What is the practical utility of the post office box in day to day life?
Answer: By post office we can get our e mail and neccessary things and we can also parcel neccessay information in form of letters, envelops and post cards etc. and then we can give it in an post office with name and address of that person and in few time the postman will deliver it to the address written on it.30-Jul-2020
In a metre bridge experiment, null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4X against Y? A. 50 cm. Right on!
What is the difference between resistance and resistivity?
Resistance is the physical property of a substance because of which it opposes the flow of current i.e. electrons. Resistivity is the physical property of a particular substance which is having particular dimensions.24-Jul-2020
Definition of resistance box : an instrument for measuring and comparing electrical resistances.
What is the principle of Wheatstone bridge?
What is the Wheatstone Bridge Principle? The Wheatstone bridge works on the principle of null deflection, i.e. the ratio of their resistances is equal, and no current flows through the circuit. Under normal conditions, the bridge is in an unbalanced condition where current flows through the galvanometer.
Definition of Wheatstone bridge : an electrical bridge consisting of two branches of a parallel circuit joined by a galvanometer and used for determining the value of an unknown resistance in one of the branches.
What is half deflection method?
The half deflection method is the method by which an internal resistance of a cell can help in evaluating value which is considered as high. The deflection of half is considered as a value obtained along with the cell alone.
Post Office Box, Physics named it so because it has a shape of box and was designed to find resistance of electric cables and telegraph wires. Coils of wire are wound non-inductively, mounted in the body of the box, and have a negligible temperature coefficient. Pairs of ratio arms are each 10, 100, 1000 ohms.07-Feb-2021
Why post boxes are of different Colours?
The reason for having different coloured letterboxes is to differentiate mails meant for different destination at the time of receiving them. This helps in sorting out the mails in quick time and delivery them. Red boxes are meant for mails which are to not to be delivered locally.27-Aug-2019
On 4 July 1955, Postmaster General Arthur Summerfield announced that the Post Office would begin painting all mail collection boxes in red, white, and blue to make them easily identifiable. Subsequently, the Post Office began painting mail collection boxes in red and blue, with white lettering.
What colour were post boxes originally?
The early green painted boxes were unobtrusive, excessively so. Complaints were received by people having difficulty finding them and a return to red was specified in 1874. It took 10 years to complete the programme of re-painting. Red remained the standard colour for boxes from then on with few exceptions.
The primary function of Post Office is collection, processing, transmission and delivery of mail.
What is it used for post office?
A post office is a public facility and a retailer that provides mail services, such as accepting letters and parcels, providing post office boxes, and selling postage stamps, packaging, and stationery.
What is a post office box in physics?