Why is silicon not melting?
I’m using a zvs inductive heater to try to melt some 99.85% polycrystalline silicon, as would occur in the Czochralski process, but the silicon workpiece is not melting let alone even getting hot. The silicon workpiece is about the size of a playing dice, and becomes fully conductive after preheating to about 100* C. Even after preheating the workpiece while in the coil to achieve adequate conductivity, the inductive heater still doesn’t “take over” to raise the temperature. The inductive heater works fine with other conductive materials such as iron and aluminum and heats them quite effectively. A Czochralski process patent I came across claims that the silicon must be preheated to at least 1000* C, but many other Czochralski process
diagrams and research papers make no mention of any necessary preheating.
Asked Patrick Underwood
A train is approaching a platform with a speed of 20 km/hr. A bird is sitting on a pole at the platform. When train is 2 km away from the pole brakes are applied so that the train accelerates uniformly, simultaneously the bird also flies towards the train with a velocity 60 km/hr. It touches the nearest point on the train and flies back and back again and so on. find total distance travelled by the bird before train stop.
Can you solve this problem by relative motion concept?
Asked Sandeep Mishra
Do moving charges have both electric and magnetic fields?
The question was asked by Areesha Imtia
A charge always produces an electric field around it.
When the charge moves, it creates a magnetic field too. Since when the charge is moving the electric field varies and cause the production of magnetic field.
I now stay alone doing the cooking and washing all alone. In between cooking also I manage to watch a bit of TV, browse net, respond to WhatsApp and FB etc. Most of the time, I successfully manage alll these without any mishaps. A few days back it so happened that I kept milk for boiling in a steel sauce pan on the induction cooker. A WhatsApp chat engaged me so much that after some time I smelt a burning of vesselt. When I looked, I was shocked to see that the entire milk was boiled and finished and the vessel was all burnt dark like charcoal. I tried to add gel cleaner and scrubber and even after two days most of the charcoal like appearence of the vessel remained and I thought that the vessel may not be put to use anymore.
Suddenly there was a flashing memory, my grandmother seemed to tell, “put some raw rice and water in the vessel, keep for some time and scrub.” Suddenly I decided to try this. A handful of raw rice was put into the burnt vessel and some water was also added. I kept it for about half an hour and then started scrubbing. To my astonishment, the charcoal like coating which I had on the steel vessel, which I thought I will never be able to remove, started to come ouot now. Within a few minutes of rubbuing most of the burnt coating was removed. I was really happy and at the same time felt apprecoative of the ancient techniques of cleaning. In ancient times, when they didn’t have LPG or induction cooker, cooking was mainly by burning wood and getting a cot of carbon over the vessel was common. But every day the vessels were cleaned like sparkling new except the bottom part which is intentionally left black and rough to enable maximum absorption of heat from the source during cooking. The black colour has the piorpert5y of absorbing all the heat radiations incident on it.
Various techniques are used at that time depending on the type of burn or the type of dirt.
For example, If a copper vessel is having black patches, we use tamarind and coconut fibres along with some clean sand. The tamarind reacts with copper oxide and loosens it, the fibre provides a smooth hold and contains the tamarind and sand. The sand which is silica, is hard and acts as the sdcrubbing particles releasing the copper oxide from metal surface. Thus in a few minutes, the copper vessel will shine like new, which is also the result of the lustre of metal. (shining of a freshly cut metal surface. The scrubbing takes away a thin layer of the dim oxidised surfaces and makes it shiny)
Let’s come back to my case, the action of raw rice. Just like the example of cleaning copper vessel, here the rice provides some chemical reaction with the burnt mik and carbon. When the burnt vesssel is allowed to stand for a while with water and rice, the rice gets softened and the rice husk remains get released. The soaked rice reacts with the burnt milk and loosens it. Now after about half an hour when we start scrubbing, the nanosized rice husk particles which are hard like silicate helps in removing the loosened burnt milk.
This action of the hard and smooth nano particles along with the chemical reaction of rice with the burnt milk help to clean the vessel easily.
Most of the Kendriya Vidyalayas across the country are reopening after the summer vacation on 21 June 2018. Now students are returning to studies after 50 days of enjoyment and recharging their intellectual batteries. The rejuvenated spirits will nw help the students to return to studies with greaster exposure they had during the summer vacation, visit to places, new experiences and experimentsd. Each and every experience we come across help us learning something new, no matter whether we were successful in our attempts or not. The one who fails a number of times and finally succeeds learns more life lessons that the one who sucfceed at the first attempt itself. It is not harmful if you win at first attempt, but if you don’t succeed, do not quit. It’s another opportunity to attempt with greater vigour and to try out new methods to succeed.
AskPhysics has some new programs for this year.
- Class XII: Questions asked by students fromstudents related to class XII will be arranged chapterwise for ewasy access.
- More study materials will be made available to class XII and Class X students for a structured learning and revision
- More analogies and life experiences will be added in the form of story like blog entries for making learning of Physics enthusing and entertaining; helping the readers to understand life better through Physics as well as to learn Physics from life incidents.
During a robbery, a citizen was shot in the shoulder. the bullet went through the shoulder and exited; he will make full recovery. there were three suspects present; each one fired their pistol. it is important to determine which suspect actually shot the citizen.
Alan was carrying a .38 special, bill was carrying a .45 colt, cindy was carrying a .357 magnum.
Based on testimony, it can be determined exactly where the citizen was standing when he was shot. the emergency doctor report states that the bullet emerged from the shoulder with a perfect horizontal velocity. ballistics studies show that a bullet slows down to 30% of its initial muzzle velocity.
The bullet left the citizen’s shoulder 1.6325m above the ground. The hole in the wall was centered 1.627m above the ground, and 3 m behind him.
Use the information below to determine who shot the citizen:
Sydney Marina McCage
You may post your answers as comments to this post
EMU local departing at 9:15 AM on its way from hazrat nizamuddin to gaziabad meets with an accident near shibabad at a manless railway crossing. the accident occurred at 9:45 AM when the driver of car tried to cross a railway crossing even when he saw the train coming. The driver of the car died in this accident. Without any delay the train continued for its destination but due to damage in th engine, rest of the journey was travelled at 1/3rd of its usual speed and it reached 2 hours late from its scheduled time even though it didn’t stop anywhere in the rest of its journey” Assuming that it moves with constant speed every day , find the time at which it reaches gaziabad that day?