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Class XII Helpdesk for Pre-Board Exam dated 17.01.14

Q-what is meant by chemical formula?
Asked By:jaspinkle singh
Time:1/15/2014 (19:38:36)
Response: The chemical formula is a way of expressing the amount of atoms that make up a particular compound. For example water is comosed of 2 hydrogen atoms and one oxygen atom. Therefore, water's chemical formula is H2O
Response by:Muskan billa (Author: quaddomaths, quaddoscience, quaddhelp)

Q2. what do we mean by copyright ? what does it mean ?
Topic: Explain Copyright (FIT)
Asked by: Mandeep Singh
Time: 1/11/2014 23:04:22

Response: Copyright is a legal term used to describe the rights that creators have over their literary and artistic works. Works covered by copyright range from books, music, paintings, sculpture and films, to computer programs, databases, advertisements, maps and technical drawings. Read more on wipo.int

Q3.What is persistance of vision?
Topic:The human eye and the colourful world
Asked by:Karan Ohri
Time:1/16/14 20:08:54

Response:The persistance of vision is an ability of eye to persist an image on retina for one sixteenth of a second even when the object is removed away from the front of the eye.
This is due to a prolonged chemical reaction. As a result, the eye cannot clearly distinguish fast changes in light that occur in front of it.
This visual perception of the eye is used in making videos.

Response by: Tanjotveer Kaur

Q4.XML vs HTML;comments in xml;hacker vs cracker;data backup and online backup?
Topic:xml,html,societal impacts
  Asked by: AMRIT SINGH
  Time:1/16/14 18:11:44

Response:
html vs xml
-HTML is for displaying data and xml is for transporting data.
-Closing tags are not mandatory in HTML but they are mandatory in xml.
-HTML is static and xml is dynamic.
comments in html are in our syllabus
two ways-

first-

second-<comment> </comment>

HACKERS VS CRACKERS

Actually hackers are of two types

first,white hat hackers or simply hackers

second,black hat hackers or crackers

A hacker is a person intensely interested in the workings of any computer operating system. Hackers are most often programmers. As such, hackers obtain advanced knowledge of operating systems and programming languages. They might discover holes within systems and the reasons for such holes. Hackers constantly seek further knowledge, freely share what they have discovered, and never intentionally damage data.
A cracker is one who breaks into or otherwise violates the system integrity of remote machines with malicious intent. Having gained unauthorized access, crackers destroy vital data, deny legitimate users service, or cause problems for their targets. Crackers can easily be identified because their actions are malicious.

so..all crackers are hackers but all crackers are not hackers.
BACKUP
This is a way to protect your data in which your data is kept at multiple locations.It is to keep your data in the secondary drive other than the original drive.
ONLINE BACKUPS

Type of backups in which the data is saved on the nearby servers from your hard drive using a network connection. The reason for acquiring online backup is simple. By backing up data continuously (or as frequently as needed) on a remote hard drive, the risk of data loss as a result of file corruption, fire, theft, or other natural disasters is practically eliminated. You can safely access or restore any lost files by using any PC with high-speed Internet connection and a Web browser interface. Privacy and security are assured with encryption and password protection.

(hackers vs crackers-source- searchenterprisedesktop.techtarget.com)
(backup-source-www.onlinebackupreviews.com)
Response by: Tanjotveer Kaur

Q5. How to calculate value of sin 120?
Topic: Sin 120

Asked by: Gurpreet Singh

Time: 1/15/2014 21:15:04

Response: Sin 120 = Sin(2x60)
= 2 Sin 60 Cos 60
= 2 (sqrt3/2 x 1/2)
= sqrt3/2 ans

Response by: Aashna Verma

Q6.Why is the colour of sun red in morning and white in noon?
Topic:ATMOSPHERIC REFRACTION
Asked by: AMRIT SINGH
Time:1/23/2014 17:12:45

Response:There are seven colours of white light.We call that pattern of colours as VIBGYOR.The scattering of light is inversely proportional to the wavelength of that light.Violet has the least wavelength,hence scatters the most and red has the longest wavelength,hence scatters the least.So from V to R there is decreasing order of wavelength.
During sunrise or sunset the white light travels longer distance and most of the blue colour gets scattered out of the white light,so the sun appears to be red as red colour scatters the least.
During noon,the distance which sunlight has to travel is less and there are very less particles in air which can scatter the light coming from the sun,so there is less scattering of light and hence the sun appears to be white.
Response by: Tanjotveer Kaur

Q7. Explain the process of re-generation in planaria ?

Topic:regeneration in planaria

Asked by:Himanshu

Time: 1/12/2014 18:57:o3

Response:Planaria is a flatworm found in fresshwater and slow moving streams. planaria posses great power of regeneration . if the body of planaria somehow gets cut into number of peices, then each body peice can regenerate into a complete planaria by growing all the missing parts...(as shown in the given figure.)..

Response by:Ramandeep kaur

Q8.How the number of chromosomes of the sexually reproducing parents & offspring is the same? ?

Topic:How do Organisms reproduce??

Asked by:Vanshdeep Singh

Time: 1/12/2014 18:03:28

Response:Actually they are not same they are single and different in each parent.Every child receives 2 sets of 23 from his/her parents. One set from mom and one from dad ~ a 50/50 split, equaling a total of 46.

Response by:Ramandeep kaur
Q1. why Do mainly Stars Change Their Original Place when we look up in the night ?
Topic: From light and Reflaction (SCIENCE)

Asked by: Rahul kumar

Time: 1/12/2014 14:57:32

Response: Actually the stars don't change their positions,they seem to be changing because of refraction.Stars are far away,look small and are a point source of light and the light coming from them is affected by atmospheric refraction.But if you take the case of objects closer to earth then they are closer than stars.For us they are not a point source.Infact they are collection of point sources and seem to be bigger.The ray of light coming from such object ,if suffers from more refraction then, the intensity of that ray of light decreases but the other ray of light which has suffered less refraction has less effect on its intensity.Likewise,if intensity decreases from one point then it increases at the other point.So they don't seem to change their position.So,mainly stars seem to be changing their positions.

Response by: Tanjotveer Kaur (Author: quaddomaths, quaddoscience, quaddhelp)

We apologize our readers for delay in response. We are trying hard to stand against odds and provide our readers free access to knowledge. Thank you for your patience and Keep Asking as asking is the way to knowledge.

#include<iostream>

using namespace std;

class tv
{

int channel,volume;
int on;
int get_channel()
{
channel=1;
return channel;
}

int get_vol()
{
volume=1;
return volume;
}

public:

tv()
{
channel=get_channel();
volume=get_vol();
cout<<"\n current channel is : "<<channel<<" and volume is : "<<volume;
}

void turn_on()
{
on=1;
}

void turn_off()
{
on=0;
}

void set_channel(int m)
{
channel=m;
cout<<"\n Current channel is"<<channel;
}

void set_volume (int n)
{
volume =n;
cout<<"\n current volume is"<<volume;
}

void channel_up()
{
channel+=1;
cout<<"\n current channel is"<<channel;
}

void channel_down()
{
channel-=1;
cout<<"\n current channel is"<<channel;
}

void vol_up()
{
volume+=1;
cout<<"\n current volume is"<<volume;
}

void vol_down()
{
volume-=1;
cout<<"\n current volume is"<<volume;
}
};

void main()
{
int x,y,z;
tv t1;

do
{
cout<<"do you want to make any changes (1/0)";
cin>>x;
if (x == 1)
{
cout<<"1. turn off \n 2.turn on \n 3. channel up \n 4. channel down \n 5.set channel \n 6.volume up \n 7.volume down \n 8.set volume \n";
cout<<"enter the number ";
cin>>y;
if (y==1)
{
t1.turn_off();
break;
}

switch (y)
{
case 2:
t1.turn_on();
break;
case 3:
t1.channel_up();
break;
case 4:
t1.channeldown();
break;
case 5:
{
cout<<"\n enter the channel no (1-120)";
cin>>z;
t1.set_channel(z);
}
break;
case 6:
t1.vol_up();
break;
case 7:
t1.vol_down();
break;
case 8:
{
cout<<"\n enter the volume level(1-7)";
cin>>z;
t1.set_volume(z);}
break;
}
}
}
while(x== 1);
cout<<"thank you";
}

Subject	Page Number
ENGLISH (CORE) (Code No. 301)	74
MATHEMATICS (Code No. 041)	104
PHYSICS (Code No. 042)	115
CHEMISTRY (Code No. 043)	134
BIOLOGY (Code No. 044)	153
COMPUTER SCIENCE (Code No. 083)	208
INFORMATICS PRACTICES (Code No. 065)	223
MULTIMEDIA AND WEB TECHNOLOGY (Code No. 067)	235
ECONOMICS (Code No. 030)	250
BUSINESS STUDIES (Code No. 054)	259
ACCOUNTANCY (Code No. 055)	291
PHYSICAL EDUCATION(Code No. 048)	401

Subject	Page Number
HINDI COURSE - B (Code No. 085)	71
ENGLISH-COMMUNICATIVE (Code No. 101)	90
MATHEMATICS (CODE NO. 041)	126
SCIENCE (Code No. 086 / 090)	138
SOCIAL SCIENCE (CODE NO. 087)	150
FOUNDATION OF INFORMATION TECHNOLOGY (CODE No. 165)	257
PUNJABI (Code No. 004)	282 (DOWNLOAD)

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