Acer Laptop Repair Services

We offer a wide range of repair services, whether it is to replace your broken laptop screen, upgrade your machine or to help you setup your new laptop in the comfort of your own home or office, we are always able to lend a hand. Even if you are unsure of what your computer needs – no problem, the chances are we can still help.

Our high-quality of services, fast turnaround and low prices has helped us win awards – so you can be rest assured that if we are unable to fix your computer, there is a chance that no one else can.

Problems encountered by laptops:

 
Broken Laptop Screen Repair
If the screen of your laptop is broken, give us a call! Information regarding your laptop will be obtained and we will give you an estimated cost and time it takes to repair your laptop.

Motherboard Repair
When your laptop cannot be switched on, auto-offs or overheats, it is often due to the motherboard or the chipset being broken. Our services help by changing the chipset on the motherboard to a new one.

USB / Headphone Jack Repair
Jacks are the holes on the laptop where various cables can be plugged into. If the cables were to be removed, the ports can stop working or short out. Water and other external factors can spoil the USB and headphone jacks. On a laptop, these are often integrated into the motherboard and are hard to replace.

Power Jack Repair
There are numerous ways the power jack can be damaged. The most common way is when your power cord is suddenly pulled out. This affects both the power cord as well as the jack on the laptop. Continuous usage of a damaged power cord corrupts the laptop and pose as an electrical hazard as well.

Broken Keyboard Keys
Laptop keys break off very easily. Whether something’s been dropped on the keyboard or your kids have forcibly torn them off, you want your keyboard to go back to being perfect as possible.

Battery Life Improvements
We consider the methods to carry out based on the type of laptop you have and configure the system to run at its best as long as possible.

We serve all major brands including:

 

Acer Computer & Laptop Repair

HP Printer Repair, Service and Maintenance Agreements

Your business uses HP laser printers, business-class inkjet printers and multi-function devices because you demand quality, reliability and performance. That’s why you need a trusted and reliable source for HP service.

#1 HP Printer Service Center in the Dubai
General Data is the #1 HP Service Center used by companies throughout the Dubai. We provide HP repair services and HP maintenance contracts for all types of Hewlett-Packard business-class devices, including mono and color laser printers, business-class inkjet printers and multi-function devices.
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Printer Repair Services — international Educational Group

Printer Repair Services Printer is a UAE company known for making extensive range of printers for household and business customers. Using the latest technology it makes useful printers like dot matrix, inkjet, Laser Jet and wireless technology based printers and scanners. But the advance technology can never protect printers from falling into the technical glitches…

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HP Error Codes

HP LaserJet Printer Error Codes

If your HP LaserJet printer has stopped working then it will probably also display an error message. These error messages are there to help you troubleshoot and repair yours LaserJet’s fault. Different models have slightly different wording for the error, but the troubleshooting tips are generally the same.

Common HP Printer Error Messages

Many HP printer error messages are common amongst the range, both old and new. Many, such as 11 – Paper Out, may seem fairly self-explanatory but could actually be the result of something else. Here’s our quick guide to the most common HP printer error codes, what the error codes mean and how to fix them.

HP Error Code:

02 – Warming Up

Explanation:

This is commonly associated with printer cable or driver problems.

What to do:

Turn off the printer and remove the printer cable (USB or I/O cable), then turn it back on. If the printer reports “Ready” then first update the driver, and if not resolved then the printer cable. If there is still an error, there may be a hardware problem.

HP Error Code:

10 – Supplies Memory Error

Explanation:

Your printer has a problem with the toner cartridge chip, which it’s unable to read. This is the electronic information, or e-label, on the print cartridge.

What to do:

First of all try resetting the printer by turning it on and off. If this doesn’t work remove and reinstall the cartridge or replace it. If is still doesn’t work then you may have a hardware fault.

HP Error Code:

11 – Paper Out

Explanation:

If your printer isn’t out of paper, this probably means there’s a problem with the paper tray or paper sensor.

What to do:

Make sure your printer is on a completely flat surface. Check the paper trays for any damage and clean away any toner build up. If not resolved, check the paper sensor or clean the opto-sensor.

HP Error Code:

12 – Open or No EP

Explanation:

If you printer does have toner cartridges installed correctly, this means either a cover is open or you may have defective cooling fans or PS5 sensors.

What to do:

Check the all toners are installed correctly and that all covers are closed properly. If the problem persists you may have a hardware problem.

HP Error Code:

13 – Paper Jam

Explanation:

Your printer has a paper jam. Paper jams can occur at four stages: pickup, printing, fusing and exit. Modern HP printers will indicate where the jam has occurred. If using thick paper, check the HP paper guide for your printer.

What to do:

Either follow the on screen guidance, if available, or methodically check for the paper jam in the customer accessible areas of the printer. Don’t attempt to use hard implements to remove paper at the risk of damage to the printer and yourself. If the problem persists you may have a hardware failure.

HP Error Code:

14 – No EP Cartridge

Explanation:

Your printer either doesn’t have a toner cartridge installed or doesn’t recognise one that is.

What to do:

Removing and reinstalling the toner cartridge normally resolves the problem.

HP Error Code:

16 – Toner Low

Explanation:

This normally means that your toner cartridge is either low on toner or empty. However it may mean that the remaining printer toner isn’t distributed evenly.

What to do:

Try removing the toner cartridge and gently shaking it to evenly distribute the remaining toner. Once depleted, replace the cartridge.

HP Error Code:

20 – Memory Overflow

Explanation:

Your print job exceeds the current memory capacity of the printer.

What to do:

You need to reduce the size of your print job. You can try reducing the DPI or unticking the collate option in the printer driver. You can also try making the document or image more simple. Alternatively you can install additional memory if available.

HP Error Code:

21 – Print Overrun

Explanation:

Your print job exceeds the current memory capacity of the printer.

What to do:

You need to reduce the size of your print job. You can try reducing the DPI or unticking the collate option in the printer driver. You can also try making the document or image more simple. Alternatively you can install additional memory of available.

HP Error Code:

22 – I/O Configuration

Explanation:

There’s a communication problem between the printer and the computer.

What to do:

Where possible, try connecting to a different port on the computer. Try another cable and make sure the computer is turned on and the cable is fully inserted at both ends. If this doesn’t help there may be a hardware issue.

HP Error Code:

24 – Job Memory Full

Explanation:

Too many print jobs have been send to the printer, or the job is too complex for the printer memory to process.

What to do:

You need to reduce the size of your print job. You can try reducing the DPI or unticking the collate option in the printer driver. You can also try making the document or image more simple. Alternatively you can install additional memory if available.

HP Error Code:

25 – XXX Memory Full

Explanation:

Too many print jobs have been send to the printer, or job is too complex for the printer memory to process.

What to do:

You need to reduce the size of your print job. You can try reducing the DPI or unticking the collate option in the printer driver. You can also try making the document or image more simple. Alternatively you can install additional memory if available.

HP Error Code:

30 – PS Error 16

Explanation:

This is commonly associated with PostScript firmware errors. It may also be triggered by PCL files being sent while the print is in PS mode or a bad PostScript file.

What to do:

Reseat the PostScript SIMM or replace it. Try printing an alternative PostScript file to rule out a bad file.

HP Error Code:

30.1.1 – Disk Failure

Explanation:

Your printer’s hard disk drive has crashed.

What to do:

You can normally resolve this by pressing the SELECT button. If it persists you may have a hardware problem.

HP Error Code:

40 – Data Transfer Error

Explanation:

The connection between the computer and printer has been broken.

What to do:

Check/replace all cables as required. Ensure that any EIO boards are seated properly. If networked, check to ensure the IP settings in the printer and driver haven’t changed and match. You can sometimes press SELECT to continue printing however print data may be lost; simply reprint the missing pages.

HP Error Code:

41 – Temporary Print Engine Error

Explanation:

The printer has experienced a temporary printer engine error, which can normally be easily resolved.

What to do:

Turn the printer off at the machine, then the mains and leave for 30 seconds. Turn back on and resend the print job if necessary.

HP Error Code:

49 – Printer Error or Communication Error

Explanation:

There can be a few causes of this error depending on the model, which tend to be associated with firmware errors, cable problems or hardware issues.

What to do:

First try turning the print off and on again. If the problem persists try updating the firmware and replacing the printer communication cables or reseating memory modules. If unresolved then it is most likely a hardware problem.

HP Error Code:

50.x – Fuser Error

Explanation:

The printer fuser is faulty or the supporting circuits or power are at fault. The additional 50.x number indicates:
50.1 Low temperature. Fuser is failing to warm up.
50.2 Warm up failure. The warm-up period timed out. This could be a power supply or firmware issue.
50.3 High temperature. The main thermistor is too hot. Likely to be a control circuit issue.
50.4 Faulty fuser (or Bad AC line voltage). Moderately likely to be bad mains supply (UPS, generator, extensions)
50.5 Inconsistent fuser or Wrong type fuser installed. The printer has detected the wrong fuser.
50.6 Open fuser. Fuser heater cut-off. The fuser possibly overheated.
50.7 Fuser pressure release mechanism failure. Fuser drive motor or the pressure release doesn’t work
50.8 Lower fuser temperature (sub-thermistor). Secondary thermistor detects a fault
50.9 High fuser temperature (sub-thermistor).

What to do:

These faults typically needed assistance from an experienced HP engineer.

HP Error Code:

51 – Beam Detect Error

Explanation:

On older model this normally indicates the tab on the bottom of the cartridge that opens the laser shutter is missing/snapped off. On new models it can be a problem with the whole laser scanner unit.

What to do:

If it’s an older printer then check to see if the tab is missing and if so replace the toner cartridge. New models may need the laser scanner assembly replacing.

HP Error Code:

52 – Incorrect Scanner Speed Error

Explanation:

The printer uses a polygon mirror to reflect the laser beam across the imaging unit. This error code and HP error codes 52.1 and 52.2 indicate a problem with this process.

What to do:

These faults typically needed assistance from an experienced HP engineer.

HP Error Code:

54 – Printer Error Cycle Power

Explanation:

There are many causes for this error code. On some models it means the sealing tape hasn’t been removed from the toner cartridge, which is easily resolved.

What to do:

Check whether tape has been left on the printer cartridges and remove it, if not then this error code typically requires assistant from a HP engineer.

HP Error Code:

55 – Internal Communication Problem / Controller Error

Explanation:

Most likely a poor connection between the DC controller and the formatter. Either or both may have a fault, although this can sometimes be attributed to a faulty fusers, laser assemblies, firmware DIMMS or driver problems.

What to do:

These faults typically needed assistance from an experienced HP engineer.

HP Error Code:

56 – Printer Device Error

Explanation:

This error message can relate to a number of different issues depending upon the model.

What to do:

Try one or more of the following, depending upon your HP printer:
1. Make sure all paper trays are correctly installed
2. Reinstall the stacker or staple/stacker
3. You may be trying to incorrectly print transparencies through the duplex unit
4. You may be trying to print envelopes whilst in duplex mode
5. Check the printer’s configuration to ensure it is correct
6. Turn the print off for 30 seconds and turn on again

HP Error Code:

57.xx – Fan Failure / Gears Seized / Memory Card Error

Explanation:

On modern HP printers this code indicates a failure of one or more fans, on older machines gears seized or memory problems.

What to do:

These faults typically needed assistance from an experienced HP engineer.

HP Error Code:

58.xx Error

Explanation:

There are many causes for this error code, depending upon the model it can mean: environmental sensor error, memory controller problem, fan problem, power problem or DC controller fault.

What to do:

These faults typically needed assistance from an experienced HP engineer.

HP Error Code:

59 – Motor Error

Explanation:

The printer has a motor error, possibly relating to the main motor, fuser motor, image drum motor or ETC motor. On older models HP error code 59 relates to memory problems.

What to do:

If you have an older model then reseating or changing the memory may resolve the issue. All new models typically require assistance from an experienced HP engineer.

HP Error Code:

60.xx –

Explanation:

On new printers this relates to a motorised tray lift error. On older models HP error code 60 relates to memory problems.

What to do:

If you have an older model then reseating or changing the memory may resolve the issue. All new models with tray lift problems can often be resolved by checking for obstructions such as paperclips or other objects.

HP Error Code:

61 – Formatter , Memory Error

Explanation:

Your printer either has improperly fitted or bad memory SIMMs or a defective formatter board.

What to do:

Try simply reseating the memory chips. If this doesn’t work and replacing the chips still doesn’t resolve the problem then you may have to replace the formatter board.

HP Error Code:

62 – Memory Error, Defective Formatter Board

Explanation:

Your printer either has improperly fitted or bad memory SIMMs or a defective formatter board.

What to do:

Try simply reseating the memory chips. If this doesn’t work and replacing the chips still doesn’t resolve the problem then you may have to replace the formatter board.

HP Error Code:

63 – Defective Formatter Board

Explanation:

Your printer either has improperly fitted or bad memory Simms or a defective formatter board.

What to do:

Try simply reseating the memory chips. If this doesn’t work and replacing the chips still doesn’t resolve the problem then you may have to replace the formatter board.

HP Error Code:

64 – Scan Buffer Error

Explanation:

Depending up your model this can be a number of different things including: defective D.C. controller, improperly fitted or bad firmware DIMMs or defective formatter board.

What to do:

Turn the printer off at the machine, then the mains and leave for 30 seconds. If the error code still shows, try reseating the DIMMs and formatter board. If this doesn’t solve the problem then replace the DIMMs and then the formatter board.

HP Error Code:

65 – Scan Buffer Error

Explanation:

Depending up your model this can be a number of different things including: defective D.C. controller, improperly fitted or bad firmware dimms or defective formatter board.

What to do:

Turn the printer off at the machine, then the mains and leave for 30 seconds. If the error code still shows, try reseating the dimms and formatter board. If this doesn’t solve the problem then replace the dimms and then the formatter board.

HP Error Code:

66 – External Paper Handling Device Error

Explanation:

This fault means there’s a problem with one or more additional paper or envelope trays or finishing units, such as a staple finisher.

What to do:

Turn the printer off, checking the connections between all the accessories and that they move freely, where applicable. If this doesn’t resolve the problem you may have sensor or board problems that require that attention of an engineer.

HP Error Code:

67 – Service Printer Error or Memory Error

Explanation:

Depending up your model this can be a number of different things including: a temporary error, defective paper guide, a break in communication, controller board error or defective SIMMs.

What to do:

Turn off your printer and check that the paper trays are inserted correctly and aren’t damage. Check whether the I/O printer cable is installed correctly and not damaged, perhaps try using a different cable to test. Reseat any SIMMs or replace if necessary. If a controller board needs replacing you may need an engineer.

HP Error Code:

68 – Error in NVRAM. Service Error NVRAM full

Explanation:

The NVRAM is full, meaning some actions can’t be processed.

What to do:

Try resetting the NVRAM. First of all print out a configuration page, you’ll need this to re-enter any details. Now reset by holding down “Reset” or “Cancel Job” for 20 seconds while powered on. Print off a second configuration page and re-enter any details that are missing. If this doesn’t resolve the problem you may need a new formatter board.

HP Error Code:

69 – Duplexer Error has Occurred

Explanation:

The printer has a problem with duplex unit, this is the unit that enables the printer to print double-sided.

What to do:

Check the duplex unit and reseat and clear any obstructions that may be causing the error. If the error persists you may need a new duplex unit.

HP Error Code:

70 – Faulty MIO Card or SIMMs or Wrong Cartridge

Explanation:

Either the SIMM or cartridge installed is incompatible with the printer or the MIO card is faulty (older models).

What to do:

Check the SIMMs or cartridge to ensure they are intended for your machine. Faulty MIO problems are very rare.

HP Error Code:

71 – Faulty MIO Card or SIMMs or Wrong Cartridge

Explanation:

Either the SIMM or cartridge installed is incompatible with the printer or the MIO card is faulty (older models).

What to do:

Check the SIMMs or cartridge to ensure they are intended for your machine. Faulty MIO problems are very rare.

HP Error Code:

72 – Defective Font Cartridge or Formatter Board

Explanation:

Either the font cartridge is defective, or was removed during access, or the formatter board is defective.

What to do:

Turn the printer off and on and see if this resolves the problem. Check the font cartridge is installed correctly. Replace the font cartridge, if unresolved the formatter board may need replacing.

HP Error Code:

79 – Critical Hardware Error has Occurred

Explanation:

Your printer has a defective accessories of some kind, possibly related to memory, I/O cards or a firmware issue.

What to do:

Update to the latest firmware to rule out this issue. If unresolved, remove all cards/accessories and replace one by one to identify what is at fault.

HP Error Code:

80 – Defective Network Card or Formatter Board

Explanation:

Your printer has a defective accessory of some kind, possibly related to memory, I/O cards or a firmware issue.

What to do:

Updated to the latest firmware to rule out this issue. If unresolved, remove all cards/accessories and replace one my one to identify what is at fault. If unresolved the formatter board may need replacing.

HP Error Code:

81 – Defective Network Card or Formatter Board

Explanation:

Your printer has a defective accessory of some kind, possibly related to memory, I/O cards or a firmware issue.

What to do:

Updated to the latest firmware to rule out this issue. If unresolved, remove all cards/accessories and replace one my one to identify what is at fault. If unresolved the formatter board may need replacing.

HP Error Code:

89 – PostScript ROM Failure

Explanation:

Your PS ROM may be improperly located or have damaged pins, or may be defective.

What to do:

Firstly turn the printer off and on to see if this resolves the problem. If not then check the PS ROM for any damage and reseat. If the problem remains then you may need to replace the PS ROM.

HP Error Code:

99 – Firmware Upgrade

Explanation:

There has been a flash firmware failure.

What to do:

You need to either update to the latest flash firmware or replace the flash firmware DIMM.

There are still other HP printer error codes that may come out depending on the printer model you own. You can check on the manual that comes with your HP printers when these codes appear on the printer’s display.

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Notes for class 11 chemistry

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Notes for class 11 chemistry

S.No. Ncert solutions for class 11 chemistry
1  Notes for Class 11 Chemistry  Chapter 1 Some Basic Concepts of Chemistry  
2 Notes for Class 11 Chemistry  Chapter 2 Structure of Atom 
3 Notes for Class 11 Chemistry  Chapter 3 Classification of Elements and Periodicity
4 Notes for Class 11 Chemistry  Chapter 4 Chemical Bonding and Molecular Structure 4
5 Chemistry class 11 notes Chapter 5 States of Matter 
6 Notes for Class 11 Chemistry  Chapter 6 Thermodynamics 
7 Notes for Class 11 Chemistry  Chapter 7 Equilibrium 
8 Notes for Class 11 Chemistry  Chapter 8 Redox Reactions 
9 Notes for Chemistry Class 11 Chapter 9 Hydrogen
10 Important Notes of Chemistry Class 11 chapter 10 The s-Block Elements
11 Important Notes of Chemistry Class 11 chapter 11 The p-Block Elements 
12 notes on organic chemistry class 11 chapter 12 Organic Chemistry – Some Basic Principles and Techniques 
13 notes on organic chemistry class 11 chapter 13 Hydrocarbons 
14 chemistry class 11 notes chapter 14  Environmental Chemistry 

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notes for class 11 chemistry chapter 5


Intermolecular forces

Intermolecular forces are the forces of attraction and repulsion between interacting particles (atoms and molecules). Attractive intermolecular forces are known as van der Waals forces

Dispersion Forces or London Forces

In atoms and nonpolar molecules electronic charge cloud is symmetrical but when the charge cloud becomes more on one side than the other. Dipole develops for few moments. The attraction force between developed dipole is known as dispersion force or London forces. These forces are always attractive.
Interaction energy,                                         E 1/ r6
r is the distance between two interacting particles.
These forces are important only at short distances (~500 pm)

Dipole – Dipole Forces

Dipole-dipole forces act between the molecules possessing permanent dipole. Ends of the dipoles possess “partial charges”. This interaction is stronger than the London forces but is weaker than ion-ion interaction because only partial charges are involved..
Interaction energy for stationary polar molecules,    E 1/ r3
Interaction energy for rotating  polar molecules,    E 1/ r6
Where r is the distance between two interacting particles.
polar molecules can interact by London forces also so cumulative effect of forces in polar molecules increase.

Dipole–Induced Dipole Forces

Permanent dipole of the polar molecule induces dipole on the electrically neutral molecule by deforming its electronic cloud. Attractive forces operate between the polar molecules having permanent dipole and induced dipole.
Interaction energy, E 1/r 6
Where r is the distance between two molecules.
In this case also cumulative effect of dispersion forces and dipole-induced dipole interactions exists.

Hydrogen bond

Strong type of dipole-dipole interaction is hydrogen bonding. This is found in the molecules in which highly polar N–H, O–H or H–F bonds are present. Energy of hydrogen bond varies between 10 to 100 kJ mol–1. hydrogen bonds are powerful force in determining the structure and properties of many compounds,
Hydrogen bond

Properties of gases

Gases are highly compressible.
Gases exert pressure equally in all directions.
Gases have much lower density than the solids and liquids.
The volume and the shape of gases are not fixed. These assume volume and shape of the container.
Gases mix evenly and completely in all proportions without any mechanical aid.

Boyle’s Law (Pressure – Volume Relationship)

According to Boy’s law, at constant temperature, the pressure of a fixed amount of gas varies inversely with its volume.
 Mathematically,                                              P 1/ V
At constant T and n
P = k(1/ V)                                           … (1)
k is proportionality constant
PV= k
If a fixed amount of gas at constant temperature T occupying volume V1 at pressure p1 undergoes expansion, so that volume becomes V2and pressure becomes p2,
p1V1= p2V2= constant
Curve at different constant temperature is known as an isotherm
Density ‘d’ is related to the mass ‘m’ and the volume ‘V’ by the relation
d =  m / V
V = m/d
Plug in equation (1), we get
P = k(d/m)
So that at a constant temperature, pressure is directly proportional to the density of a fixed mass of the gas

cbse question paper for class 12 2014 physics


 cbse question paper for class 12, 2014 physics

General Instructions:
(i) All questions are compulsory.
(ii) There are 30 questions in total. Question Nos. 1 to 8 are very short answer type questions and carry one mark each.
(iii) Questions Nos. 9 to 18 carry two marks each. Questions Nos. 19 to 27 carry three marks each and questions Nos. 28 to 30 carry five marks each.
(iv) There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks each. You have to attempt only one of the choices in such questions.
(v) Use of calculators is not permitted. However, you may use log tables if necessary.
Section A
Question:  1 Define the term ‘Mobility’ of charge carriers in a conductor. Write its S.I. unit 
Question:  2 The carrier wave is given by

C(t) = 2sin(8πt) volt.

The modulating signal is a square wave as shown. Find modulation index.

Question:  3 “For any charge configuration, equipotential surface through a point is normal to the electric field.” Justify. 
Question:  4 Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why? 
Question:  5 Show variation of resistivity of copper as a function of temperature in a graph. 
Question:  6 A convex lens is placed in contact with a plane mirror. A point object at a distance of 20 cm on the axis of this combination has its image coinciding with itself. What is the focal length of the lens? 
Question:  7 Write the expression, in a vector form, for the Lorentz magnetic force F  due to a charge moving with velocity V  in a magnetic field B . What is the direction of the magnetic force? 
Question:  8 The figure given below shows the block diagram of a generalized communication system. Identify the element labelled ‘X’ and write its function.
Section B
  Question:  9
Out of the two magnetic materials, ‘A’ has relative permeability slightly greater than unity while ‘B’ has less than unity. Identify the nature of the materials ‘A’ and ‘B’. Will their susceptibilities be positive or negative? 
  Question:  10
Given a uniform electric field E =5 ×103 i N/C, find the flux of this field through a square of 10 cm on a side whose plane is parallel to the y-z plane. What would be the flux through the same square if the plane makes a 30° angle with the x-axis ? 
  Question:  11
For a single slit of width “a”, the first minimum of the interference pattern of a monochromatic light of wavelength λ occurs at an angle of λa. At the same angle of λa, we get a maximum for two narrow slits separated by a distance “a”. Explain. 
  Question:  12
Write the truth table for the combination of the gates shown. Name the gates used.

                                                           OR

Identify the logic gates marked ‘P’ and ‘Q’ in the given circuit. Write the truth table for the combination.

  Question:  13
State Kirchhoff’s rules. Explain briefly how these rules are justified. 
  Question:  14
A capacitor ‘C’, a variable resistor ‘R’ and a bulb ‘B’ are connected in series to the ac mains in circuit as shown. The bulb glows with some brightness. How will the glow of the bulb change if (i) a dielectric slab is introduced between the plates of the capacitor, keeping resistance R to be the same; (ii) the resistance R is increased keeping the same capacitance?
  Question:  15
State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies. 
  Question:  16
An electric dipole of length 4 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of 43√ Nm. Calculate the potential energy of the dipole, if it has charge ±8 nC. 
  Question:  17
A proton and a deuteron are accelerated through the same accelerating potential. Which one of the two has
(a) greater value of de-Broglie wavelength associated with it, and
(b) less momentum?

Give reasons to justify your answer. 

  Question:  18
(i) Monochromatic light of frequency 6.0 × 1014 Hz is produced by a laser. The power emitted is 2.0 × 10−3 W. Estimate the number of photons emitted per second on an average by the source.
(ii) Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface. 
Section C
  Question:  19
A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. Upto which energy level the hydrogen atoms would be excited?
Calculate the wavelengths of the first member of Lyman and first member of Balmer series. 
  Question:  20
When Sunita, a class XII student, came to know that her parents are planning to rent out the top floor of their house to a mobile company she protested. She tried hard to convince her parents that this move would be a health hazard.
Ultimately her parents agreed :
(1) In what way can the setting up of transmission tower by a mobile company in a residential colony prove to be injurious to health?
(2) By objecting to this move of her parents, what value did Sunita display?
(3) Estimate the range of e.m. waves which can be transmitted by an antenna of height 20 m. (Given radius of the earth = 6400 km) 
  Question:  21
A potentiometer wire of length 1 m has a resistance of 10 Ω. It is connected to a 6 V battery in series with a resistance of 5 Ω. Determine the emf of the primary cell which gives a balance point at 40 cm. 
  Question:  22
(a) Draw a labelled ray diagram showing the formation of a final image by a compound microscope at least distance of distinct vision.

(b) The total magnification produced by a compound microscope is 20. The magnification produced by the eye piece is 5. The microscope is focussed on a certain object. The distance between the objective and eyepiece is observed to be 14 cm. If least distance of distinct vision is 20 cm, calculate the focal length of the objective and the eye piece. 

  Question:  23
(a) A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform.
(b) Suppose the lower half of the concave mirror’s reflecting surface is covered with an opaque material. What effect this will have on the image of the object? Explain.
  Question:  24
(a) Obtain the expression for the energy stored per unit volume in a charged parallel plate capacitor.
(b) The electric field inside a parallel plate capacitor is E. Find the amount of work done in moving a charge q over a closed loop a b c d a.
OR
(a) Derive the expression for the capacitance of a parallel plate capacitor having plate area A and plate separation d.
(b) Two charged spherical conductors of radii R1 and R2 when connected by a conducting wire acquire charges q1 and q2 respectively. Find the ratio of their surface charge densities in terms of their radii.
  Question:  25
(a) State Ampere’s circuital law, expressing it in the integral form.
(b) Two long coaxial insulated solenoids, S1 and S2 of equal lengths are wound one over the other as shown in the figure. A steady current “I” flow thought the inner solenoid S1 to the other end B, which is connected to the outer solenoid S2 through which the same current “I” flows in the opposite direction so as to come out at end A. If n1 and n2 are the number of turns per unit length, find the magnitude and direction of the net magnetic field at a point (i) inside on the axis and (ii) outside the combined system.
  Question:  26
Answer the following:
(a) Name the em waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.
(b) If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.
(c) An em wave exerts pressure on the surface on which it is incident. Justify. 
  Question:  27
(a) Deduce the expression, N = N0e−λt, for the law of radioactive decay.
(b) (i) Write symbolically the process expressing the β+ decay of Na1122. Also write the basic nuclear process underlying this decay.
(ii) Is the nucleus formed in the decay of the nucleus Na1122, an isotope or isobar?
Section D
  Question:  28
(a) (i) ‘Two independent monochromatic sources of light cannot produce a sustained interference pattern’. Give reason.
(ii) Light waves each of amplitude “a” and frequency “ω”, emanating from two coherent light sources superpose at a point. If the displacements due to these waves is given by y1 = a cos ωt and y2= a cos(ωt + ϕ) where ϕ is the phase difference between the two, obtain the expression for the resultant intensity at the point.

(b) In Young’s double slit experiment, using monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ, is K units. Find out the intensity of light at a point where path difference is λ/3.


OR

(a) How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a Polaroid gets polarised?

(b) A beam of unpolarised light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarised, when μ = tan iB, where μ is the refractive index of glass with respect to air and iB is the Brewster’s angle. 

  Question:  29
(a) Describe a simple experiment (or activity) to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it.
(b) The current flowing through an inductor of self inductance L is continuously increasing. Plot a graph showing the variation of
(i) Magnetic flux versus the current
(ii) Induced emf versus dI/dt
(iii) Magnetic potential energy stored versus the current.
OR​
(a) Draw a schematic sketch of an ac generator describing its basic elements. State briefly its working principle. Show a plot of variation of
(i) Magnetic flux and
(ii) Alternating emf versus time generated by a loop of wire rotating in a magnetic field.
(b) Why is choke coil needed in the use of fluorescent tubes with ac mains?
  Question:  30
(a) State briefly the processes involved in the formation of p-n junction explaining clearly how the depletion region is formed.

(b) Using the necessary circuit diagrams, show how the V-I characteristics of a p-n junction are obtained in

(i) Forward biasing
(ii) Reverse biasing

How are these characteristics made use of in rectification?
 

OR

(a) Differentiate between three segments of a transistor on the basis of their size and level of doping.

(b) How is a transistor biased to be in active state?

(c) With the help of necessary circuit diagram, describe briefly how n-p-n transistor in CE configuration amplifies a small sinusoidal input voltage. Write the expression for the ac current gain.