1. What is lens?
Device made up of glass which forms the image of object by the refraction of light.
2. How can you distinguish convex and concave lens?
By touching as middle part of convex is thick where as that of concave is thin.
3. Why convex lens is called conversing lens?
Because the refracted rays from lens intersect at a point.
4. Why concave lens is called diverging lens?
Because the refracted rays from the lens diverged.
5. Define focal length and focus?
The point in which the refracted rays from the lens intersect is called Focus. The distance between centre of lens and focus is called focal length.
6. What is real image?
Image which can be obtained on screen 7. Define magnification.
The ratio of size of image to the size of the object.
8. Define power of lens.
The ability of conversing or diverging of rays.
9. Write down the formula of power and its unit.
P=1/f and its unit is dioptre
10. What is the nature and position of image formed by convex lens when object is placed at different points?
Position of objects Position of image Size and nature of image
∞ F Real, inverted & highly
diminished Beyond 2F In between F and 2F Real, inverted &
diminished
Between F and 2F Beyond 2F Real, inverted & magnified
2F 2F Real , inverted and equal in
size
F ∞ Real, inverted and highly
magnified.
Between F and O Same side Virtual, erect and large.
11. What is short sightedness? How it can be removed?
If a person can see the nearby object Cleary but cannot see distant object Cleary is called short sightedness. This defect can be removed by using spectacles containing concave lens.
12. What is long sightedness? How it can be removed?
If a person cannot see the nearby object Cleary but can see the distant object Cleary is called Long sightedness. This defect can be removed by using spectacles containing convex lens.
13. What is near and far point for a healthy eye?
Near point 25 cm Far point infinity 14. What is microscope?
Device which is used to observe smaller object in magnified form.
15. What is telescope?
Telescope is an optical device which is used to observe the distant objects clearly.
16. Which lens is bigger in microscope?
Eye lens
17. Which lens is bigger in Telescope
Physics 30
Objective lens.
18. What is the nature and position of image formed by concave lens when object is placed at different points?
Position of objects Position of image Size and nature of image
Infinity F Virtual ,erect and
highly diminished Between F and Infinity Between F and O Virtual, erect and small.
Experiment No. 21
To study the Series & Parallel combination of Cells.
Materials Required:
Three cells (1.5V)
Voltmeter
Connecting wire Theory:
A single cell may not provide sufficient current or P.d on electrical circuit so cells are connected in series & parallel combination according to the needs of electrical circuit. If the +ve terminal of the one cell is connected to the ve terminal of the second and so on it is called series combination. If the cell with e.m.f. V1, V2, V3 are connected in series then the equivalent voltage is,
V = V1+V2+V3
If the +ve terminal of all the cells are connected together at one common point and
ve terminals at another common point, it is called parallel combination. If the cells with
e.m.f. V1, V2, V3 is connected in parallel then the equivalent voltage is, V=V1=V2=V3
Procedure:
Take three different cells having e.m.f. 1.5V.
Take a voltmeter and measure e.m.f. of each cell separately.
Connect three cells in series as shown in the fig.Ist and measure equivalent voltage Fig.: Series & parallel combination of cells
across the resistance R by using voltmeter and fill the table 1 below:
Again connect next three cells in parallel as shown in the 2nd fig.
Measure the equivalent voltage across the resistance R by using voltmeter and fill the table (2) below.
Observation Table:
Table No.1 (series combination of cells)
V1 V2 V3 V Remarks
V = V3+V2+V1
Table No.2 (Parallel combination of cells)
V1 V2 V3 V Remarks
V = V3+V2+V1
Conclusion:
From the above experiment it is found that the equivalent voltage of number of cells is equal to the sum of individual voltage of each cell in series combination where as it is equal to the individual voltage in parallel combination.
Precaution:
The batteries must be well.
The polarities must be connected correctly.
Experiment No.22
Project work
To prepare a Model of Series & Parallel combination of bulbs.
Materials Required:
Bulbs (6)
Switches(4)
Batteries(9V and 9V)
Connecting wires Procedure:
Take three bulbs and 9V batteries.
Connect the circuit as shown in the figure Ist by using two bulbs.
Switch on the circuit and observe the brightness of the bulb.
Add one more bulb in the circuit and observe the change in brightness and fill the table below.
Connect two bulbs in parallel with 9V batteries as shown in the 2nd figure and observe the brightness.
Physics 32
Add one more bulb in the circuit and observe change in brightness of the bulb and fill the table below.
Fix all the bulbs and wires in the chart board paper.
Submit it to your science teacher.
Observation Table:
(Give tick for suitable one) For series combination
Fig. No. Voltage No. Of Bulbs Brightness of the bulb More Less 1
2
For parallel combination
Fig. No. Voltage No. Of Bulbs Brightness of the bulb More Less 1
2 Precaution:
Circuit must be connected carefully.
Suitable length of the wire must be used.
Experiment No.23
To study the Magnetic effect of current by using Compass Needle.
Materials Required:
Compass Needle
Connecting wires
Cells Theory:
Compass needle is a device which
Fig.: Series and Parallel Combination of bulbs
contains magnetic compass at its tips placed horizontally. When a wire is placed parallel to the magnetic compass and current is passed through it, the deflection of magnetic compass is observed. This is because the wire shows the property of magnet when current is passed through it. This is called as magnetic effect of current.
Procedure:
Take a compass needle with a magnetic compass at its tip.
Stretch the wire parallel and above the magnetic compass with the help of stand.
Pass electric current to the wire by connecting batteries.
Observe the deflection of the Magnetic compass.
Remove the connection of the batteries.
Observe the position of the magnetic compass i.e. magnetic compass comes in its original position.
Interpretation:
When current is passed through the wire it becomes magnet so deflection is observed but when batteries are removed magnetic property is also lost.
Conclusion:
From the above experiment it is found that when current is passed through a conductor it becomes a magnet until current is passed through it, so the magnetic compass shows deflection.
Precaution:
The wire must be placed parallel to the magnetic compass.
Experiment No.24
To study the Magnetic Field of any conductor when electricity is passed through it.
Materials Required:
Paper
Wire
Iron dust
cells
switch Theory:
When current is passed through any conductor it behaves as a magnet. This is called magnetic effect of current. So when Current is passed through any conductor,
the region around the conductor up to Iron dust
cells
Card board Paper Conductor
Physics 34
which the magnetic force can be experienced is called magnetic Field.
Procedure:
Take a thick paper sheet.
Make small hole on the centre of paper and insert wire through it.
Connect both the terminals of wire with the batteries & with switch as shown is figure.
Spread iron dust on the whole surface of paper.
Switch on the circuit and observed the experiment.
Observed the area up to which the iron dusts are attracted by the wire.
Interpretation:
When current is passed through the wire it becomes magnet so iron dust are attracted.
Conclusion:
From the above experiment it is found that when current is passed through any conductor it behaves as magnet and it sets magnetic area around it.
Precaution:
Take large sheet of paper.
The wire & batteries must be well.
Circuit must be connected carefully.
Experiment No.25
To Prepare Electromagnet in Laboratory.
Materials Required:
Iron rod
Wire
Battery(6V)
Iron pins Theory:
When electricity is passed through any solenoid it behaves like a magnet. This is called electro magnet. This is a temporary magnet as it loses magnetic properties, if there no current in the wire. The solenoid is formed by winding a length of insulated wire around a magnetic material such as iron rod.
Fig.: Electromagnet Fig.: Figure to show magnetic effect of current
Procedure:
Take an iron rod and insulated cupper wire.
Wind the copper wire around the iron bar of 80-90 turns. So that the solenoid is formed.
Connect the two terminals of wire with battery.
Put iron pins on the rod then observed the attraction of pins toward the rod.
Remove the connection of battery and observe the falling of pins from the rods.
Interpretation:
When current is passed through the wire, iron rod is changed into electromagnet.
Conclusion:
From the above experiment it is found that the iron rod acts as a magnet when a current is passed through it.
Precaution:
The no. of winding must be greater than 80 turns.
The e.m.f. of battery must be greater than 5V.
The wire must be insulated.
Experiment No.26
To study the Electrolysis of Water.
Materials Required:
Two carbon-rods.
Two test tubes.
Cells.
Hydrochloric Acid (HCl)
Water
Beaker
Wires
Voltmeter Theory:
Electrolysis is the process of decomposition of compounds either in molten state or in aqueous solution by the passes of electric current through it. For electrolysis of water when dilute Hydrochloric Acid (HCl) is added into water they dissociated into ions and become good conductor of current.
Chemical Reaction:
H2O H+ + OH
Physics 36
HCl H+ + Cl At Anode:
4OH → OH + e 4OH → 2H2O + O2 Again, Cl + H+→HCl At Cathode:
H+ + e- →H 4H →2H2
Procedure:
Take a voltmeter and place two carbon electrodes in it.
Pour sufficient amount of water in voltmeter.
Fill two test tubes completely with water and invert them over electrodes.
Add few drops of dilute Hydrochloric Acid (dil.HCl) to the water.
Connect electrodes to the battery as shown in the figure; the voltage must be greater than 3V.
The liquid begins to conduct so that the bubbles are seen around electrodes.
Observe the gas collected in the test tubes.
Interpretation:
When a burning match stick is taken to the mouth of test tubes, in one test tube stick glows brightly this is Oxygen gas whereas it extinguishes with pop sound in next, it is Hydrogen gas.
Result:
From the above experiment it is found that when electric current is passed through water electrolysis takes place and hydrogen and oxygen gas are formed.
Precaution:
Little amount of Hydrochloric Acid (HCl) should be added drop wise.
The voltage of battery must be greater than 3V.
Two electrodes must be placed sufficiently apart.
Experiment no.27
To study the Electroplating of Copper on Iron.
Materials Required:
Voltammeter (beaker)
Copper plate
Iron nail
copper sulphate (CuSO4)
Connecting wires
Fig.: Electrolysis of water
Battery Theory:
Electro plating is the process of putting metallic coating on a metal or other conducting surface by electrolysis process.
In this experiment copper is plated on iron nail. The chemical
Reactions are:
CuSO4 Cu++ + SO4 At Anode:
Cu → Cu++ + 2e At Cathode:
Cu++ + 2e → Cu Procedure:
Take a voltammeter with copper sulphate (CuSO4)solution.
Put clean iron nail in copper plate in a voltammeter and connect it to the battery as shown in fig.
Allow the electric current to pass through it.
Observe copper on iron nail after some time.
Stop the process when the plating is complete.
Result:
From the above experiment it is found that when electricity is passed through a solution of salt of copper with Cu plate as anode, iron nail as cathodes and copper rod as electrodes, plating of copper on iron is observed.
Precaution:
+Ve terminal of battery must be connected to the copper plate and -ve terminal to the iron nail.
The battery must be greater than 6V.
The solution of copper sulphate must be concentrated.
Experiment No.28
To study the Electromagnetic Induction in Laboratory.
Materials Required:
U-shaped Magnet
Conductor (wire, different from connecting wire)
Fig.: Electroplating of copper on iron
Physics 38
Connecting wire
Galvanometer Theory:
If any conductor placed in magnetic field is allowed to move magnetic flux linked with the coil changes and e.m.f is produced this is called electromagnetic induction.
And the produced e.m.f. is called is called induced e.m.f.Generator and dynamo are based on this principle.
Procedure:
Take a U-shaped magnet.
Place a conductor (wire different from cupper wire) in between the two arms of the magnet.
Connect two ends of the wire to a galvanometer.
Move the conductor within the region of the two arms.
Observe the deflection of the galvanometer when the conductor is brought to rest also.
Conclusion:
From the above experiment it is found that e.m.f. is induced whenever conductor is moved within magnetic field.
Precaution:
Strength of the Magnet must be high.
Conductor must be moved gently.
Experiment No.29
Project Work
To Prepare a Model of Electric Bell in Laboratory.
Materials Required:
U-shaped iron rod
Screw nail
Iron plate
Fig.: Electromagnetic induction
Connecting wires
switch
Hammer
Gong Theory:
Electric bell is an electronic device which can convert electrical energy into kinetic energy and then into sound energy. It is based on the principle of electromagnet.
Procedure:
Take U-shaped iron rod.
Wind insulated wire around it.
Connect one terminal of wire to the battery along with switch.
Connect next terminal to the iron plate fitted with screw nail and other part as shown in the figure.
Switch on the circuit and observe the beating of hammer on gong.
Fix this device on a card board paper and submit it to your science teacher.
Result:
From the above experiment Electric Bell is prepared in Laboratory.
Precaution:
The number of winding must be as much as possible.
The U-shaped iron rod must be soft.
Connect the circuit carefully.
Viva Questions
Electricity and Magnetism 1. What is cell?
The source of electricity which convert chemical energy into electrical energy.
Fig.: Electric bell
Physics 40
2. Define circuit.
The closed path formed by cell, switch, load etc in which current can flow.
3. What is current?
The rate of flow of charge in called current.
4. What is unit and formula of current?
Current (I) = Q/T and its unit is A.
5. What is the unit of charge?
Coulomb.
6. What is series combination?
If the +ve terminal of the one cell is connected to the ve terminal of the second and so on it is called series combination.
7. What is parallel combination?
If the +ve terminal of all the cells are connected together at one common point and ve terminals at another common point, it is called parallel combination.
8. Which combination is used in house wiring?
Parallel.
9. Write full form of AC and DC.
AC=Alternate current DC=Direct current
10. What is the frequency of electricity supplied in Nepal?
50 Hz
11. What is the voltage of electricity supplied in Nepal?
220 volt
12. What is the meaning of 50 Hz AC?
The polarity of current changes 50 times per second.
13. What is the color of different wire used in house wiring?
Phase wire= red or brown Neutral wire= black or blue
Earthing wire= green or yellow lines in green.
14. What is fuse made up of?
Alloy of tin and lead
15. What capacity of fuse must be used in a circuit in which current of 4A flows?
5A
16. On which wire switch is connected?
Phase wire
17. On which wire fuse is connected?
Phase or live wire 18. Define 1 unit.
When device of electric power 1 kW is operated for an hour then the consumed electricity is called 1 unit.
19. What is the equivalent voltage when e.m.f V1, V2 and V3 are connected in series and parallel?
Series, V=V1+V2+V3
Parallel, V= V1 = V2 = V3
20. What is the equivalent resistance when resistors R1, R2, R3 are connected in series and parallel?
Series R=R1+R2+R3
Parallel, I/R=1/R1+1/R2+1/R3
21. What is the chemical effect of current?
Chemical reaction due to the passage of current is called chemical effect of current
22. What is electrolysis?
Electrolysis is the process of decomposition of compounds either in molten state or in aqueous solution by the passes of electric current through it.
23. Which gas is formed in large amount during electrolysis of water?
Hydrogen gas
24. Which gas is formed at anode and at cathode during the electrolysis of water?
Anode-Oxygen Cathode-Hydrogen
25. What are the uses of electrolysis of water?
Dissociation of H2O into H2 and O2 26. Define electroplating.
Electro plating is the process of putting metallic coating on a metal or other conducting surface by electrolysis process.
27. What must be the anode during the electroplating of copper on iron?
Copper
28. Write one use of electroplating.
Coating of valuable metal on normal metal
Physics 42
29. What will happen if the polarity of battery is reversed during the electroplating of cu on Zn?
Plating of Zinc on Copper occurs.
30. What is electromagnet?
When electricity is passed through any solenoid it behaves like a magnet. This is called electro magnet.
31. Why electromagnet is called temporary magnet?
This is a temporary magnet as it loses magnetic properties, if there no current in the wire.
32. What are the ways to increase strength of electro magnet?
By increasing no. of turns
By increasing voltage across the wire 33. What is electromagnetic induction?
If any conductor placed in magnetic field is allowed to move magnetic flux linked with the coil changes and the e.m.f is produced this is called electromagnetic induction.
34. What is Fleming's Right hand rule?
When thumb, forefinger and middle finger of right hand are held perpendicular and the motion of conductor is set along the direction of thumb, the direction of magnetic field along forefinger then middle finger gives the direction of induced current.
35. Which device is based on electromagnetic induction?
Generator and dynamo
36. What is the meaning of 50 W written in bulb?
Bulb can convert 50 joule electrical energy into heat and light energy in 1 sec.
37. What is advantage of series combination of bulbs?
Brightness of the bulb can be changed.
38. What is the advantage of parallel combination of bulbs?
Bulb can withstand long time.
Chemistry
Experiment No.30
To study the relation between Rate of Reaction and Concentration of Reactants.
Material Required:
White sheet of paper
Conical flask
Sodium Thiosulphate (Na2S2O3)
Hydrochloric Acid (HCl)
Water
Stopwatch Theory:
The rate of chemical reaction is defined as change in concentration of any one of the reactants or products per unit time to complete the reaction. The rate of reaction depends upon the concentration, Temperature, Catalyst and the nature of the reactants. In general the Rate of Reaction increases with increase in Temperature and vice-versa. And the rate of reaction Increases with increase in concentration of the reactants.
Procedure:
Make a solution of 4 gm Sodium Thiosulphate in 100 ml water in the first beaker.
Make solution 20 ml conc. HCl and 100 ml water in next beaker.
Make a solution of 30 ml Sodium Thiosulphate and 20 ml water in a conical flask.
Mark black "X" in a white chart paper and place conical flask above it.
Fig.: Variation of Rate of Reaction with Concentration