SCIENCE QUESTION PAPER - 6
Answer the following Q. No. 1 to 18 (within the limit of 10 to 20 words) as directed :
(1 mark each)
Fill in the blanks so as to make each of the following statements true :
1. Largest part of brain is ..thalamus........
2. In human beings, sex is determined by..genes.
3.An element 'B' belongs to the seoond period and group 13, formula of its oxides.B2O3.....
4.A very short period contains ...2..... elements.
State whether the following statement are true or false.
5. Rusting is a double decomposition rreaction.False
6.A voltmeter has a low resistance.False
7. Neurohypophysis is associated with Growth Hormone (GH)False
Choose the correct option and write it with answer from those given below multiple
choice questions : (MCQs)
8. It is important to make small check dams across the flooded gullies because they
(i) Hold water for irrigation
(ii) Hold water and prevent soil erosion
(iii) Recharge groundwater
(iv) Hold water permanently
(a) (i) and (iv)
(b) (ii) and (iii)
(c)(iii) and (iv)
(d) (ii) and (iv)
9. Flow of energy in an ecosystem is always
(a) unidirectional (b) bidirectional
(c) multidirectional (d) no specific direction
10. Choose the correct statement
(a) Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside the earth
(c) Hydro and wind energy plants are non-polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off
11. Exchange of genetic material takes place in
(a) Vegetative reproduction (b) Asexual reproduction
(c) Sexual reproduction (d) Budding
Answer the following questions as directed :
12. Which type of lens should be used to correct the presbyopia?
Bi-focal length
13. What is the power of a convex lense whose focal length is 50 cm?
(+)2.0 D
14. Structural formula of benzene is:
15. Structural isomers of C4H10
16. Which virus cause AIDS?
HIV OR Immunodeficiency virus
Section : B
"Answer the following questions no. 17 to 26 (within the limit of 40 to 50 words) as
directed : (2 marks each)
17. The pH a salt used to make tasty and crispy pakoras,is 14. Identify the salt and write a chemical equation for its formation, List its two uses.
Answer :-The pH of salt used to make tasty and crispy pakoras is 9.
The baking soda is most commonly used in making tasty pakoras because it's basic in nature. It's chemically known by the name sodium bicarbonate.
The reaction that take place during cooking of food and adding baking soda in it is as follows:
2NaHCO3 => Na2CO3 +H2O +CO2
1. Sodium bicarbonate is a very effective product to eliminate the annoying black spots that often appear in the T area of the face
2.Gargling baking soda prevents flu and throat infections.
18. What would you observe when zinc is added to a solution of iron (ll) sulphate? Write the chemical reaction that takes place.
We observed that the green color solution of iron sulphate changes it color and become colorless .The silver color zinc changes into black.
The equation take place as follows--
Fe2SO4+Zn => Znso4+2Fe
19. Nitrogen (atomic number 7) and phosphorous (atomic number 15) belong to group 15 of
the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Answer :- electronic configuration
Nitrogen- 2.5
Phosphorus- 2.8.5
Nitrogen and phosphorus belongs to group 15. the place of phosphorus is below nitrogen in the group. As we know that the electronegativity of the elements decreases a on going from top to bottom in a group, that's why nitrogen is more electronegative.
OR
19. Why do you think noble gases are placed in a separate group?
Answer :- Nobel gases are chemically inert and are present in extremely low concentration in atmosphere. Thus owing to their similar inert behaviour and similar electronic configuration, they are placed in a separate group.
20. Write the events that occur during photosynthesis.
Anser :-List the three events that occur duringthe process of photosynthesis. ... The three events that occur during the process of photosynthesis are: (i) Absorption of light energy bychlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen
OR
20. Explain the process of digestion in stomach.
Answer :- Strong stomach muscles contract and relax thereby churning the food.
Gastric glands secrete dilute hydrochloric acid and pepsinogen directly into the stomach.
Dilute HCl kills many germs and converts pepsinogen into a more useful enzyme pepsin, which acts on proteins in presence of HCl converting them into peptones.
The semi-digested food slowly enters the small intestine in the form of a thick paste called chyme.
21.State the changes observed in a flower after fertilization,
Answer :- After fertilization, the following changes are observed in a flower: There is formation of a diploid zygote and it develops into an embryo, which forms the future plant. The endosperm cells serve as a source of nutrition for the developing embryo. The ovule becomes the seed.
22.List four properties of the image formed by a convex mirror.
characteristics of image formed by convex mirror are
1) it's a virtual image
2) it located behind the convex mirror
3) it reduce in size ( I.e smaller than the object)
4) it's an upright image
23. Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minute?
Answers
For T.V set
Power (P) = 250w,
Time (t) = 1hr=60×60=3600s
for toster
power=1200W
time =10min = 10*60 =600s
E=P*T
Energy consumed by the TVset = 250*3600 =9*105J
∴ Energy consumed by a toaster = 1200 × 600 = 7.2× 105J
∴ the energy consumed by a 250 W TV set in 1 h is more than the energyconsumed by a toaster of power 1200 W in 10 minutes
OR
23. How many 176 resistors ( in parallel) are required to carry 5A on a 220 V line?
Ans: For x number of resistors of resistance 176 Ω,
Here Supply voltage, V = 220 V
Current, I = 5 A
Equivalent resistance of the combination = R, given as
1/R = X × (1/176)
R = 176/x
From Ohm’s law,
V/I = 176/x
X=176×I/V = 176 ×5/220 = 4
∴four resistors of 176 Ω are required to draw the given amount of current.
24. An electric oven of 2 kW power rating is operated in a domestic electric ciruit (220V) that has a current rating of 5 A. What result do you expect? Explain.
Power = V×I
2kW = 220 × I
I = 2000/220
I = 9.09 A
As the amount of current flowing in the conductor is more than 5 A, the fuse will get broken and hence the circuit will get open.
25. Give difference between producers and consumers.
Answer:- Producer makes its own food; Consumer obtains energy by feeding on others.
Producers are independent; Consumers are dependent.
Producers use photosynthesis; Consumers use respiration.
Producers concentrate energy into complex molecules; Consumers convert these into simpler molecules.
26. What is meant by global warming?
Global warming is the observed and projected increases in the average temperature of Earth’s atmosphere and oceans.
OR
26. List four advantages of water stored under the ground.
Four advantages of water stored in ground :
1. it is less polluted as it is not exposed to humans and animals for contamination
2. it is fit for drinking as it is a source of fresh water
3. it is used for irrigation with the help of tube wells
4. it can be used throughout the year even in dry seasons when most of the surface water gets evaporated.
Section : C
Answer the following Q. no. 27 to 34 in short (within the limit of 60 to 80 words) as
directed. (3 marks each)
27. Name different types of chemical reactions. Give one example for each.
Types of Chemical Reactions with Examples
1) Combustion/Burning Reactions:
Reaction of some combustible matters with oxidizing elements like oxygen is called combustion reactions.After these reactions oxidized products are produced. In general, these reactions are exothermic.To have combustion reaction we must have; combustible matters, oxidizing element and necessary temperature.Examine following combustion reaction samples;
Ca(s) + 1/2O2(g) → CaO(s) + Heat
2Fe(s) + 3/2O2(g) → Fe2O3(s) + Heat
If compounds including C and H elements burn with necessary O2, products are H2O and CO2.
Example:
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) +Heat
C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(g) + Heat
2) Combination/Synthesis Reactions:
More than one matters combine and form new matter is called combination or synthesis reactions.
X + Y → XY
2H2(g) + O2 → 2H2O(l)
N2(g) + 3H2(g) → 2NH3(g)
3) Decompositions/Analysis Reactions:
These reactions are opposite of combination reactions. One compound breaks down to other compounds or elements in decomposition reactions. For example;
XY → X + Y
2H2O(l) → 2H2(g) + O2(g)
CaCO3(s) → CaO(s) + CO2(g)
4. Displacement/Replacement Reactions:
An element reacts with compound and replace with an element of that compound. For example;
Example:
Mg(s) + Cu(NO3)2(aq) → Mg(NO3)2(aq) + Cu(s)
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
If two elements or compounds replace, we call them double displacement reactions. For instance;
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
Ag replace with Na and NO3 replace with Cl.
28. You are provided with magnesium ribbon and sulphur powder. Explain with the help of
an activity that metal oxides are basic and non-metal oxides are acidic in nature.
Answer :- To test the nature of oxides formed by metals and non-metals. Materials Required: Sulphur powder, Mg ribbon, water, blue litmus paper, red litmus paper.
Procedure: 1.Take magnesium ribbon with a pair of tongs and burn it in flame in the presence of air.
2.Collect the product formed and dissolve it in warm water.
3.Add red litmus paper into it.
4.Observe the change in colour and decide the nature of the oxide formed.
5.Burn sulphur in a deflagrating spoon in the presence of air and dissolve the oxide formed in water.
6.Dip blue litmus paper into the solution and observe the changein the colour and decide the nature of the oxide formed.
Observation: The oxide formed by metal turns red litmus blue whereas oxide of non-metal turns blue litmus red.
Chemical Reaction:
2Mg + O2 => Mg0
MgO + H2O => Mg(OH)2
S + O2 => SO2
SO2 + H2O => H2SO3
Conclusion: Most of the metallic oxides are basic in nature whereas most of the non-metallic oxides are acidic in nature.
OR
28. Show that for rusting of iron, both air and moisture are required.
Take three test-tubes. Place clean iron nails in each test-tube.
• Pour some water in test-tube-1, cork it.
• Pour water (boiled/distilled) in test-tube-2, add some oil and cork it.
• Put some anhydrous calcium chloride in test-tube-3 and cork it.
• After 2-3 days we observe that the nails in test-tube 1 rust because they are exposed to air and water both, while nail in test-tube 2 and 3 do not rust. This shows rusting of iron takes place in the presence of air and moisture both.
29. What is the importance of hypothalamus?
Answer :- HYPOTHALAMUS
The important function of hypothalamus is to link the nervous system to the endocrine system via the pituitary gland.
It also secretes neurohormones. These hypothalamic hormones stimulate or inhibit the secretion of pituitary hormones.
It maintains homeostasis in the body and regulates pH balance , temperature control, blood pressure and respiration.
It is also involved in autonomic function control, endocrine function control and motor function control.
It controls hunger , thirst and the intake of food and water, sleep and wake cycles as well as controls defensive behaviour.
30. Describe the menstrual cycle.
An egg is released from either of the ovaries every 28 days. The unfertilized egg is alive for 24 hours after ovulation. Uterus prepares itself to receive the foetus. As a result, the Endometrium thickens.
If fertilization doesn’t take place, then no zygote is formed. Therefore, endometrium breaks which results in bleeding through vagina.
Process of bleeding though vagina due to breakage of endometrium is termed as ‘Menstruation’. This bleeding lasts for 2-6 days. This occurs approx. 14 days after ovulation.
Since Menstruation occurs every 28 days; this is also referred as Menstrual cycle
Menstrual cycle in a woman continues till 45-55 years of age, post which ovary becomes dormant. No ovulation, no menstruation occurs after this. This is termed as “Menopause”
31. What are the probable reasons for selection of pea plants by Mendel for his experiment?
Answer :- Gregor Johannes Mandel was a great biologist. He selected the pea plant for the following reasons:-
1. Pea plants have a large no. of contrasting characters.
2. The lifespan of pea plant is quite small which makes it suitable for carrying out experiments.
3.It is easier to cross pollinate and self pollinate pea plants.
4. They have good resistance to diseases and have an ideal survival rate.
5. They are easy to emasculate and cultivate.
OR
31. Explain how sexual reproduction gives rise to more viable variation than Asexual
reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Sexual reproduction results from the fusion of gametes produced by male and female. Sexual reproduction causes more viable variations because:
→ There might be an error in the copying of DNA, though the event is rare.
→ Segregation of chromosome of maternal and paternal origin at the time of gamete formation is random.
→ There is an exchange of genetic material between homologous chromosomes during formation of gametes.
In case of asexual reproduction, variation is significantly less since only a single parent is involved. Very small changes occur due to inaccuracies during DNA copying that pass on to the progeny. Thus, offsprings of asexual reproduction are more or less genetically similar to their parents. So, it can be concluded that evolution in sexually reproducing organisms proceeds at a faster pace than in asexually reproducing organisms
32. With the help of a ray diagram show the type of images formed when object is placed at the following positions in front of a concave mirror :
(a) at infinity (b) beyond C (c) at C (d) between C and F (e) at C (f) between F and P
Ray Diagrams for a Concave Mirror
For a concave mirror, there are six possible positions where the object can be positioned and an image is formed:
a. Object is positioned at infinity
b. Object is positioned between infinity and center of curvature(c)
Here the object MN is placed between infinity and center of curvature (c) of a concave mirror, then a ray MP parallel to the principal axis and another ray MQ that pass through the center of curvature(c) intersect each other at M’ after reflection between focus (f) and center of curvature (c). Therefore the properties of the images formed here are that the image formation is between principal focus (f) and center of curvature (c), the image formed is diminished and real and inverted.
c. Object is positioned at Center of Curvature
When the object MN is placed the at the center of curvature (c), then a ray MP parallel to the principal axis and another ray MQ that passes through the principal focus (f) after reflection, intersect each other at point M’ right below where the object MN is positioned. Hence the properties of the images formed in this case are that image is formed at the center of curvature, the image is the same size as the object and images are real and inverted.
d. Object is positioned between the center of curvature (c) and principal focus (f)
Object MN is placed between the center of curvature (c) and principal focus (f), then the ray MP parallel to the principal axis and another ray MQ passing through principal focus (f) intersect each other beyond the center of curvature (c) at point M’. Hence the properties of the images formed here are that the image is formed beyond the center of curvature (c), and the image is real and inverted.
e. Object is positioned at principal focus (f)
Object MN is positioned at the principal focus (f), then ray MP parallel to the principal axis passes through principal focus (f) giving the reflected ray PS. Second ray MQ that passes through the center of curvature is reflected along the same path giving the reflected ray QR. Here, since the rays, PS and QR become parallel to each other and therefore the image formation is at infinity. Here the properties of the images formed are highly enlarged images and real and inverted images.
f. Object is positioned between principal focus (f) and pole (p)
Ray Diagram
Now, since the reflected rays PS and QR are diverging away hence cannot intersect each other, hence reflected rays PS and QR are extended behind the mirror by dotted lines. In doing so, rays PS and QR appear to intersect each other at point M’ backwards. Therefore, the properties of the images formed here are formed behind the mirror, images are highly enlarged, images are virtual and erect.
OR
32.Draw and explain the ray diagram formed by a convex mirror when
a.object is at infinity
b. object as at infinite distance from the mirror
There are only two possibilities of position of object in the case of a convex mirror, i.e. object at infinity and object between infinity and pole of a convex mirror.
Object at infinity: When the object is at the infinity, a point sized image is formed at principal focus behind the convex mirror.
Properties of image: Image is highly diminished, virtual and erect.
Object between infinity and pole: When the object is between infinity and pole of a convex mirror, a diminished, virtual and erect image is formed between pole and focus behind the mirror.
Properties of image: Image is diminished, virtual and erect.
33.To study the resisitance and current relationship in a parallel circuit.
Aim
To determine the equivalent resistance of two resistors when connected in parallel.
Materials Required
A battery, a plug key, connecting wires, an ammeter, a voltmeter, rheostat, a piece of sand paper and two resistors of different value.
Procedure
Keep the key off and make all the connections as shown in the given figure I.
When the circuit is connected appropriately insert the key.
Note three readings of ammeter and voltmeter for the resistors R1 and R2 separately.
Now connect the circuit as shown in figure II below.
The resistors are connected in parallel and voltmeter is also connected in parallel.
Use the rheostat and record three different readings of ammeter and voltmeter.
Remove the key.
Do the calculations from the observation table.
Circuit Diagrams
Observation Table
No. of
Observations
(Ist Resistor)
V A V/A=R Mean resistance
(a) 0.01 0.01 1 R1 = 1 Ohm
(b) 0.02 0.02 1
(c) 0.04 0.04 1
R2
(2nd Resistor)
(a) 0.02 0.01 2 R2 = 2 Ohm
(b) 0.06 0.03 2
(c) 0.08 0.04 2
1/Rp= (1/R1)+ (1/R2)
(a) 0.026 0.04 0.67 Rp =0.6
(ParallelCombination) 1/ Rp =1.5
Result
The calculated value of 1/Rp = (1/R1) + (1/R2) = 1.5 Ω
The experimental value of 1/Rp = 1.5 Ω
The equivalent resistance (Rp) is less than the individual resistance (R1 or R2)
34. Explain the transformation of energy in hydroelectric power plant.
Dams are constructed at heights to obstruct the flow of water and store it. The stored water has Potential Energy.
Water stored in heights now is allowed to flow to low levels. The potential energy is converted to kinetic energy and moves the turbines.
Electricity is produced.
This is called Hydroelectricity because the potential energy of water which is stored at elevated heights is converted into kinetic energy of flowing water which in turn is converted electricity
It is a renewable source of energy, since rainfall comes over and over again.
Most of the electricity in India is generated in this method. Since there are not many natural waterfalls, dams are constructed to store water at heights and then allowed to fall and this energy is used to move turbines and thereby generate electricity
Section : D
Answer the following Q. no. 35 to 39 in detail (within the limit of 90 to 120 words)
directed : (4 marks each)
35. Explain mechanism of breathing.
Now, the air present in air sacs of the lungs is rich in C02. When we breathe out air, the diaphragm relaxes which results in the decrease in volume of chest cavity. This contraction pushes the air from the lungs into the trachea, nostrils and then out of the body into air. Breathing in air is called inhalation and breathing out air is called exhalation.
Mechanism of gaseous exchange during respiration: The oxygen is carried by blood to all the parts of the body. As the blood passes through the tissues of the body, the oxygen from the blood diffuses into the cell, whereas the C02 which is produced during respiration diffuses into the blood and is carried to the lungs.
36. Explain scattering of light.
Scattering of light is the phenomenon in which a
part of the incident light is dispersed in different
directions.
Appearance of blue sky: The molecules of air and
other fine particles in the atmosphere have a size
smaller than the wavelength of visible light. So, they
are more effective in scattering light of shorter
wavelengths at the blue end than
light of longer wavelengths at the red end. Thus, when
sunlight passes through the atmosphere, the fine
particles in the air scatter blue colour (shorter
wavelengths) more strongly than red. The scattered blue
light enters our eyes, and hence, the clear sky appears
blue.
Sun appears reddish at sunrise: At the time of sunrise
and sunset, when the Sun is near the horizon, sunlight
travels a greater distance through the atmosphere to
reach us. During this, most of the shorter wavelengths
present in it are scattered away from our line of sight by
the molecules of air and other fine particles in the
atmosphere. So, light reaching us directly from the rising
or setting Sun consists mainly of the longer wavelength
red colour because of which the Sun appears red. Thus,
at sunrise and sunset, the Sun as well as the surrounding
OR
36. Explain with the help of a figure, the ring system of wiring in domestic wiring.
It consists of a ring-circuit. Wires starting from the main fuse-box run around all the main rooms of the house and then come back to the fuse-box again. The fuse-box contains a fuse of rating about 30A. A separate connection is taken from the live wire of the ring for each appliance. The terminal of the appliance is connected to the live wire through a separate fuse and a switch. If the fuse of one appliance burns, it does not affect the other appliances. For each appliance, the wires used for connection should be of proper current carrying capacity.
37.Draw the structure for the following compounds:
a. Propanoic acid c. Fluoropentane
b. Hexanone d. Benzene e. Butanal
Butanal
Benzene
Propanoic acid
Hexanone
Fluoropentane
38.Explain pH scale and importance of pH scale in daily life.
There is lot of importance of pH in everyday life of an human being as well as plants :The value of the pH for the human body is in the range of 7 to 7.8. This range shows the importance of pH in everyday life which makes an important statement about the kind of environment we would like to be in. The pH of the rain water could also be measured and it is experimentally found that most of the rainfall for the first 10 -15 minutes is acidic in nature. If the value of the pH is found to be less than the value 5.6 then the rain is thought to be acidic. Acidic rains is highly damaging in nature. The acidic rain effect is evident for architectural marvel of the world the Taj Mahal. The main cause of this is the Mathura Oil refinery and many of the factories that has come up in the vicinity of Taj.The air in the surrounding areas are polluted and are filled with gaseous particles responsible for such type of rain. This type of rain could cause damage to the crops as well and change the pH of crop field soil profile.
Even in our digestive system, particularly the stomach, contains digestive juices or acids that help in the process of digestion and since the process of digestion is very important one the pH plays a big role in maintaining the neutral atmosphere of the stomach.
During this process of digestion a lot of acids are also secreted in the stomach. These acids if not neurtralised on time could damage the inner linings of the stomach and food pipe as well.
To neutralize the acids that are produced, some bases needs to be added. These bases are taken externally in the form of tablets and syrups which are basically nothing but diluted form alkaline suspension like milk of magnesia.
So, the importance of pH in everyday life is immense. The presence of pH in mouth is also important. This pH value is roughly around 5.5. Once the food is taken in and pushed through food pipe there are still some particles of food remaining in the mouth cavity.
The bacteria present in the mouth starts breaking down these food particles and while doing so produce acids which usually damage the teeth or trigger the teeth decay teeth.The human teeth are made up of a material that is the hardest in nature, and is not corroded by any substance. But when these teeth are exposed to the acids generated by the bacteria they are prone to tooth decay.
This can be prevented if one is a bit careful. Wash and rinse mouth thoroughly after taking food. Mouth wash could also be used. The teeth can be brushed twice a day and this helps a lot in preventing the tooth decay. In order to neutralise the effect of mouth cavity acid build up the tooth pastes are found to be basic in nature.
OR
38.What do all acids and all bases have in common?
Most strong acids and bases are both corrosive in nature. They tend to corrode or rust metals.Both, acids and bases change the colour of litmus paper. An acid changes the colour of a blue litmus paper to red and a base changes the colour of red litmus paper to blue.Strong acids can damage the skin causing severe burns if it gets into contact with the skin. But did you know, even strong bases can do the same?A lot of common things that are used in day-to-day basis are acids and bases. For e.g. Citric fruits such as lemon, orange, grapefruit, etc contain citric acid and tamarind, grapes, etc contain tartaric acid, olive oil contains oleic acid and vinegar contains acetic acid. Many soaps, toothpaste, etc have bases in them. Baking soda is also basic in nature.Both are classified on the basis of strength, concentration and their respective basicity and acidity. Acids are also classified on the basis of source and the presence of oxygen.Acids and bases both react with water and a lot of acids and bases are soluble in nature.Both acids and bases are electrolytes which means that they’re good conductors of electricity.Acids and bases both produce ions in water solution. Acids release hydrogen ions (H+) whereas Bases release hydroxide ions (OH–).The process of mixing acid or a base in water is an exothermic one that releases some amount of heat.
38.Explain strength of acid and base solution.
Strong Acids
Strong acids completely dissociate in water, forming H+ and an anion. There are six strong acids. The others are considered to be weak acids. You should commit the strong acids to memory:
HCl: hydrochloric acid
HNO3: nitric acid
H2SO4: sulfuric acid
HBr: hydrobromic acid
HI: hydroiodic acid
HClO4: perchloric acid
If the acid is 100 percent dissociated in solutions of 1.0 M or less, it is called strong. Sulfuric acid is considered strong only in its first dissociation step; 100 percent dissociation isn't true as solutions become more concentrated.
H2SO4-→ H+ + HSO4+2
Weak Acids
A weak acid only partially dissociates in water to give H+ and the anion. Examples of weak acids include hydrofluoric acid, HF, and acetic acid, CH3COOH. Weak acids include:
Molecules that contain an ionizable proton. A molecule with a formula starting with H usually is an acid.
Organic acids containing one or more carboxyl group, -COOH. The H is ionizable.
Anions with an ionizable proton
(e.g., HSO4- → H+ + SO42-).
Cations
Transition metal cations
Heavy metal cations with high charge
NH4+ dissociates into NH3 + H+
Strong Bases
Strong bases dissociate 100 percent into the cation and OH- (hydroxide ion). The hydroxides of the Group I and Group II metals usually are considered to be strong bases.
LiOH: lithium hydroxide
NaOH: sodium hydroxide
KOH: potassium hydroxide
RbOH: rubidium hydroxide
CsOH: cesium hydroxide
*Ca(OH)2: calcium hydroxide
*Sr(OH)2: strontium hydroxide
*Ba(OH)2: barium hydroxide
* These bases completely dissociate in solutions of 0.01 M or less. The other bases make solutions of 1.0 M and are 100 percent dissociated at that concentration. There are other strong bases than those listed, but they are not often encountered.
Weak Bases
Examples of weak bases include ammonia, NH3, and diethylamine, (CH3CH2)2NH. Like weak acids, weak bases do not completely dissociate in aqueous solution.
Most weak bases are anions of weak acids.
Weak bases do not furnish OH- ions by dissociation. Instead, they react with water to generate OH- ions.
39. Explain force on a current carrying conductor in a Magnetic Field.
Theory:
A current carrying conductor placed in a magnetic field experiences a force. If the direction of the field and that of current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both and that can be determined using the Fleming’s left-hand rule. When current establishes in the conductor, it gets displaced which verifies the existence of a force on the conductor.
Fig. (1) - A current-carrying rod, AB, experiences a force perpendicular to its length and the magnetic field
Fleming's Left Hand Rule:
Hold the thumb and the first two fingers of your left hand mutually at right angles to each other as shown in Fig. (1). Then if the Forefinger points in the direction of the Field, and the second finger in the direction of the Current, the thumb will point in the direction of Force
Comments
Post a Comment