Ask questions which are clear, concise and easy to understand.
Ask QuestionPosted by Manauwarali Ansari 5 years, 8 months ago
- 1 answers
Posted by Afser Reyaz 5 years, 8 months ago
- 1 answers
Posted by Ak Aastha 5 years, 8 months ago
- 1 answers
Meghna Thapar 5 years, 8 months ago
When a girl is born, the ovaries already contain thousands of immature eggs. On reaching puberty, some of these start maturing. One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube. The two oviducts unite into an elastic bag-like structure known as the uterus. The uterus opens into the ****** through the cervix. The sperms enter through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they may encounter the egg. The fertilised egg, the zygote, gets implanted in the lining of the uterus, and starts dividing.
The release of an ovum from an ovary is called ovulation. In human females, the ovaries start releasing ovum once every 28 days from the age of puberty. Fertilisation is possible if mating takes place during the middle of menstrual cycle because in a normal healthy girl the ovulation takes place on the 14th day of the beginning of menstrual cycle of 28 days. The embedding of embryo in the thick lining of the uterus is called implantation.
The lining thickens and is richly supplied with blood to nourish the growing embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta.
Placenta is a disc like special tissue which develops between the uterus wall and the embryo after implantation. Its function is the exchange of nutrients, oxygen and waste products between the embryo and the mother. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta. The time period from the fertilisation up to the birth of a baby is called gestation. The average gestation period in humans is about 9 months (about 38 weeks).The child is born as a result of rhythmic contractions of the muscles in the uterus.
Posted by Rajan Raghav 5 years, 8 months ago
- 1 answers
Sanaya Sharma ???? 5 years, 8 months ago
Posted by Nithish Waran 5 years, 8 months ago
- 2 answers
Meghna Thapar 5 years, 8 months ago
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light travels through the material. It is defined as. where c is the speed of light in vacuum and v is the phase velocity of light in the medium.
Posted by Sanaya Sharma ???? 5 years, 8 months ago
- 8 answers
??(｡☬Ashu☬｡)?? Bhardwaj 5 years, 8 months ago
Posted by Sonu Khan Fez 5 years, 8 months ago
- 2 answers
Posted by Muskan Sidhu 5 years, 8 months ago
- 1 answers
????? ?????? 5 years, 8 months ago
Posted by ???Queen*****P.Y.K ??? 5 years, 8 months ago
- 1 answers
Posted by Salomi Edward 5 years, 8 months ago
- 40 answers
Salomi Edward 5 years, 8 months ago
????? ?????? 5 years, 8 months ago
????? ?????? 5 years, 8 months ago
????? ?????? 5 years, 8 months ago
Posted by Praveen Prasad 5 years, 8 months ago
- 1 answers
Vishu Chauhan 5 years, 8 months ago
Posted by Praveen Prasad 5 years, 8 months ago
- 1 answers
??? ??? 5 years, 8 months ago
Posted by ???Queen*****P.Y.K ??? 5 years, 8 months ago
- 5 answers
Posted by ♛?????♛ . Developer . 5 years, 8 months ago
- 4 answers
Posted by Garvit Gandhi 5 years, 8 months ago
- 1 answers
Meghna Thapar 5 years, 8 months ago
Electric generator is based on the phenomena of electromagnetic induction.
In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity.
Posted by Junaid Malik 5 years, 8 months ago
- 1 answers
Posted by ??? ??? 5 years, 8 months ago
- 4 answers
Meghna Thapar 5 years, 8 months ago
The fossils provide evidence of evolution. For example, a fossil bird called Archaeopteryx looks like a bird but it has many features which are found in reptiles. This is because Archaeopteryx has feathered wings like those of birds but teeth and tail like those of reptiles. Therefore, Archaeopteryx is a connecting link between the reptiles and birds and suggests that birds have evolved from reptiles. Thus, fossils provide evidence that the present plants and animals have originated from the previously existing ones through the process of continuous evolution.
??(｡☬Ashu☬｡)?? Bhardwaj 5 years, 8 months ago
Posted by Junaid Malik 5 years, 8 months ago
- 1 answers
Posted by ??(｡☬Ashu☬｡)?? Bhardwaj 5 years, 8 months ago
- 41 answers
????? ?????? 5 years, 8 months ago
??(｡☬Ashu☬｡)?? Bhardwaj 5 years, 8 months ago
????? ?????? 5 years, 8 months ago
Meghna Thapar 5 years, 8 months ago
- AC generator producing a current which periodically changes its direction
- DC generator producing a current which always flows in the same direction.
An AC generator can be changed into a DC generator by replacing the slip-ring arrangement with the split-ring (commutator) arrangement.
????? ?????? 5 years, 8 months ago
Grahul 📒🎒📓📔🙇🙇🙇 Rahul 5 years, 8 months ago
Salomi Edward 5 years, 8 months ago
Posted by Rohit Shah 5 years, 8 months ago
- 5 answers
Meghna Thapar 5 years, 8 months ago
- Autotrophs can prepare their own food from simple inorganic sources like carbon dioxide and water. Example - green plants and some bacteria.
Posted by Leepaxi Diwan? 5 years, 8 months ago
- 1 answers
Meghna Thapar 5 years, 8 months ago
In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. An electric generator consists of a rotating rectangular coil ABCD placed between the two poles of a permanent magnet. The two ends of this coil are connected to the two rings R1 and R2. The inner side of these rings are made insulated. The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2, respectively. The two rings R1 and R2 are internally attached to an axle. The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field.
Outer ends of the two brushes are connected to the galvanometer to show the flow of current in the given external circuit. When the axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet. Let us say the coil ABCD is rotated clockwise. By applying Fleming’s right-hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD. If there are larger numbers of turns in the coil, the current generated in each turn adds up to give a large current through the coil.
This means that the current in the external circuit flows from B2 to B1. After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms change, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective armschanges. Such a current, which changes direction after equal intervals of time, is called an alternating current (abbreviated as AC). This deviceis called an AC generator.
Posted by Leepaxi Diwan? 5 years, 8 months ago
- 2 answers
Meghna Thapar 5 years, 8 months ago
An electric motor is a rotating device that converts electrical energy to mechanical energy. Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3 players etc. An electric motor consists of a rectangular coil ABCD of insulated copper wire. The coil is placed between the two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. The ends of the coil are connected to the two halves P and Q of a split ring. The inner sides of these halves are insulated and attached to an axle. The external conducting edges of P and Q touch two conducting stationary brushes X and Y, respectively. Current in the coil ABCD enters from the source battery through conducting brush X and flows back to the battery through brush Y. Notice that the current in arm AB of the coil flows from A to B. In arm CD it flows from C to D, that is, opposite to the direction of current through arm AB. On applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. The force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards. Thus the coil and the axle O, mounted free to turn about an axis, rotate anti-clockwise. At half rotation, Q makes contact with the brush X and P with brush Y. Therefore the current in the coil gets reversed and flows along the path DCBA. A device that reverses the direction of flow of current through a circuit is called a commutator. In electric motors, the split ring acts as a commutator. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was earlier pushed down is now pushed up and the arm CD previously pushed up is now pushed down. Therefore the coil and the axle rotate half a turn more in the same direction. The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and to the axle.
Meghna Thapar 5 years, 8 months ago
In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. An electric generator consists of a rotating rectangular coil ABCD placed between the two poles of a permanent magnet. The two ends of this coil are connected to the two rings R1 and R2. The inner side of these rings are made insulated. The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2, respectively. The two rings R1 and R2 are internally attached to an axle. The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field.
Outer ends of the two brushes are connected to the galvanometer to show the flow of current in the given external circuit. When the axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet. Let us say the coil ABCD is rotated clockwise. By applying Fleming’s right-hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD. If there are larger numbers of turns in the coil, the current generated in each turn adds up to give a large current through the coil.
This means that the current in the external circuit flows from B2 to B1. After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms change, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective armschanges. Such a current, which changes direction after equal intervals of time, is called an alternating current (abbreviated as AC). This deviceis called an AC generator.
Posted by ꧁༺★King K. Tyagi Ji}★༺꧂ ??? 5 years, 8 months ago
- 4 answers
Posted by Bunny Singhania 5 years, 8 months ago
- 1 answers
Posted by Salomi Edward 5 years, 8 months ago
- 4 answers
Posted by Hemant Sharma 5 years, 8 months ago
- 2 answers
Posted by Tina ? 5 years, 8 months ago
- 2 answers
Rounak Srivastav 5 years, 8 months ago
Posted by Jyoti Yadav 5 years, 8 months ago
- 1 answers
Meghna Thapar 5 years, 8 months ago
Extraction of Less Reactive Metals:
The less reactive metals are extracted by the reduction of their oxides by heat alone.
Example: Mercury (II) sulphide ore is roasted in air when mercury (II) oxide is formed. When this mercury (II) oxide is heated to about 300° C, it decomposes to form mercury metal.
Extraction of Moderately Reactive Metals:
The moderately reactive metals in the middle of the reactivity series are extracted by the reduction of their oxides with carbon, aluminium, sodium or calcium.
It is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides. So, before reduction can be done, the ore is converted into a metal oxide. The concentrated ores can be converted into metal oxides by the process of calcination or roasting.
Extracting Metals towards the Top of the Activity Series:
Metals high up in the reactivity series are very reactive. These metals have a strong affinity for oxygen. So, oxides of sodium, magnesium, calcium and aluminium cannot be reduced by carbon.
These metals are obtained by electrolytic reduction.
Posted by Tina ? 5 years, 8 months ago
- 2 answers
????? ?????? 5 years, 8 months ago
myCBSEguide
Trusted by 1 Crore+ Students
Test Generator
Create papers online. It's FREE.
CUET Mock Tests
75,000+ questions to practice only on myCBSEguide app
????? ?????? 5 years, 8 months ago
0Thank You