Question
State the advantages and disadvantages of using solar cells.
✓
Answer
Advantage of solar cell.
- They have no moving parts and require no maintenance.
- They can be set up in remote and inaccessible areas.
- They are very expensive.
- They are less efficient. They can convert only about 25% of light falling on them into electricity.
- They cannot work during night time.
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(Cultural, agriculture, fire, brain, Cro-Magnon, Homo sapiens, Neanderthal)
Evolution of upright man continued in the direction of developing its ………. for the period of about 1 lakh years and meanwhile he discovered the ………. Brain of man, 50 thousand years ago had been sufficiently evolved to the extent that it could be considered as member of the species ………… Neanderthal man can be considered as the first example of wise-man. The ……….. man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier. About 10 thousand years ago, wise-man started to practise the ………. It started to rear the cattle-herds and established the cities. ………..development took place later.
Evolution of upright man continued in the direction of developing its ………. for the period of about 1 lakh years and meanwhile he discovered the ………. Brain of man, 50 thousand years ago had been sufficiently evolved to the extent that it could be considered as member of the species ………… Neanderthal man can be considered as the first example of wise-man. The ……….. man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier. About 10 thousand years ago, wise-man started to practise the ………. It started to rear the cattle-herds and established the cities. ………..development took place later.
Depending on electronic configuration the properties of the elements vary in different groups. Explain why?
In cold regions in winter, the rocks crack due to anomalous expansion of water.
Write short notes: Lamarckism.
Observe the following figure and write the answer of the question.
- Which process is shown in the figure?
- Explain the chemical reaction shown in the figure.
- Write the reactions on anode and cathode.
Taking into consideration the period of the elements given below, answer the following questions:
i. Arrange the above elements in a decreasing order of their atomic radii.
ii. State the period to which the above elements belong.
iii. Why this arrangement of elements is similar to the above period of the modern periodic table?
iv. Which of the above elements have the biggest and the smallest atom?
v. What is the periodic trend observed in the variation of atomic radius while going from left to right within a period?
| Element | Atomic radius (pm) |
| O | 66 |
| B | 88 |
| C | 77 |
| N | 74 |
| Be | 111 |
| Li | 152 |
ii. State the period to which the above elements belong.
iii. Why this arrangement of elements is similar to the above period of the modern periodic table?
iv. Which of the above elements have the biggest and the smallest atom?
v. What is the periodic trend observed in the variation of atomic radius while going from left to right within a period?
In a Std. X class, out of 40 students, 10 students use spectacles, 2 students have ( positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
What do you understand by the term ‘evolution’? State Darwin’s theory of evolution.
Draw the diagram of a DC generator. Then explain as to how the DC current is obtained.
(translation, anticodon, tRNA, mRNA, amino acids, triplet codon, transcription, DNA)
The …….. formed in nucleus comes in cytoplasm. It brings in the coded message from DNA. The message contains the codes for amino acids. The code for each amino acid consists of three nucleotides. It is called as ‘………..’. Each mRNA is made up of thousands of triplet codons. As per the message on mRNA, ……… are supplied by the ………. For this purpose, tRNA has ‘…………’ having complementary sequence to the codon on mRNA. This is called ‘………..’.
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