Can any source of energy be pollution-free? Why or why not?
Yes , no source of energy can be pollution-free. They might cause adverse effects on the environment to some extent. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly.
Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
State Fleming’s left-hand rule.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
What are the components of the transport system in highly organised plants?
Explain the terms analogous and homologous organs with examples.
Where do plants get each of the raw materials required for photosynthesis?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
What is an homologous series? Explain with an example.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?