Which sources produce alternating current?
AC generators, power plants are sources that produce alternating current.
The magnetic field in a given region is uniform. Draw a diagram to represent it.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south (b) towards east
(c) downward (d) upward
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Draw magnetic field lines around a bar magnet.
State Fleming’s left-hand rule.
List the properties of magnetic field lines.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
Oil and fat containing food items are flushed with nitrogen. Why?
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Define the principal focus of a concave mirror.
Explain the mechanism of the cleaning action of soaps.
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
What is a balanced chemical equation? Why should chemical equations be balanced?
Why are some patients of diabetes treated by giving injections of insulin?
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.