Why don’t two magnetic field lines intersect each other?
Two magnetic lines never intersect because if two field lines of a magnet intersect, then at the point of intersection, the compass needle points in two different directions which is not possible at same time a needle shows to different directions. Hence, they never interact.
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.
List the properties of magnetic field lines.
State Fleming’s left-hand rule.
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.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
How do Mendel’s experiments show that traits may be dominant or recessive?
Compare and contrast fossil fuels and the Sun as direct sources of energy.
How is the process of pollination different from fertilisation?
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron.
What do you mean by a precipitation reaction? Explain by giving examples.
Besides gallium, which other elements have since been discovered that were left by Mendeléev in his Periodic Table? (any two)
What type of oxides are formed when non-metals combine with oxygen?
What is the role of the seminal vesicles and the prostate gland?
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?