A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio R/R′ is –
(a) 1/25 (b) 1/5 (c) 5 (d) 25
(d) Resistance of a piece of wire is proportional to its length. A piece of wire has a resistance R. The wire is cut into five equal parts.
Therefore, resistance of each part =
All the five parts are connected in parallel. Hence, equivalent resistance (R’) is given as
Therefore, the ratio is 25.
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?
Why are traits acquired during the life-time of an individual not inherited?
How many structural isomers can you draw for pentane?
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?
Oil and fat containing food items are flushed with nitrogen. Why?
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Draw a labelled diagram of the longitudinal section of a flower.
Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?