CBSE ADDA

Force A force is an agent which can change or try to change the state of an object. Force is the product of  mass and acceleration F = ma Force has both magnitude and direction, making it a vector quantity. The SI unit used to measure force is the Newton (symbol N), which is equivalent to kg•m•s-2 Actions like picking, opening, shutting, kicking, hitting, lifting, flicking, pushing, pulling are often used to describe certain tasks. Each of these actions usually results in some kind of change in the motion of an object. A force is a push or pull upon an object resulting from the object's interaction with another object.   Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. All forces (interactions) between objects can be placed into two broad categories: • Contact forces, and • Non Contact for

1. The current passing through a room heater has been halved. What will happen to the heat produced by it? 2. An electric iron of resistance 20 ohm draws a current of 5 amperes. Calculate the heat produced in 30 seconds. 3. An electric heater of resistance 8 ohm takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater. 4. A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination in half a minute. 5. A resistance of 25 ohm is connected to a 12 V battery. Calculate the heat energy in joules generated per minute. 6. 100 joules of heat is produced per second in a 4 ohm resistor. What is the potential difference across the resistor? 7. An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at minimum heating’ it consumes a power of 360 W but at ‘maximum heating’ it takes a power of 840 W. Ca

10 th [x] Sample papers for Summative Assessment – 1  [links]             Mathematics Science Social Science English, Hindi and Sanskrit 10 th [x] Sample papers for Summative Assessment – 2 [links] Mathematics Science Social Science English, Hindi and Sanskrit

Oxidation and reduction reactions These are reactions where electrons are transferred from one species (atom, molecule or ion) to another. We can write 'half' equations to show only what happens to the species losing electrons or a different 'half' equation to show the species gaining electrons. The whole equation is put together by making sure that the numbers of electrons are balanced in each half equation and adding them together (when the electrons will cancel out) Oxidation is a chemical process in which there is a loss of electrons. The species, which gets oxidized becomes more positive or less negative, e.g., Na   →   Na +   + e -   (Na is oxidized to Na +   ) Fe 2+   →   Fe 3+   + e -   (Fe 2+   is oxidized to Fe 3+ ) Reduction is a chemical process in which there is a gain of electrons. The species, which gets reduced becomes more negative or less positive, e.g., Cl 2   + 2e -   →   2Cl -   (Cl 2   is reduced to Cl - ) S + 2e -