CBSE ADDA

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

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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 -

Rational Numbers test paper for class 08 Mathematics. These test papers include all main concepts of the chapter in CBSE class 08 Mathematics. It is very useful for testing and commanding over the topic and to excel in various Olympiads and other competitions  Introduction  Properties of Rational Numbers  Representation of Rational Numbers on the Number line.  Rational Numbers between two rational numbers. Learning Objectives:  The students learn to represent rational numbers on the number line. They learn to verify various properties taking different values. 8th maths Rational Number CBSE Test Paper - 01 8th maths Rational Number CBSE Test Paper - 02 8th maths Rational Number CBSE Test Paper - 03 8th maths Rational Number CBSE Test Paper - 04 8th maths Rational Number CBSE Test Paper - 05 Download Files 8th maths Rational Number CBSE Worksheet - 01 8th maths Rational Number CBSE Worksheet - 02 8th maths Rational Number CBSE Worksheet - 03 8th maths Rational