In the Current Electricity section, you learned about electric charge, current, voltage and other related topics. But, just because you have a voltage does not mean electric current will flow. Electrons also need a complete loop of conductive material to flow, called a closed circuit . Let's look at a light switch. When you turn the switch "on", the switch creates a path that conducts electricity and electrons start to move—meaning electric current flows—and the light turns on. As soon as you turn the switch "off", the path is broken and electrons can no longer flow. The switch is like a drawbridge; switching it on is letting down the bridge so the electrons can cross (just like cars crossing a bridge) and provide energy to the light bulb. Illustration of how electric current can move through a closed loop of conductive material (left figure) but stops flowing whenever the loop is broken (right figure). This figure shows how a light bulb l...
NUMBER SYSTEMS In Hindu Arabic System, we use ten symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 called digits to represent any number. This is the decimal system where we use the numbers 0 to 9. 0 is called insignificant digit. A group of figures, denoting a number is called a numeral. For a given numeral, we start from extreme right as Unit’s place, Ten’s place, Hundred’s place and so on. We represent the number 309872546 as shown below: 6-units 4-Tens 5-Hundreds 2-Tounsands 7-Ten thousand 8-Lacs 9-Ten lacs(million) 0-Crocres 3-Ten croces We read it as “Thirty crores, ninety- eight lacs, seventy-two thousands five hundred and forty-six.” In this numeral: The place value of 6 is 6 ×1 = 6 The place value of 4 is 4 ×10 = 40 The place value of 5 is 5 ×100 = 500 The place value of 2 is2 ×1000 = 2000 and so on. The face value of a digit in a numbers is the value itself wherever it may be. Thus, the face value of 7 in the above num...
Introduction to the Universe Solar System The Solar System is a collection of planets, moons, asteroids and comets and other rocky objects orbiting the Sun. The Solar System is believed to extend out to at least 150 000 million km from the Sun, although the planets are all found within about 6000 million km. Our Solar System is thought to have formed 4.6 x 10 9 years ago from a vast, rotating cloud of gas and dust known as the solar nebula. As the solar nebula rotated, its gravity began to attract gas and dust towards the centre, eventually forming our Sun. The Sun The Sun is the powerhouse of the Solar System. Without it, life on Earth simply would not exist. Despite burning its hydrogen fuel for the best part of 5 billion years, the Sun is still only half way through its life cycle. The study of the Sun, its environment and how the material it discharges interacts with other worlds in the Solar System is of great interest to us all. ...
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