When an object is charged by rubbing it against another object, the two objects acquire opposite charges. (b) becomes positively charged while the cloth has a negative charge. (d) Becomes negatively charged while the cloth has a positive charge.Īns. (c) And the cloth both acquire negative charge. (b) Becomes positively charged while the cloth has a negative charge. (a) And the cloth both acquire positive charge. When a glass rod is rubbed with a piece of silk cloth the rod As copper is a highly conducting material, it cannot be charged easily by friction.Ģ. Charging by friction is used to charge only non-conducting materials (poor conductors of electricity). When insulating materials such as plastic scales, balloons, and woollen clothes rub against each other, they may become electrically charged. Which of the following cannot be charged easily by friction? Laws describe the patterns we see in large amounts of data, but do not describe why the patterns exist.1. A law is a relationship that exists between variables in a group of data. If the temperature of the gas is increased, the volume of the gas increased. These scientists found, after many, many tests, that certain patterns existed in the observations on gas behavior. As a comparison, theories explain why we observe what we do and laws describe what happens.įor example, around the year 1800, Jacques Charles and other scientists were working with gases to, among other reasons, improve the design of the hot air balloon. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics. Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. To be a scientific theory carries a lot of weight it is not just one person's idea about something The phrase "just a theory" has no room in science. In order for a theory to change, there must be many observations or pieces of evidence that the theory cannot explain. Theories can change, but it is a long and difficult process. They have a large amount of support and are able to satisfactorily explain numerous observations. They are explanations as to why we observe something. They aren't predictions (although we may use theories to make predictions). Theories are explanations of natural phenomena. Note some key features of theories that are important to understand from this description: But the phenomenon of gravity, like evolution, is an accepted fact. Our understanding of gravity is still a work in progress. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter (stating that everything is made of atoms) or the germ theory of disease (which states that many diseases are caused by germs). Such fact-supported theories are not "guesses" but reliable accounts of the real world. "A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Theories also allow scientists to make predictions about as yet unobserved phenomena." In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. In everyday language a theory means a hunch or speculation. The explanation becomes a scientific theory. "Some scientific explanations are so well established that no new evidence is likely to alter them. The United States National Academy of Sciences describes what a theory is as follows:
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