For example, a charged comb will attract small objects such as grains of sugar when brought close to them.
This causes them to be attracted to each other. Charged objects will also influence all other small ‘non-charged’ objects to become partially oppositely charged when they are brought near to them. Other examples are peeling two plastic sheets apart or removing adhesive tape from a sheet of glass. As a consequence of their different overall charge, the two surfaces when separated will attract each other.Ĭharged objects can be created by using alternative methods to rubbing or sliding but all need the two surfaces to be in close contact and then separated. The rubbing does not create charges, but redistributes the charge between the two objects. In Fig 2 below, after rubbing the plastic ruler has become negatively charged and the cotton positively charged. In Fig 1 below, before rubbing each item is electrically balanced. When an object made of a good electrical insulator like plastic or glass is rubbed vigorously with another flexible electrical insulator made from fur, cotton or wool it is possible for charge of one type to move from the surface of one insulator to the surface of the other. they can be observed to affect each other at short distances and without the need for any substance in between, e.g. The charged objects do not need to be touching in order for the repulsive or attractive forces to be experienced between them i.e. Positive and negative charged objects attract or pull each other together, while similar charged objects (2 positives or 2 negatives) repel or push each other apart. Scientists do not know exactly what charge is or how the two sorts of charge differ from one another however each affects itself and its opposite form. These names were chosen historically to indicate that they were somehow ‘opposites’ of each other, to help emphasise the two different observable forms. There are only two different sorts of known charge which scientists have labelled as ‘positive’ and ‘negative’. The others are magnetism and the force of gravity (see the focus idea Research: Benseghir & Closset (1996), Guisasola (1995), Harrington (1999), Henriques (2000), McIntyre (1974), Park, Kim, Kim & Lee (2001), Seroglou, Koumaras & Tselfes (1998) Scientific viewĪttraction and repulsion of electric charges is one of three fundamental non-contact forces in nature. For example, a balloon ‘rubbed’ with a cloth resulting in its attraction to a ceiling is frequently described confusingly by students (and some adults) as ‘magnetized’ in some way.įor many students, the dramatic observation of a lightning discharge is one of their most memorable experiences of ‘seeing’ the effects of the movement of large amounts of electrical charge, although this experience is often incorrectly attributed to other phenomena. To them, these appear to be common experiences of the same non-contact force. Understandably, many younger students do not see the need to discriminate between electrostatic forces and magnetic forces. For younger students these events are not connected by the common idea of their ‘electrostatic’ origins and student may not make this link without encouragement. observing clinging clothes that emerge from a tumble dryer or sugar grains that are attracted to the inside surface of a plastic container when shaken). playing on a trampoline mat), with similar events that involve static electric attraction, (e.g.
Students often do not link events that involve receiving an electric shock (e.g. picking up small pieces of paper or attracting their hair with a rubbed plastic comb or ruler. Some students will also have played with using ‘static electricity’ to attract or repel very light objects, e.g. Many students will have experienced small but memorable electric shocks as a result of ‘static electricity’ when getting out of a car on a warm, dry day or deliberately scuffing their shoes across synthetic carpet and touching a metal door handle or each other. These meanings are often very closely linked with particular experiences. Students have many experiences such as putting batteries in devices correctly and ‘recharging’ batteries that have gone ‘flat’ that lead students to construct meanings for these terms. Contrasting student and scientific viewsĬontrasting student and scientific views Student everyday experiences.The 2202-20 is also designed with a green "Power On" indicator light so you know the voltage detector is working properly before use.
The durable tip allows for easy checking of power outlets. With a built in bright LED work light the 2202-20 is two tools in one. The 2202-20 can detect between -Volt AC and has an industry leading safety rating of CAT IV 1000-Volt. The Milwaukee 2202-20 Voltage Detector with LED is used for residential, commercial and industrial applications.
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