Contrasting student and also scientific views
Student day-to-day experiences
You are watching: Sort the statements below by whether they are true for electric force or gravitational force.
Many college student will have experienced small but memorable electric shocks as a result of ‘static electricity’ when obtaining out of a automobile on a warm, dry day or on purpose scuffing their shoes across synthetic carpet and also touching a steel door take care of or each other. Some students will likewise have played with using ‘static electricity’ to tempt or repel very light objects, e.g. Choose up small pieces of paper or attracting their hair through a rubbed plastic comb or ruler.
Students regularly do not attach events the involve receiving an electric shock (e.g. Playing on a trampoline mat), with comparable events the involve static electrical attraction, (e.g. Observing clinging apparel that emerge from a tumble dryer or sugar grains that are attracted come the inside surface of a plastic container when shaken). For younger student these events are not connected by the typical idea of their ‘electrostatic’ origins and also student might not do this attach without encouragement.
Understandably, plenty of younger students execute not watch the should discriminate in between electrostatic forces and also magnetic forces. Come them, these appear to be common experiences that the very same non-contact force. Because that example, a balloon ‘rubbed’ through a cloth resulting in the attraction come a ceiling is frequently described confusingly by student (and some adults) together ‘magnetized’ in part way.
For countless students, the dramatic observation of a lightning discharge is just one of their most memorable experience of ‘seeing’ the impacts of the movement of huge amounts of electric charge, although this experience is frequently incorrectly meeting to various other phenomena.
Research: Benseghir & Closset (1996), Guisasola (1995), Harrington (1999), Henriques (2000), McIntyre (1974), Park, Kim, Kim & Lee (2001), Seroglou, Koumaras & Tselfes (1998)
Attraction and repulsion of electric charges is just one of three basic non-contact pressures in nature. The others are magnetism and the pressure of gravity (see the focus idea forces without contact).
There are only two different sorts of known charge which scientists have actually labelled together ‘positive’ and also ‘negative’. This names were chosen historically to suggest that they to be somehow ‘opposites’ of every other, to assist emphasise the two different observable forms. Scientists do not know exactly what fee is or how the two sorts of charge differ from one another; but each affects itself and also its opposite form.
Positive and an adverse charged objects lure or traction each other together, while similar charged objects (2 positives or 2 negatives) repel or push each other apart. The fee objects do not need to be emotional in order because that the repulsive or attractive pressures to it is in experienced between them; i.e. They have the right to be observed to impact each various other at brief distances and also without the need for any substance in between, e.g. Air.
When things made that a great electrical insulator choose plastic or glass is rubbed intensely with one more flexible electric insulator made from fur, noodle or structure it is feasible for fee of one kind to relocate from the surface of one insulator to the surface of the other. In Fig 1 below, before rubbing each item is electrically balanced. In Fig 2 below, ~ rubbing the plastic ruler has come to be negatively charged and also the noodle positively charged. The rubbing go not create charges, yet redistributes the charge in between the two objects. As a repercussion of your different as whole charge, the two surfaces as soon as separated will lure each other.
Charged objects deserve to be created by using different methods to rubbing or sliding but all require the two surfaces to be in nearby contact and then separated. Other instances are peeling two plastic sheets personally or removing adhesive tape from a sheet of glass. Fee objects will additionally influence all other tiny ‘non-charged’ objects to end up being partially oppositely charged once they are carried near come them. This reasons them to be attracted to each other. Because that example, a fee comb will attract little objects such as grains of street when carried close to them. If the seed of street come into call with the comb then in a small while several of the grains will obtain the same charge together the comb and also will be quickly repelled.
The amount of fee on the surface ar of any kind of object will gradually reduce through time together the charge is eventually carried out away by water vapour in the surrounding air. For example a charged balloon will ultimately fall from the ceiling together its fee diminishes.
Natural displays of charge motion like lightning mostly occur in storm clouds and also less frequently over erupting volcanoes or in dust storms. In storm clouds, the fee is redistributed unevenly (parts will certainly be positive and other parts negative).This imbalance can construct up to the point where air i do not care a conductor, and also the imbalance is lessened by a quick spark in ~ the cloud or to the Earth. This is the lightning flash us see. The thunder we often hear is the result of this powerful spark rapidly heating the air.
Scientists space still do the efforts to find out specifically why the imbalance of charge is created in storm clouds.
See the websites listed in the more resources ar for much more information.
Critical teaching ideasElectrostatic forces are non-contact forces; they pull or push on objects without poignant them.Rubbing some materials together can result in something called ‘charge’ being relocated from one surface to the other.Charged objects traction on other uncharged objects and also may either push or pull on various other charged objects.There space two sorts of charge; scientists carry out not know exactly what charge is or exactly how the two sorts of fee differ; they speak to the two sorts ‘positive’ and ‘negative’.Lightning is the an outcome of quick charge motions in storm clouds.
At this level, the prime focus should it is in on encouraging students to observe and also explore electrostatic phenomena v play, bring about the breakthrough of basic explanations for the it was observed attraction and also repulsion of charged objects. Students must be urged to discriminate between electrostatic forces and also magnetic pressures as various examples of non-contact forces.
The inclusion of tasks that indicate the rubbing of two similar plastic objects v the same material is important, as it is only in these instances that you have the right to see the two comparable charged objects advertise each various other apart as a display screen of the repulsion of favor charges.
A main idea because that students to recognize is the electrostatic forces are non-contact forces; that is not vital at this level to emphasize to students the ‘like charges repel and also unlike fees attract’. It is more appropriate to demonstrate that fee objects attract uncharged objects, and also can either entice or repel various other charged objects.
Try to focus student attention on everyday ‘electrostatic’ experiences. These normally involve one object being charged by rubbing and another object that has actually not. Rubbed plastic combs and rulers attracting piece of file are typically used examples however student investigations have to not be minimal to simply these.
The principles students will bring to this area room both varied and mostly not really strongly held. Using demonstrations and also asking students to predict what may occur will typically be strong approaches for identifying students’ existing ideas of electrostatics in ~ this level.
Research: Guisasola (1995), McIntyre (1974)
When there is a many moisture in the air (such as when the weather is humid, and/or the is raining) it is an extremely hard to create the electrostatic effects and also experience the results described. Arrangement to effort these tasks when the weather problems are warm and also dry.
Open up discussion via a mutual experience
Now obstacle the balloon using a item of wool/synthetic material or a jumper so that it becomes charged. Ask the students to predict what will take place if you bring the material or jumper you used to obstacle it near to the balloon.
The rubbing product will have a different charge to the balloon as charge moves native one thing to the other. The balloon and the rubbing material should traction each various other together showing an attractive force.
Now include another balloon so the it hangs near to the first. As soon as again rub each balloon through the same item of wool/synthetic material or the jumper you are wearing. They should now become similarly charged. Was standing well ago and you and the students will watch the 2 balloons different as they attempt to loss by pushing on each other.
Have the students predict if changes will take place as time passes. Will certainly the positions of the balloons change? Student should be guided to recognise the the balloons will gradually lose charge and move closer with each other as the fee decreases through time.
Challenge existing student views
Again using an inflated balloon, suspend that as prior to on a length of fine noodle or fishing line. Perform not effort to obstacle or charge the balloon in any kind of way. Now ask the students come predict what will happen when you bring a bar magnet near to the balloon.
It is valuable to accept any kind of suggestions around different methods of pass the magnet close to the balloon (e.g. “Try the magnet the other method round.” “Hold it level near the balloon.”). It is probable that countless students will predict the balloon and also magnet will be attractive (and therefore will likely want to shot the magnet near the balloon in various ways once they very first see no effect). However very few students will have any kind of reasons to support this prediction – for many students, attraction is predicted since they have not ever differentiated magnetic and electrostatic forces. Execute not usage a fee balloon due to the fact that it will certainly be attracted to most uncharged objects and this may wrongly reinforce the student’s predictions.
Provide an open difficulty to be explored via beat or through trouble solving
Give a balloon to every member of the class. An obstacle the student to do their balloon continue to be attracted to the ceiling for the longest time. Students will must inflate and charge their balloon selecting one of a variety of synthetic materials noted for the purpose. Consider having the college student measure the moment with stopwatches approximately the point at i m sorry the balloons fall.
Encourage students to think around the following to achieve success:How large should castle inflate the balloon? will certainly it make any type of difference?What kind of product should they usage to obstacle (charge) your balloon?How long should they try to obstacle or charge the balloon prior to their attempt?What shape of balloon have to they pick – one or sausage shaped? will certainly this do a difference?
Approaches to this activity can vary. Students may select to play with the materials and also discuss your experiences later. They may additionally be motivated to select one question and explore this systematically.
Provide a range of artificial materials and also natural materials like fur and also cotton offcuts for the students to choose from and trial. Consider also using circular and sausage shaped balloons.
Open conversation via a mutual experience
Another demonstration the will present the same effects as the balloons needs two clean plastic rulers and a little plastic party (water or soft drink – a bottle through a lid that is 2-3 centimetres wide). Rub one ruler with structure (if you room wearing a woollen jumper, rubbing the ruler conveniently under your armpit is really effective), and balance the on the bottle lid. Now rub the various other ruler, and also bring the rubbed finish of this 2nd ruler close to to the rubbed finish of the very first ruler. You will see the ruler on the drink bottle turn away indigenous the second ruler due to the fact that the two rulers are similarly charged and also push each various other away. If you lug the oppositely fee ‘rubbed’ wool near one the the rulers they will lure each other.
One way of stimulating discussion would be to show this activity and then challenge students to discover connections come the task involving charging 2 balloons above.
Focus students’ fist on overlooked detail
Collect a wide selection of straightforward household items whereby electrostatic pressures can be viewed to it is in in operation. These have the right to be explored in the great with tiny groups the students.
See more: Nyro, Laura Nyro More Than A New Discovery Lp, More Than A New Discovery
Clarifying and also consolidating principles for interaction to others
Following the students’ investigate of family items they can then be motivated to report ago to the class on their findings. This can be excellent using brief presentations i m sorry identify any related monitoring of electrostatic pressures in action. The investigation might be prolonged to encompass students writing brief sentences relenten what they observe and also drawing labelled diagrams of the items and also the it was observed effects. Students can be request to discover examples the electrostatic experience at home which can be common at school. It might be advantageous if student can bring pictures or illustrations they might share.