What causes a compass to behave as it does

what causes a compass to behave as it does

Magnet and Magnetism

A magnet is a rock or a piece of metal that can pull certain types of metal toward itself. The force of magnets, called magnetism, is a basic force of nature, like electricity and gravity. Magnetism works over a distance. This means that a magnet does not have to be touching an object to pull it. The probing questions go deeper into understanding the underlying causes of the issue or behavior being discussed. Do not overload the discussion guide with too many questions. A FGD will generally last for 1 to 2 hours and an in-depth interview is usually shorter.

Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Surface tension is what allows heavier than water i. At liquidair interfaces, surface tension results from the greater attraction of liquid molecules to each other due to cohesion than to the molecules in the air due to adhesion. There are two primary mechanisms in play. One is an inward force on the surface molecules causing the liquid to contract.

The net effect is the liquid behaves as if its surface were covered with a stretched elastic membrane. But this analogy must not be taken too far as the tension in an elastic membrane is dependent on the amount of deformation of the membrane while surface tension is an inherent property of the liquid air or liquid vapour interface.

Because of the relatively high attraction of water molecules to each other through a web of hydrogen bondswater has a higher surface tension Surface tension is an important factor in the phenomenon of capillarity.

Surface tension has the dimension of force per unit lengthor of energy per unit area. In materials sciencesurface tension is used for either surface stress or surface energy. Due to the cohesive forces a molecule is pulled equally in every direction by neighbouring liquid molecules, resulting in a net force of zero. The molecules at the surface do not have the same molecules on all sides of them and therefore are pulled inward. This creates some internal pressure and forces liquid surfaces to contract to the minimum area.

There is also a tension parallel to the surface at the liquid-air interface which will resist an external force, due to the cohesive nature of water molecules. The forces of attraction acting between the molecules of same type are called cohesive forces while those acting between the molecules of different types are called adhesive forces.

The balance between the cohesion of the liquid and its adhesion to the material of the container determines the degree of wettingthe contact angle and the shape of meniscus. When cohesion dominates specifically, adhesion energy is less than half of cohesion energy the wetting is low what causes a compass to behave as it does the meniscus is convex at a vertical wall as for mercury in a glass container. On the other hand, when adhesion dominates adhesion energy more than half of cohesion energy the wetting is high and the similar meniscus is concave as in water in a glass.

Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the imbalance in cohesive forces of the surface layer. In the absence of other forces, drops of virtually all liquids would be approximately spherical. The spherical shape minimizes the necessary "wall tension" of the surface layer according to Laplace's law. Another way to view surface tension is in terms of energy. A molecule in contact with a neighbor is in a lower state of energy than if it were alone.

The interior molecules have as many neighbors as they can possibly have, but the boundary molecules are missing neighbors compared to interior molecules and therefore have a higher energy. For the liquid to minimize its energy state, the number of higher energy boundary molecules must be minimized.

The minimized number of boundary molecules results in a minimal surface area. Since any curvature in the surface shape results in greater area, a higher energy will also result.

Water striders stay atop the liquid because of surface tension. Lava lamp with interaction between dissimilar liquids: water and liquid wax. Photo showing the " tears of wine " phenomenon. Surface tension is visible in other common phenomena, especially when surfactants are used to decrease it:. Its SI unit is newton per meter but the cgs unit of dyne per centimeter is also used.

For example, [7]. In the illustration on the right, the rectangular frame, composed of three unmovable sides black that form a "U" shape, and a fourth movable side blue that can slide to the what to answer in tell me about yourself. Surface tension will pull the blue bar to the left; the force F required to hold the movable side is proportional to the length L of the immobile side.

We therefore define the surface tension as. This can be easily related to the previous definition in terms of force: [8] if F is the force required to stop the side from starting to slide, then this is also the force that would keep the side in the state of sliding at a constant speed by Newton's Second Law.

But if the side is moving to the right in the direction the force is appliedthen the surface area of the stretched liquid is increasing while the applied force is doing work on the liquid. This means that increasing the surface area increases the energy of the film. This what information goes on a comp card W is, by the usual argumentsinterpreted as being stored as potential energy. Consequently, surface tension can be also measured in SI system as joules per square meter and in the cgs system as ergs per cm 2.

Since mechanical systems try to find a state of minimum potential energya free droplet of liquid naturally assumes a spherical shape, which has the minimum surface area for a given volume. The equivalence of measurement of energy per unit area to force per unit length what causes a compass to behave as it does be proven by dimensional analysis. If no force acts normal to a tensioned surface, the surface must remain flat.

But if the pressure on one side of the surface differs from pressure on the other side, the pressure difference times surface area results in a normal force. In order for the surface tension forces to cancel the force due to pressure, the surface must be curved. The diagram shows how surface curvature of a tiny patch of surface leads to a net component of surface tension forces acting normal to the center of the patch.

When all the forces are balanced, the resulting equation is known as the YoungLaplace equation : [10]. The quantity in parentheses on the right hand side is in fact twice the mean curvature of the surface depending on normalisation. Solutions to this equation determine the shape of water drops, puddles, menisci, soap bubbles, and all other shapes determined by surface tension such as the shape of the impressions that a water strider's feet make on the surface of a pond.

The table below shows how the internal pressure of a water droplet increases with decreasing radius. For not very small drops the effect is subtle, but the pressure difference becomes enormous when the drop sizes approach the molecular size. In the limit of how to fix hardwood floor finish single molecule the concept becomes meaningless.

When an object is placed on a liquid, its weight F w depresses the surface, and if surface tension and downward force becomes equal than is balanced by the surface tension forces on either side F swhich are each parallel to the water's surface at the points where it contacts the object.

Notice that small movement in the body may cause the object to sink. As the angle of contact decreases, surface tension decreases. The horizontal components of the two F s arrows point in opposite directions, so they cancel each other, but the vertical components point in the same direction and therefore add up [4] to how to start my own podcast on itunes F w.

The object's surface must not be wettable for this to happen, and its weight must be low enough for the surface tension to support it. If m denotes the mass of the needle and g acceleration due to gravity, we have.

To find the shape of the minimal surface bounded by some arbitrary shaped frame using strictly mathematical means can be a daunting task.

Yet by fashioning the frame out of wire and dipping it in soap-solution, a locally minimal surface will appear in the resulting soap-film within seconds.

The reason for this is that the pressure difference across a fluid interface is proportional to the mean curvatureas seen in the YoungLaplace equation. For an open soap film, the pressure difference is zero, hence the mean curvature is zero, and minimal surfaces have the property of zero mean curvature.

The surface of any liquid is an interface between that liquid and some other medium. Surface tension, then, is not a property of the liquid alone, but a property of the liquid's interface with another medium. The surface tension between the liquid and air is usually different greater than its surface tension with the walls of a container.

And where the two surfaces meet, their geometry must be such that all forces balance. Note that the angle is measured through the liquidas shown in the diagrams above. What are the main holidays in china diagram to the right shows two examples.

Tension forces are shown for the liquidair interface, the liquidsolid interface, and the solidair interface. In the diagram, both the vertical and horizontal forces must cancel exactly at the contact point, known as equilibrium. The horizontal component of f la is canceled by the adhesive force, f A. The more telling balance of forces, though, is in the vertical direction.

Since the forces are in direct proportion to their respective surface tensions, we also have: [10]. This same relationship exists in the diagram on the right. Water with specially prepared Teflon approaches this.

Because surface tension manifests itself in various effects, it offers a number of paths to its measurement. Which method is optimal depends upon the nature of the liquid being measured, the conditions under which its tension is to be measured, and the stability of its surface when it is deformed. An instrument that measures surface tension is called tensiometer. An old style mercury barometer consists of a vertical glass tube about 1 cm in diameter partially filled with mercury, and with a vacuum called Torricelli 's vacuum in the unfilled volume see diagram to the right.

Notice that the mercury level at the center of the tube is higher than at the edges, making the upper surface of the mercury dome-shaped. The center of mass of the entire column of mercury would be slightly lower if the top surface of the mercury were flat over the entire cross-section of the tube. But the dome-shaped top gives slightly less surface area to the entire mass of mercury. Again the two effects combine to minimize the total potential energy. Such a surface shape is known as a convex meniscus.

We consider the surface area of the entire mass of mercury, including the part of the surface that is in contact with the glass, because mercury does not adhere to glass at all. So the surface tension of the mercury acts over its entire surface area, including where it is in contact with the glass. If instead of glass, the tube was made out of copper, the situation would be very different. Mercury aggressively adheres to copper. So in a copper tube, the level of mercury at the center of the tube will be lower than at the edges that is, it would be a concave meniscus.

In a situation where the liquid adheres to the walls of its container, we consider the part of the fluid's surface area that is in contact with the container to have negative surface tension. The fluid then works to maximize the contact surface area. So in this case increasing the area in contact with the container decreases rather than increases the potential energy. That decrease is enough to compensate for the how to open a book store potential energy associated with lifting the fluid near the walls of the container.

If a tube is sufficiently narrow and the liquid adhesion to its walls is sufficiently strong, surface tension can draw liquid up the tube in a phenomenon known as capillary action. The height to which the column is lifted is given by Jurin's law : [9].

Pouring mercury onto a horizontal flat sheet of glass results in a puddle that has a perceptible thickness.

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Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Surface tension is what allows heavier than water i.e., denser than water objects such as razor blades, insects (e.g. water striders), to float and slide on a water surface without becoming even partly submerged. At liquidair interfaces, surface tension results from the greater attraction of. Oct 25, Nevertheless, any event that causes trauma can indeed result in PTSD, and abortion is no exception. A woman can be of sound and solid mind when she makes a choice to terminate a pregnancy, but it. Mar 22, When the ego satisfies the id by choosing a certain path to reach an individual's goals that the moral compass of the superego conflicts with, it can then regulate this behavior (and future choices) with causing a sense of guilt in the person. This is what is .

Follow CompassforSbc. Qualitative research is a key step in order to create program materials, tools and approaches that are culturally appropriate given the local context. Qualitative methods collect data and answers questions such as why and how and, although it provides rich detail, it is not meant to generalize to an entire population or intended audience.

Qualitative research is used to gain insight into the health issue or behavior the project intends to address; relevant characteristics of primary and secondary audiences; communication access, habits and preferences; and the main factors that hinder and drive behavior. Qualitative methods may be used when program planners need to get an understanding of the attitudes, habits and behaviors of their audience but do not need to estimate the proportion of the attitudes, beliefs or knowledge levels in the population.

It is critical to conduct qualitative research before implementing any SBCC program because without it you cannot know your intended audience, their current level of knowledge, their beliefs and attitudes, the channels through which they receive and act on information and the barriers to adopting new health behaviors. Any program development must begin with the audience and not be designed in isolation, removed from the intended audience.

Qualitative research should be developed by the research staff in close collaboration with program staff and any government or NGO counterparts who are designing the program and have clear knowledge of the program goals and objective.

Once designed, using qualitative methods requires certain skills in interviewing or conducting group discussions and an understanding of what the program needs to know about its audience in order to design appropriate strategies and materials to achieve the intended results. Qualitative research is conducted at the beginning of SBCC programs and can help researchers and program managers discover and explore themes or processes, provide personal narratives and uncover attitudes or ideas that are common among members of a population.

However, this method cannot be used to determine the proportion or number of people in an intended audience who think or act in a particular way. When starting to plan for qualitative formative research it is necessary to answer these key questions:. What is already known about the issue and the audience?

For example, what is already known about the factors that drive or hinder behavior among members of the intended audience regarding the health issue being addressed? How will the information gathered from this group discussion or interview be used to define a strategy, to create materials, to set priorities, etc.? What information is needed from participants that can inform decisions related to the design or implementation of an intervention? Formative research can have more than one objective, but each must be a clear statement about what you want to learn from the research.

Use active words to state your objectives, that is, what you want the research to achieve, for example:. Some topics may be important only to a specific group of people. For example, a study on breastfeeding practices will not be relevant to women who have never breastfed. Family planning, on the other hand, is an issue of some relevance to both married men and women but not to unmarried men and women. In the breastfeeding example women who are currently breastfeeding might have different attitudes, knowledge, and practices than women who breastfed years ago.

If both subgroups of women are part of the intended audience, then more discussion groups or interviews may be needed to understand the differences between them. Identifying the right respondents is key to gaining insights and information that are relevant to your planned intervention. The number of FGDs or IDIs that need to be conducted depends on a number of factors including the sameness homogeneity of the participants and saturation of the responses to more completely understand the issues.

If the target group is urban poor women, ages , then the FGDs or IDIs should consist of people who fit those criteria. Remember to think through different demographic factors that can affect the behaviors you are trying to influence and form the number of groups or interviews accordingly.

When putting together FGDs, it is important to consider the size of the groups. On average, people participate in each FGD because fewer than six participants produce less than a critical mass of discussion and interaction; groups larger than people can be hard to manage and it can be difficult to give everyone a chance to voice their opinions.

Begin by drafting a list of questions that match the research objectives. Once the questions have been drafted, review the purpose and objectives of your study. Narrow the list of questions to the ones that are most relevant and important for the research, ideally 7 to 10 questions, keeping in mind that each question will be followed by additional probing questions. You may list some probing questions to keep at hand and use depending on the direction that the discussion or interview takes.

The probing questions go deeper into understanding the underlying causes of the issue or behavior being discussed. Do not overload the discussion guide with too many questions. A FGD will generally last for 1 to 2 hours and an in-depth interview is usually shorter. Remember that the goal of qualitative research is to go deep into a few key ideas, not to cover a lot of topics superficially.

Questions should be open-ended i. Ensure that the questions are not biased and do not have language that might encourage participants to answer in a specific manner. Once the questions have been refined, arrange them in order so that they begin from the more general to the specific and in a way that will be comfortable for the participants.

The first one or two questions should be simple introductory or warm-up questions that put the respondents at ease, help establish rapport between them and the interviewer, and lead into the more serious questions. Effective FGD facilitation requires a special set of skills that not all facilitators have.

In an FGD, the facilitator must ensure that all participants share their opinions and interact with each other. An additional person who can take notes on the discussion is also important so the facilitator is free to moderate the discussion. Effective interviewing requires its own set of skills in creating personal rapport and trust that will enable the participant to honestly share his or her opinions and feelings.

Both facilitators and interviewers should be able to diplomatically keep the discussion on track and ensure that every participant is heard. They must be open-minded, flexible, patient, observant and good listeners and ensure that they do not lead or influence the conversation.

They need to be able to capture and build on trends in the conversation and use active and reflective listening. They should also be deeply familiar with the study topic and the larger project objectives so that he or she can help keep the conversation centered on the purpose and needs of the study. Facilitators or interviewers may be staff members, volunteers or third-party professionals, but in any case must have strong interpersonal communication skills, even though their interaction with the participants relies heavily on a script.

The questions created in Step 5 will be part of, but not all of, the script. The script should be structured as follows:. There are a number of factors to be taken into consideration when choosing the meeting place to ensure that you get the maximum input from the respondents who should be relaxed and open to share their thoughts and opinions.

Local leaders and people will help in determining the right place for this. Ideal locations are places that are:. Once the FGD or IDI is over the facilitator or interviewer should immediately write down any impressions or observations made during the discussion or interview that might help the analysis. The audiotape of the discussions should be carefully transcribed and, if needed, translated.

The facilitator is not required to do this, but if a third party provides that service, the facilitator should verify the accuracy of the transcriptions before they are subjected to analysis. Once the FGDs or IDIs are transcribed, they should be analyzed and coded for common themes related to the purpose and objectives of the study.

Arranging or grouping the statements by theme allows for better organization of data when pulling out results and key findings.

This qualitative formative research process and the resulting report will allow partners and key stakeholders to gain a better understanding of the target population, especially with regards to the health topic of interest. Print PDF. SBC How-to Guides are short guides that provide step-by-step instructions on how to perform core social and behavior change tasks. From formative research through monitoring and evaluation, these guides cover each step of the SBC process, offer useful hints, and include important resources and references.

The information provided on this website is not official U. Skip to main content. Search form Search. How-to Guide. Introduction What is Qualitative Research?

Why conduct Qualitative Research? Who should Conduct Qualitative Research? When should Qualitative Research be Conducted? Two of the most common approaches used in formative research are focus group discussions FGDs and in-depth interviews IDIs. These methods are effective for gaining insight into what motivates individuals and communities to behave a certain way and how they view the world or the community around them.

Both focus group discussions and in-depth interviews can reveal vital information that can help shape future quantitative research or they can be used to dig deeper or reveal additional insight into existing quantitative data, such as survey results.

Researchers will often opt for a combination of FGDs and IDIs in an effort to comprehensively study the population and their beliefs, attitudes and behaviors. The steps below can be applied to the development of both methods for conducting formative research. Steps Step 1: Identify needs. Step 2: Define objectives. Drop or rewrite any that are not Specific, Relevant and Feasible.

Step 3: Recruit the respondents. Step 4: Determine the number of focus groups or in-depth discussions. If the sample of participants is more heterogeneous i. If the sample is more homogenous similar attitudes or demographics with regard to the health issue , fewer FGDs or IDIs will be necessary since a more homogenous population often produces a smaller range of views and opinions.

Saturation refers to the point in the research process when all the viewpoints and information about the issue have been voiced already by participants. Saturation occurs when the last or final IDIs or FGDs do not reveal any new insights or ideas that were not mentioned in previous interviews or discussions.

Unless the research must explore the views of many different subgroups, most formative research studies conduct no more than 10 FGDs or IDIs before saturation is achieved. At that point, if the discussions and interviews are still producing new insights, then more sessions may be necessary.

Step 5: Create the questions. Step 7: Develop a script. Step 8: Choose a Place. Step Transcribe the Interviews. Step Analyze the Information. Gittelsohn, J. Lehigh University.

Conducting a Focus Group. Oak Ridge Institute for Science and Education. Overseas Development Institute. Pathfinder International.

5 thoughts on “What causes a compass to behave as it does

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