Because the wood chips tend to settle, it is best to allow as little time as possible to elapse between when you shake the tank and when you energize the electrodes after you have set the tank on them. The photographs below show the electric field patterns that you obtain with the various electrode sets. Clicking on each image opens a larger-size photograph. An explanation of the physics follows the photographs.
Demonstrations The presence of such a force on an electrically charged object indicates the presence of an electric field. For example, if we take a charged rod and bring it near a second, similarly charged rod, it experiences a force due to the electric field set up by the second rod.
The shape of this field, that is, what its magnitude is at various points in the space around a charged object, depends on the shape of the object, the amount of charge on it, and the shapes of, and charges on, any other objects nearby. To help visualize electric and magnetic fields, Michael Faraday introduced the concept of lines of force. These are imaginary lines, which we draw such that the tangent of one at any point gives the direction of E there, and their density — the number of lines passing through unit cross-sectional area perpendicular to the lines — gives the magnitude of E.
The greater the density of lines, the greater the magnitude of E , and the fewer lines per unit area, the smaller the magnitude of E. For 14 Resources. We all use electrical devices in our lives, but many misconceptions exist about how these circuits actually work. In these CPD Magnetic fields will have to be shown; iron filings are a standard way to do this, but you may also find a magnaprobe useful — Teaching Guidance This episode introduces fields, field lines and equipotentials in the context of electric fields.
Much of this is revision The electric field line patterns for other charge configurations are shown in the diagrams below. In each of the above diagrams, the individual source charges in the configuration possess the same amount of charge. Having an identical quantity of charge, each source charge has an equal ability to alter the space surrounding it.
Subsequently, the pattern is symmetrical in nature and the number of lines emanating from a source charge or extending towards a source charge is the same. This reinforces a principle discussed earlier that stated that the density of lines surrounding any given source charge is proportional to the quantity of charge on that source charge.
If the quantity of charge on a source charge is not identical, the pattern will take on an asymmetric nature, as one of the source charges will have a greater ability to alter the electrical nature of the surrounding space. This is depicted in the electric field line patterns below. After plotting the electric field line patterns for a variety of charge configurations, the general patterns for other configurations can be predicted.
There are a number of principles that will assist in such predictions. These principles are described or re-described in the list below. It has been emphasized in Lesson 4 that the concept of an electric field arose as scientists attempted to explain the action-at-a-distance that occurs between charged objects.
The concept of the electric field was first introduced by 19th century physicist Michael Faraday. It was Faraday's perception that the pattern of lines characterizing the electric field represents an invisible reality.
Rather than thinking in terms of one charge affecting another charge, Faraday used the concept of a field to propose that a charged object or a massive object in the case of a gravitational field affects the space that surrounds it. As another object enters that space, it becomes affected by the field established in that space.
Viewed in this manner, a charge is seen to interact with an electric field as opposed to with another charge. To Faraday, the secret to understanding action-at-a-distance is to understand the power of charge-field-charge. A charged object sends its electric field into space, reaching from the "puller to the pullee. While the lines are invisible, the effect is ever so real. So as you practice the exercise of constructing electric field lines around charges or configuration of charges, you are doing more than simply drawing curvy lines.
Rather, you are describing the electrified web of space that will draw and repel other charges that enter it. Use your understanding to answer the following questions. When finished, click the button to view the answers.
Several electric field line patterns are shown in the diagrams below. Which of these patterns are incorrect? In D, the lines are not symmetrically positioned despite the fact that the object is a symmetrical sphere. Erin Agin drew the following electric field lines for a configuration of two charges. What did Erin do wrong? Consider the electric field lines shown in the diagram below.
Electric field lines are directed towards object A so object A must be negative. They are directed away from object B so object B must be positive. Consider the electric field lines drawn at the right for a configuration of two charges. Several locations are labeled on the diagram. Rank these locations in order of the electric field strength - from smallest to largest. Electric field strength is greatest where the lines are closest together and weakest where lines are furthest apart.
Use your understanding of electric field lines to identify the charges on the objects in the following configurations. Objects B, D and E are negatively charged. The principle is: electric field lines always approach negatively charged objects and are directed away from positively charged objects.
Observe the electric field lines below for various configurations.
0コメント