For example, a battery may have a no-load voltage of 13 VDC that drops to 12 VDC when a load is applied. It will have a certain "no-load" voltage that usually drops when a load is applied. The same thing happens to sources of electrical energy. As you started to climb a hill you will experience an increased load and start to slow down. Suppose you are riding a bicycle on a level road. This is often called voltage.įorgive me as I add an analogy that would appear not to belong. We would say the the meter is measuring the potential difference between the two points. It could be a battery, solar cell, or coil of wire as shown in this video. It does not matter what is being measured. The total flux through all six faces should be given by the above equation, so a sixth of that should yield the flux through one square, no Doing this yields. The red probe goes to one part of the circuit and the black probe goes to another. Suppose I then let the Gaussian surface be a cube of side length 40cm centered around and enclosing the charge. If you have a voltmeter in had you could measure voltage as the difference between any two point in a circuit. Here is an answer from an electrical engineer's perspective - it may not line up with a physicists answer. The compass needle will line up along the direction of the magnetic field produced by the magnet, as depicted in. This can be readily demonstrated by moving a compass near the magnet. In a similar manner, a bar magnet is a source of a magnetic field B G. So induced current always flows in a direction that oppose the motion of the magnet.This is Lenz's law. We have seen that a charged object produces an electric field E G at all points in space. This is not possible (law of conservation of energy). If in case the induced current promotes the motion of the magnet, it stars moving at a faster rate and the electric energy(induced) and kinetic energy(of the magnet) starts increasing, without any work done. The work done in moving the magnet towards the coil is converted into electrical energy, which gets dissipated into heat energy.The current flows in a direction to oppose the motion of the magnet. The direction of the induced current is found from Lenz' law as follows. Now we know that as the magnet moves through the coil magnetic flux linked with the coil changes inducing a current. If the magnet is withdrawn from the coil upper end acquires south polarity, so work is done against the force of attraction. Upper end of the coil acquires north polarity, hence work is done against the force of repulsion to move the magnet. Using cylindrical coordinates, we can assert that in case of cylindrical symmetry, the magnitude of electric field at a point will a function on s s only. Consider that the magnet's north pole moves towards the coil. If the electric field is uniform, the electric flux passing through a surface of vector area S is What is the flux of the electric field through the surface Solution: The surface that is defined corresponds to a rectangle in the (xz) plane with area (ALH). For simplicity in calculations, it is often convenient to consider a surface perpendicular to the flux lines. Electric flux is proportional to the total number of electric field lines going through a surface. The density of these lines corresponds to the electric field strength, which could also be called the electric flux density: the number of "lines" per unit area. Note that field lines are a graphic illustration of field strength and direction and have no physical meaning. In pictorial form, this electric field is shown as a dot, the charge, radiating "lines of flux". It represents completely covering the surface with a large number of tiny patches having areas d A. The electric field is the gradient of the potential.Īn electric charge, such as a single electron in space, has an electric field surrounding it. We have so far established that the total flux of electric field out of a closed surface is just the total enclosed charge multiplied by 1 / 0, E d A q / 0. The electric field E can exert a force on an electric charge at any point in space. In electromagnetism, electric flux is the measure of the electric field through a given surface, although an electric field in itself cannot flow.
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