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Ohms law hypothesuis
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Investigating the Relationship Between Temperature and Resistance in a Themistor
Aim
To investigate the relationship between temperature and resistance in a thermistor.
Introduction
A current is the flow of charge round a circuit, this can be in the form of ions in a liquid or electrons in a metal.
Resistance is anything that slows the flow of electrons round the circuit.
Ohm's law states that the voltage is equal to the current multiplied by the resistance - V=IR
This can be re-arranged to say R=V/I.
Ohms law states that in a metal component the ratio of voltage to current remain constant, meaning that the resistance stays the same as long as the temperature remains the
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I need to do this because although I am keeping the voltage the same on the power pack this may not be accurate due to the change in resistance round the circuit.
Plan
Apparatus-
Ammeter
Thermistor
Bunsen burner
Tripod
Clamp stand
Clamp
Gauze
Thermometer
Beaker
Water
Power pack
Wires
Crocodile clips
Voltmeter
I will set up the equipment as shown in the diagram.
I will fill the beaker with water of room temperature.
I will light the Bunsen burner and when the temperature reaches 250C will read the current through the thermistor and the voltage across it and record them.
I will do this at each 50C interval up to
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This is because as the thermistor increases in temperature the lattice atoms move faster and are colliding with the electrical current and slowing down the flow of charge. In a normal wire this would make the resistance decrease but because a thermistor is a semiconductor there is a second stronger effect which out weighs this. This effect means that the outer electrons are not free at room temperature but when heated the get more energy and are freed. This means that there are more electrons available to conduct. This does not apply in a normal wire because the outer electrons are free and the inner electrons are tightly held in the atom. The two competing effects in the thermistor mean that when the temperature is increased the resistance decreases. If the resistance decreases then the current increases.
The graph shows the resistance dropping from about 300 ohms to about 50 ohms.
This is a drop of 250 ohms. The temperature went from 250C to 1000C. By 500C the resistance has already dropped to about 50 ohms which
Then we will remove the cell and connect point A to point B, at the
For any electric circuit, which consists of various passive elements (i.e. resistors, capacitors and inductors) the behaviour of the whole circuit to an applied ac voltage, is dependent upon both the behaviour of individual elements, and also on their arrangement in the circuit with respect to each other. If a dc direct voltage is applied to the elements that comprise the equivalent circuit, the resulting current can be measured using Ohms law.
You can make an electric current in a wire if a wire is at right
I also decided to use a wooden block to keep hold of the wire, because
Neurons are not necessarily intrinsically great electrical conductors, however, they have evolved specialized mechanisms for propagating signals based on the flow of ions across their membranes. In their inactive state, neurons have a negative potential, called the resting membrane potential. Action potentials change the transmembrane potential from negative to positive. Action potentials are carried along axons, and are the basis for "information transportation" from one cell in the nervous system to another. Other types of electrical signals are possible, but we'll focus on action potentials.
In electroplating the flow of current is used to coat one metal with another such as copper with silver or gold. This is done when electric current is passes through a solution (electrolyte). When two electrodes are connected to a power supply in the form of a circuit, current or electricity is carried through the power supply, there is a splitting in the electrolyte and atoms from the metal that are in the solution are carried to the top of one of the electrodes. This is called electroplating and is used on many metals to prevent corrosion from occurring. Both of the materials must be conductors in order for current to be carried through. Electroplating is also known as
When introduced into an ionic solution, positively charged ions will be electrostatically attracted to the anode and the negatively charged ions will be electrostatically attracted to the cathode. This act of moving ions means that charges are able to move from anode to the cathode and complete the circuit. These moving ions are essentially the same as moving electrons (electricity). This process of putting electrodes into a solution, using a direct electric current (D.C.), and separating chemicals based on their charge is known as electrolysis
F Another wire, or exact same properties (Nickel Chrome, thickness 34). mm and length 30cm) was placed on top of the previous wire, in the same position, both straight and flat. F. The power was turned on again and the same procedure was repeated. recording current and voltage at three points on the variable. resistor.
The only problem with this experiment is that when the current passing through the battery circuit was at a continual rate there was...
1) ABSTRACT: Relative motion between a magnetic field and a conductor are needed to create a voltage within the conductor. For current to flow the conductor must be a complete loop, if not the current will not flow.
First off, what is current. Current is expressed in a unit called Amps. Amps are a measurement of how many electrons pass per second. That is to say, a wire with 40 coulombs passing any point in a 2 seconds would be said to have 20 Amps of current (40 Coulombs (a unit of charge given as 6.24x1018 electrons) / time in seconds or in this case, 2 seconds. The Amp is also known as Coulombs per second) Another trick about current is that it is measured in the movement of the positive charge. Literally that is to say the current moves in oppostion to the electrons. This is because originally it was thought that the positive charge is what moved, both are viable, but in reality a positive charge is generally fixed since within an atom the electrons are migratory, while the protons and neutrons tend to be stationary.
All useful generators of electricity come in two basic forms, alternating current and direct current. Direct current (dc) comes from generators that do not change in polarity, always producing a positive charge. In alternating current (ac) the polarity of the terminals is always changing from positive to negative. Thus you are left with alternating current flow. There are different ways of measuring and generating alternating and direct current.
When magnetic field is applied to a current carrying conductor in a direction perpendicular to that of the flow of current, a potential difference or transverse electric field is created across a conductor. The potential difference created across the conductor due to the applications of magnetic field in a direction perpendicular to that of the flow of current is called Hall Effect.
Again, it is the most common means of energy transfer and by understanding exactly what conduction means, we can identify it in some of the simple things we do. For instance, think of a pot placed on the stove, on a hot burner. The burner and the bottom of the pot are obviously touching, therefore the pot begins to heat up and get hot as well. As physical contact is the key element in heat transfer through conduction, we can see how important a role it plays in this situation. Now, say that your food is done, you turn the burner off and grab the handle of the pot, only to find that it is extremely hot as well. Again, we can thank conduction for this- as the heat was transferred through the bottom of the pot to the handle. Another example of conduction can be seen through ironing. We plug in and heat up the iron prior to placing it on the clothing in which we wish to smooth out. Once the iron has heated up, we place it on top of the article of clothing and it then heats up the clothing as well. Again, physical contact between the iron and the shirt show us that conduction plays the role of heat transfer in this scenario too. For a final example of heat transfer through conduction, let’s imagine a child, playing outside in the snow on a rather cold day. Once outside for a bit, he is freezing and decides to come inside. He takes off his snow gear, cuddles up to his father and begins to warm up
The phenomenon called electromagnetic induction was first noticed and investigated by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is a very important concept. Faraday discovered that, whenever the magnetic field about an electromagnet was made to grow and collapse by closing and opening the electric circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also investigated the possibility that a current could be produced by a magnetic field being placed near a coiled wire. Just placing the magnet near the wire could not produce a current. Faraday discovered that a current could be produced in this situation only if the magnet had some velocity. The magnet could be moved in either a positive or negative direction but had to be in motion to produce any current in the wire. The current in the coil is called an induced current, because the current is brought about (or “induced”) by a changing magnetic field (Cutnell and Johnson 705). The induced current is sustained by an emf. Since a source of emf is always needed to produce a current, the coil itself behaves as if it were a source of emf. The emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused a current to flow in the wire as long as it was moving as in the magnet and coiled wire set-up.