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What do you call a variable resistor that is set up to alter the size of the current in a circuit?
Wiki User
∙ 13y ago
A thermister is a device that changes resistance depending on temperature. A photo resistor changes resistance based on light. Both of these could be used with an amplifying circuit to vary current flow.
Wiki User
∙ 13y ago
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What do you call the variable resistor when it is set up to alter the size of the voltage over the resistor?
A potentiometer.
If the resistance in the circuit is increased what will happen to the current and voltage?
* resistance increases voltage. Adding more resistance to a circuit will alter the circuit pathway(s) and that change will force a change in voltage, current or both. Adding resistance will affect circuit voltage and current differently depending on whether that resistance is added in series or parallel. (In the question asked, it was not specified.) For a series circuit with one or more resistors, adding resistance in series will reduce total current and will reduce the voltage drop across each existing resistor. (Less current through a resistor means less voltage drop across it.) Total voltage in the circuit will remain the same. (The rule being that the total applied voltage is said to be dropped or felt across the circuit as a whole.) And the sum of the voltage drops in a series circuit is equal to the applied voltage, of course. If resistance is added in parallel to a circuit with one existing circuit resistor, total current in the circuit will increase, and the voltage across the added resistor will be the same as it for the one existing resistor and will be equal to the applied voltage. (The rule being that if only one resistor is in a circuit, hooking another resistor in parallel will have no effect on the voltage drop across or current flow through that single original resistor.) Hooking another resistor across one resistor in a series circuit that has two or more existing resistors will result in an increase in total current in the circuit, an increase in the voltage drop across the other resistors in the circuit, and a decrease in the voltage drop across the resistor across which the newly added resistor has been connected. The newly added resistor will, of course, have the same voltage drop as the resistor across which it is connected.
Is the heat loss and current of a resistor affected by being in a parallel circuit or can you just calculate it the same as in series?
The heat generated by any particular resistor depends (at least electrically) solely on the power it dissipates. Power dissipation in a resistor is equal to current squared times resistance, and the current through the resistor is equal to the voltage across it divided by the resistance. If we take a 10 ohm resistor ('your resistor') and put it in a series circuit such that there is 10 volts across your resistor, the current through it will be 1 ampere (10/10=1). the power dissipated will be 10 watts (1^2 * 10=10). If we put your resistor in a parallel circuit that also puts 10 volts across it, then the current and power will be the same. Your resistor does not know or care where the voltage came from. From this point of view, once you get down to the voltage across the resistor, it does not matter what type of circuit it is in. On the other hand, for any given power supply voltage, then the type of circuit and the value of external components certainly does affect the terminal voltage and thus the current through as well as the power dissipated by the resistor. In a parallel circuit, the voltage across your resistor remains basically the same no matter what resistance you put in parallel with it (unless you overload the power supply or the power supply has high internal resistance). In this case, the voltage across the resistor is the same as the power supply, current is I=E/R, R being that resistor only, and power is P=I^2 * R. In a series circuit the current through the resistors is I=E/R, R being the total resistance (including the other resistor(s)). The power dissipation in your resistor will then be P=I^2 * R, I being the series current we just calculated, and R being your resistor only. Since the other resistors affect the current, and since the current is the same no matter where you measure in a series circuit, then the voltage across your resistor and thus the power dissipation will be affected. The voltage across your resistor will be E=I*R, I being the series current we just calculated, and R being your resistor only. So, while the calculation for power dissipated in a particular resistor does not change relative to what type of circuit it is in, the calculation to arrive at the voltage across the resistor and/or the current through it (which you will then need to calculate power) does. Keep in mind there are other mechanical parameters that influence the actual case temperature of the resistor. Physical size of the case, composition, and airflow velocity, if any, will alter the case-to-ambient thermal conductivity. Ambient temperature will also be a factor in the final temperature.
What is the purpose of a variable resistor?
A variable resistor is used in cicuits to vary the magnitude of resistance passing through the resistor. It is commonly used to change the value of current across a circuit to find relationships of current and voltage.
How does a 120v residential dimmer switch work?
Just to dim lights, it could be just a simpler variable resistor or rheostat. This just lowers the voltage and dims the lights. Makes the bulbs last longer, but way reduces their effientcy (sp?) This doesn't work with AC motors though, lowering their voltage will burn 'em up. What you need for these is a Variac. It keeps the voltage constant, but limits the current. This type of circuit is called RC (resistor-capacitor) and uses a variable coil to alter the speed. Like on a ceiling fan or Honda generator that uses a feedback loop dependant upon load. Hope that helps.
Why a voltage is always connected in parallel?
Because Voltmeter measures potential difference BETWEEN two points so it should be connected to these two points and the only way for circuit and voltmeter to be both connected to the same 2 points is in parallel. Ampermeters measure the current THROUGH some circuit so the same current that is flowing through this circuit should flow through the ampermeter too. The only way is to let the current going through the circuit to go through the ampermeter later or before, so you have to connect ampermeter in series with your circuit. The fact that voltmeters have high resistance while ampermeters have low resistance is the side effect of the way how they are connected to reduce the error introduced by devices into measured value.
Can a magnetic field affect the performance of electrical circuits?
You better believe it can, but only if it's changing, otherwise the magnetic field can just pull or push the electrons in the circuit towards or away from it, but it can't slow them down. If the magnetic field is changing, a phenomenon called inductance happens. Inductance is an applied current to a circuit by a changing magnetic field. As you might imagine, an additional applied current to a circuit can definitely change the circuit's behavior and alter its performance.
What is the difference between a manipulated verible and a responding variable?
A manipulative variable is the variable you can alter, while the responding variable is the variable you have no control over. A manipulated variable is what is changed purposely throughout the experiment. The responding variable is which you have to measure to get your results I think. But the responding variable depends on the dependent variable. I believe I'm right!
Why is voltmeter connected in parallel and ammeter connected in series in a circuit?
An ideal voltmeter has infinite impedance(resistance). If you were to break the circuit and put it in series and try to make a measurement, it is easy to see that the circuit would act completely differently and your measurement would be wrong. An ideal ammeter is always connected in series because it has 0 resistance, so all of the current would flow through it, and not through the wire that you are trying to measure the current of.A better answer though is to think about what you are trying to measure. When you say something is 3 Volts, that is a difference between the voltages at two different points. If you want to see what the voltage drop across a resistor is, for example, you need to put one probe of the voltmeter on one side of the resistor and the other probe on the other side of the resistor. That setup is simply called being in parallel.Voltage is potential difference between two points, hence measured across or in parallel, where as current is measured in series since current flows (*)
Write down a PHP code to add a session variable?
The preferred way is to simply alter the session superglobal. <?php $_SESSION['variable'] = "value"; ?>
What causes an alternating current in a generator?
The spinning magnet in generators.
What is idenpendent variable in a science project?
The dependent variable is the object(s) being tested in the experiment. So if you were to pop a balloon, then the BALLOON would be the dependent variable. Why? Because it is the object being tested. Hope this helped. -6th grader.
