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Earn 100

What is the use of a thermistor?

Important Questions on Electric Circuits

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A thermocouple produces a thermo-e.m.f. of 40μV/C. A thermopile is made by using 150 such thermocouples. The temperatures of the two junctions are 20°C and 40°C. How much thermo-emf will be generated in the thermopile?
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The resistance of a wire of iron is 10 Ω and temperature coefficient of resistivity is 5×10-3 °C-1. At 20°C, it carries 30 mA (milliamperes) of current. Keeping the potential difference between its ends constant, the temperature of the wire is raised to 120°C. The current (in mA) that flows in the wire at 120°C is nearly,
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This is a circuit

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State and explain how the reading on the ammeter changes when the temperature of the thermistor is increased.

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The graph in Figure was obtained by measuring the resistance R of a particular thermistor as its temperature e changed. Determine the temperature when its resistance is:2000Ω.

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A student connects a circuit with an NTC thermistor, a filament lamp and a battery in series. The lamp glows dimly. The student warms the thermistor with a hair dryer. What change will the student notice in the brightness of the lamp? Explain your answer

 

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The graph in Figure was obtained by measuring the resistance R of a particular thermistor as its temperature e changed Determine the temperature when its resistance is: 5000Ω.

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Thermistor has a resistance of_____ .
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A platinum resistance thermometer reads 0o when its resistance is 80 Ω and 100o when its resistance is 90 Ω. Find the temperature at the platinum scale at which the resistance is 86 Ω.
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The graph in Figure was obtained by measuring the resistance R of a particular thermistor as its temperature changed.

Determine its resistance at: 20°C

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A student connects a NTC thermistor to a battery and an ammeter. He places the thermistor in a beaker of water and gradually heats the water from 10 oc to its boiling point, recording the value of the current as he does so. He then plots a graph of the current in the thermistor against the temperature of the water Explain how the student could now use the thermistor as a thermometer. 

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The resistance of a metal wire changes with temperature. This means that a wire could be used to sense changes in temperature, in the same way that a thermistor is used 

 Suggest one advantage a thermistor has over a metal wire for this purpose.

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a) Draw the circuit symbol for a thermistor.

b) Give one use for a thermistor.

c) Explain why a thermistor is suitable for this use.

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This is a circuit.

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Which line in the table shows the changes to the lamp and the voltmeter reading when the temperature rises?

Lamp Voltmeter reading
gets brighter decreases
gets brighter increases
gets dimmer decreases
gets dimmer increases

 

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The resistance of a bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance is 0.005°C-1, its resistance will become 200 Ω at a temperature of,
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A student connects a thermistor to a battery and an ammeter. He places the thermistor in a beaker of water and gradually heats the water from 10°C to its boiling point, recording the value of the current as he does so. He then plots a graph of the current in the thermistor against the temperature of the water

(a) Sketch the graph you would expect the student to obtain from the experiment

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The graph in Figure was obtained by measuring the resistance R of a particular thermistor as its temperature e changed. Determine its resistance at: 45°C.

 

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Two resistances, R1 and R2 are made of different materials. The temperature coefficient of the material of R1 is α and of the material R2 is -β. The resistance of the series combination of R1 and R2 will not change with temperature if R1R2 equals,
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A resistance thermometer reads R=20.0  Ω27.5  Ω, and 50.0  Ω at the ice point 0oC, the steam point 100oC and the zinc point 420oC respectively. Assuming that the resistance varies with temperature as Rθ=R01+αθ+βθ 2, find the values of R0α and β. Here θ represents the temperature on Celsius scale.