A heater is to be designed using nichrome wire and is to use 5amperes of current

Question

A heater is to be designed using nichrome wire and is to use 5amperes of current when powered with 120 VAC. a. What resistance is needed if the wire will be at roomtemperature initially? b. What will the resistance increase or decrease to ifthe temperature of the wire increases to 1600? A heater is to be designed using nichrome wire and is to use 5amperes of current when powered with 120 VAC. a. What resistance is needed if the wire will be at roomtemperature initially? b. What will the resistance increase or decrease to ifthe temperature of the wire increases to 1600?

Explanation / Answer

   R = V / I
   = 120 / 5
   = 24
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  The resistance of the wire when the temperature isincreases to 1600 is
   R1600 = R [1 + alpha * change in temp. ]
Here alpha is temperature coefficient of resistance (approx. 0.0004 )
      = 24 [ 1 + (0.0004)(1600) ]
      = 39.36
The increase in resistance is
   = 39.36 -24
   =15.36

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