Question

A portion of Nichrome wire of radius3.70mm is to be used in winding a heating coil. If the coil must draw a current of9.85A when a voltage of 120 V is applied across its ends, find the following. (Take the resistivity of nichrome to be1.50A portion of Nichrome wire of radius3.70mm is to b10-6?? m.)(a) the required resistance of the coil(b) the length of wire you must use to wind the coil.

Answer 1

To develop this problem it is necessary to have the concepts related to Ohm's law and resistivity.

Ohm's law is defined by the equation

`V= RI`

Where

R=Resistence

I = current

V= Voltage

While the resistivity equation is given by

`\rho= R*(A)/(L)`

Where

`\rho=` resistivity

A= cross-section area

R= Resistance

L=Lenght of wire

A) We can find the resistence re-arranging our first equation, so

`R= (V)/(I)`

`R= (120V)/(9.85A)`

`R= 12.18\Omega`

B) From our second equation we can re-arrange for L, so

`\rho= R*(A)/(L)`

`L=(R\pi r^2)/(\rho)`

`L = ((12.18)(3.70*10^(-3))^2(\pi))/(1.5*10^(-6))`

`L=349.34m`