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

$\rho= R*\frac{A}{L}$

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

$R= \frac{V}{I}$

$R= \frac{120V}{9.85A}$

$R= 12.18\Omega$

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

$\rho= R*\frac{A}{L}$

$L=\frac{R\pi r^2}{\rho}$

$L = \frac{(12.18)(3.70*10^{-3})^2(\pi)}{1.5*10^{-6}}$

$L=349.34m$