A resistor is constructed of a carbon rod that has a uniform cross-sectional area of 5.0 mm^2. When a potential difference of 15V is applied accross the ends of the rod there is a current of 4.0x10^-3 A in the rod. What's the rod's resistant and length?

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Answer 1 · 2018-02-13T14:40:34

The resistance is #=3.7510^3Omega# and the length is #=536m#

Apply the following equations :

#"Ohm's Law"#, #U=RI#

And

#R=rhoL/s#

The voltage is #U=15V#

The current is #I=4*10^-3A#

The resistance is

#R=U/I=15/(4*10^-3)=3.7510^3Omega#

The cross section is #s=5mm^2=5*10^6m^2#

The resistivity of carbon is #rho=3.5*10^-5Omegam#

The length of the rod is

#L=Rs/rho=3.75*10^3*(5*10^-6)/(3.5*10^-5)=5.36*10^2m#