Answer:
0.78 ohm and 3.8 A
Explanation:
We are given that
Length of carbon resistor,l=7mm=[tex]7\times 10^{-3} m[/tex]
1mm=[tex]10^{-3} m[/tex]
Cross section area=A=[tex]0.3mm^2=0.3\times 10^{-6} m^2[/tex]
Conductivity of carbon,[tex]\sigma=3\times 10^4/ohm [/tex]
Potential difference at one end,[tex]V_1=13 V[/tex]
Potential difference at other end,[tex]V_2=16 V[/tex]
We have to find the resistance and the current.
Potential difference,V=[tex]V_2-V_1=16-13=3 V[/tex]
[tex]\rho=\frac{1}{\sigma}=\frac{1}{3\times 10^4}=\frac{1}{3}\times 10^{-4} ohm m[/tex]
[tex]R=\frac{\rho l}{A}[/tex]
Using the formula
[tex]R=\frac{1}{3}\times 10^{-4}\times \frac{7\times 10^{-3}}{0.3\times 10^{-6}}[/tex]
[tex]R=0.78\Omega[/tex]
Current,I=[tex]\frac{V}{R}[/tex]
Using the formula
Current, I=[tex]\frac{3}{0.78}=3.8 A[/tex]
