# Ohm's Law: Help please and thank you

• Malaya
In summary, a cylindrical copper cable with a current of 1300 A and a potential difference of 1.6 10-2 V between two points 0.38 m apart has a radius of approximately 760333.43m. The calculation for finding the radius involved using the equations V=IR and R=rho*L/r^2pie. However, the incorrect step of 1.23E-5 ohms=1.7e-8*(0.38m/r^2pie) led to the incorrect final answer. The correct calculation is r^2= 1.7*10-8*(.38)/(π*1.23*10-5).

## Homework Statement

A cylindrical copper cable carries a current of 1300 A. There is a potential difference of 1.6 10-2 V between two points on the cable that are 0.38 m apart. What is the radius of the cable?

I=1300A
V=1.6e-2 V
l=0.38m
rho=1.7e-8(resistivity of copper)
r=?

## Homework Equations

V=IR
Where: V=voltage, I=Current, R=Resistance

R=rho* L/r^2pie
Where: R= resistance, rho=1.7e-8(resistivity of copper), Length in meters, r=radius

## The Attempt at a Solution

1. Find Resistance.
V=IR
1.6e-2V=1300A*R
R=1.23E-5 ohms

then I used:
R=rho* L/rpie^2
1.23E-5 ohms=1.7e-8*(0.38m/r^2pie)
2.09e-13=0.38m/r^2pie
6.57e-13=0.38m/r^2
6.57e-13*r^2=0.38m
5.78e11=r^2
r=760333.43m

what do I keep doing wrong??

Malaya said:
1.23E-5 ohms=1.7e-8*(0.38m/r^2pie)
2.09e-13=0.38m/r^2pie

That step is woefully wrong.

Perhaps if you rewrote it

r2= 1.7*10-8*(.38)/(π*1.23*10-5)

Based on your calculations, it seems like you are using the correct equations and correctly plugging in the given values. However, there may be a mistake in your algebra or in converting units. Remember to check your units and make sure they are consistent throughout the problem. Also, be careful with your use of pi - it should be squared in the equation for resistance. Another potential issue could be with the given values - double check to make sure they are accurate and in the correct units. If you are still having trouble, try breaking down the problem into smaller steps and double check each step to identify where the mistake may be occurring.

## What is Ohm's Law?

Ohm's Law is a fundamental law of electricity that states the relationship between voltage, current, and resistance in an electrical circuit. It states that the current through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

## Who discovered Ohm's Law?

Ohm's Law was discovered by German physicist Georg Simon Ohm in 1827. He published his findings in a paper titled "The Galvanic Circuit Investigated Mathematically" and it is now considered one of the most important laws in physics.

## What is the formula for Ohm's Law?

The formula for Ohm's Law is V = IR, where V is voltage, I is current, and R is resistance. This formula can also be rearranged to solve for any of the variables, such as I = V/R for current or R = V/I for resistance.

## How is Ohm's Law used in everyday life?

Ohm's Law is used in many everyday devices, such as light bulbs, to determine the appropriate voltage and resistance needed for the circuit to function properly. It is also used in household appliances, electronics, and power systems to ensure safe and efficient operation.

## What are some practical applications of Ohm's Law in the scientific field?

Ohm's Law is fundamental to understanding and analyzing electrical circuits and is used in various fields of science, such as physics, engineering, and electronics. It is also used in research and development of new technologies, such as renewable energy sources and electric vehicles.