Finding charge, voltage and resistance

[Kathi201]

A heart defibrillato passes a 12A current through a patient's torso for 3E-3 seconds to restore it to normal beating.
a. How much charge passed through the patient's body?
b. What voltage was used if a total energy of 300J was dissipated? by the current
c. What was the resistance of the path through the person?

For a I know that the current is I and I have the time and I need to figure out Q but I do not have any equations that have all three of those variables in it so I am stuck on what equation to even start with.

For b I am struggling with the same problem. I know that Voltage is equal to the current x resistance but I do not know where the energy comes into place

I know the resistance is the resistivity/A is A the area? How would I figure that out then?


Any help would be appreciated!

 

[alphysicist]

Hi Kathi201,

A heart defibrillato passes a 12A current through a patient's torso for 3E-3 seconds to restore it to normal beating.
a. How much charge passed through the patient's body?
b. What voltage was used if a total energy of 300J was dissipated? by the current
c. What was the resistance of the path through the person?

For a I know that the current is I and I have the time and I need to figure out Q but I do not have any equations that have all three of those variables in it so I am stuck on what equation to even start with.

What is the definition of current?

For b I am struggling with the same problem. I know that Voltage is equal to the current x resistance but I do not know where the energy comes into place

What quantity can you find from knowing the energy and the time? How is that related to voltage?

I know the resistance is the resistivity/A is A the area? How would I figure that out then?

Once you find the voltage in part b, what is the relationship between voltage and resistance?

 

[baba89]

a. To find the charge that passed through the patient's body, we can use the equation Q = I x t, where Q is the charge, I is the current, and t is the time. In this case, we have I = 12A and t = 3E-3 seconds, so the charge passing through the patient's body is Q = (12A)(3E-3 seconds) = 0.036C.

b. To find the voltage used, we can use the equation E = V x I x t, where E is the energy, V is the voltage, I is the current, and t is the time. In this case, we have E = 300J, I = 12A, and t = 3E-3 seconds. Since we want to find the voltage, we can rearrange the equation to V = E/(I x t). Plugging in the values, we get V = (300J)/((12A)(3E-3 seconds)) = 25000V. So, the voltage used was 25000V.

c. To find the resistance of the path through the person, we can use the equation R = ρ x L/A, where R is the resistance, ρ is the resistivity, L is the length of the path, and A is the cross-sectional area. In this case, we have ρ = unknown, L = unknown, and A = unknown. Without knowing the specific values for these variables, we cannot calculate the resistance. However, we can estimate the resistance by using the voltage and current values we found in parts a and b. Using Ohm's law (V = I x R), we can rearrange the equation to R = V/I. Plugging in the values, we get R = (25000V)/(12A) = 2083.33Ω. So, the resistance of the path through the person is approximately 2083Ω.