# How long should a current of 2.5A (amperes) flow through a conductor

How long should a current of 2.5A (amperes) flow through a conductor with a resistance of 18 ohms and so that 81kJ of energy would be released in it?

We translate the values ​​from given to the SI system:
Q = 81 kJ = 81000 J.
The energy released in the conductor when an electric current passes through it:
Q = P * τ
Formula for determining electrical power:
P = U * I
According to Ohm’s law, the amount of current is directly proportional to the applied voltage and inversely proportional to its resistance:
I = U / R
U = I * R
Substitute into the expression for the power:
P = U * I = I * R * I = I² * R
Substitute in the expression for the energy:
Q = P * τ = I² * R * τ =
Let us express time from this expression:
τ = Q / (I² * R)
Substitute the numerical values ​​and find the time:
τ = Q / (I² * R) = 81000 / (2.5² * 18) = 720 s.
Answer: 720 sec or 12 min is needed. One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.