Answer:
The current at time t = 4.00 s is 0.766 A.
Step-by-step explanation:
Given that,
The quantity of charge through a conductor is modeled as :
![Q=(3t^4-2t+9)\ mC](https://img.qammunity.org/2021/formulas/physics/college/7nt7m97rfx9tk1cuqfiurqgjis8vtq86da.png)
We need to find the current (in A) at time t = 4.00 s. We know that the rate of change of electric charge is called electric current. It is given by :
![I=(dQ)/(dt)\\\\I=(d(3t^4-2t+9))/(dt)\\\\I=12t^3-2](https://img.qammunity.org/2021/formulas/physics/college/6k3lsd3o7k7quj4pws1iqbogosb9lkgnjn.png)
At t = 4 s
![I=12(4)^3-2=766\ mC/s\\\\I=0.766\ C/s=0.766\ A](https://img.qammunity.org/2021/formulas/physics/college/x5omokb0iwmtxvkjratcjbwfa0uhd23s57.png)
So, the current at time t = 4.00 s is 0.766 A. Hence, this is the required solution.