The amount of the charge passed in time t through a cross-section of a wire is $Q_t=At^2+Bt+C.$ If the value of A, B, C in SI units respectively are 5 ,3, 1, the value of current at t = 5 s is

66 A 70 A 53 A 65 A

53 A

The correct answer is option (3) : 53 A $Q=At^2+Bt+C$ and $A=5, B=3, C=1$ $⇒Q_t=5t^2+3t+1, i=\frac{dQ}{dt}$ $⇒i=10t+3;[i]_{t=5}=10\times 5 + 3= 53\, A$