1) The magnetic flux in a closed circuit of resistance 10 Ω varies with time as $\phi=(2t-4t^{2}+1)$ . the current in the loop will change its direction after a time of A) 0.25 sec B) 0.5 sec C) 1 sec D) none Answer: Option AExplanation:$e=-\frac{d\phi}{dt}=[-2+8t+0]$ $\Rightarrow 8t=2\Rightarrow t=\frac{1}{4}sec=0.25 sec$
