Question

A source of e.m.f. E= 15 v and having negligible internal resistance is connected to a variable resistance so that the current in the circuit increase with time as I = 1.2t + 3. Then total charge will flow in first seconds will be:

• A. 10C
• B. 20C
• C. 30C
• D. 40C

Answer 1

The correct option is C 30C

We knwo that $i=\frac{dQ}{dt}$

According to question:

$\Rightarrow dQ=idt\Rightarrow Q={\int }_{r_1}^{r_2}idt={\int }_0^5(1.2t+3)dt$

$={[\frac{1.2t^2}{2}+3t]}_0^5=30C$