Current Electricity Ques 29
- When the switch $S$ in the circuit shown is closed, then the value of current $i$ will be
(2019 Main, 9 Jan I)
(a) $4$ $ A$
(b) $3 $ $A$
(c) $2$ $ A$
(d) $5$ $ A$
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Answer:
Correct Answer: 29.(d)
Solution:
- When the switch ’ $S$ ’ is closed the circuit, hence formed is given in the figure below,
Then, according to Kirchhoff’s current law, which states that the sum of all the currents directed towards a point in a circuit is equal to the sum of all the currents directed away from that point.
Since, in the above circuit, that point is ’ $C$ '
$\therefore i _1+i _2=i $
$\Rightarrow \frac{V _A-V _C}{2}+\frac{V _B-V _C}{4}=\frac{V _C-V}{2} $
$\text { or } \quad \frac{20-V _C}{2}+\frac{10-V _C}{4}=\frac{V _C-0}{2} $
$\Rightarrow 20-V _C+\left(10-V _C\right) 2=V _C $
$ 40=V _C+3 V _C $
$\text { or } \quad 40=4 V _C $
$\therefore \text { The current, } i=\frac{V _C}{2}=\frac{10}{2}=5$ $ A$
BETA
