The correct option is
A No change in the value of current passing through resistance
ALet us assign same electric potential to the points connected through same conducting wire in the given circuit.
Now redrawing the circuit, when switch
S is open.
Due to switch
S in open condition the resistance in that branch will vanish. Thus, there are effectively three resistances with value
r connected in parallel between points
1 and
2.
⇒Req=r3
The current supplied by battery in the circuit will be,
i1=E(r3)=3Er
Since all the three resistances are identical, therefore current will get distributed equally in each of them.
Hence current through resistor
A,
iA=i13=Er
After the switch
S is closed:
We can observe that there are effectively four resistances with value
r connected in parallel between points
1 and
2.
⇒Req=r4
The current supplied by battery in the circuit will be,
i2=E(r4)=4Er
Since all the four resistances are identical, therefore current will get distributed equally in each of them.
Hence current through resistor
A,
iA=i24=(4Er)4=Er
⇒The value of current through resistor
A will remain the same.
Why this question?
Tip––––:In such problems always focus on obtaining a simple circuit by using point potential technique.
The current will not flow in a branch in which the electrical path is broken, thus resistance in such paths can be neglected.
Caution:––––––––––In this question, the value of current through resistance A has not changed due to identical resistance. However the current in circuit will increase after switch S closed because Req↓ for the circuit. |