Three bulbs X, Y and Z are connected as shown in figure. The bulbs Y and Z are identical. If bulb Z gets fused, then

Options

A. Both X and Y will glow more brightly
B. Both X and Y will glow less brightly
C. X will glow less brightly and Y will glow more brightly
D. X will glow more brightly and Y will glow less brightyly

Answer

C

Explanation

If bulb Z is fused, the current stops flowing through Z. The effective resistance of the circuit due to bulbs X and Y in series becomes more as compared to before. Due to which, the current in the circuit decrease.
`therefore` brightness `prop(current)^(2)`

Total resistance of the circuit `=(2xx4)/(2+4)+0.8`
`(8)/(6)+0.8=(12.8)/(6)Omega`
Main current in the circuit`=(14)/(12.8//6)=(84)/(12.8)A`
Reading of ammeter `(84)/(12.8)xx(2)/(6)=2.18A`
So, the brightness of bulb X decreases, Now, bulb Y gets more current than before fusing the bulb, Z.
`therefore` Brightness of bulb Y will increase.