Subject :NSO Class : Class 7
Three similar light bulbs are connected to a constant voltage d.c supply as shown in the diagram. Each
bulb operates at normal brightness and the ammeter
(of negligible resistance) registers a steady current.
The filament of one of the bulbs breaks. What happens
to the ammeter reading and to the brightness of the
remaining bulbs?
| Ammeter reading | Bulb brightness | |
| A | Increase | Increase |
| B | Unchanged | Unchanged |
| C | Decrease | Unchanged |
| D | Decreases | Decreases |
The correct answer should be D because when current decreases,brightness also decreases
Ans 1:
Class : Class 7
Ans 2:
Class : Class 4
how come??
Ans 3:
Class : Class 9
Since it is in a parallel circuit, resistance offered is more after one of the bulbs is fused. This will increase the brightness of the bulb but decrease the ammeter reading since current is inversely proportional to resistance