Question 18N.2.SL.TZ0.c
| Date | November 2018 | Marks available | [Maximum mark: 1] | Reference code | 18N.2.SL.TZ0.c |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Outline | Question number | c | Adapted from | N/A |
A lighting system consists of two long metal rods with a potential difference maintained between them. Identical lamps can be connected between the rods as required.
The following data are available for the lamps when at their working temperature.
Lamp specifications 24 V, 5.0 W
Power supply emf 24 V
Power supply maximum current 8.0 A
Length of each rod 12.5 m
Resistivity of rod metal 7.2 × 10–7 Ω m
One advantage of this system is that if one lamp fails then the other lamps in the circuit remain lit. Outline one other electrical advantage of this system compared to one in which the lamps are connected in series.
[1]
when adding more lamps in parallel the brightness stays the same ✔
when adding more lamps in parallel the pd across each remains the same/at the operating value/24 V ✔
when adding more lamps in parallel the current through each remains the same ✔
lamps can be controlled independently ✔
the pd across each bulb is larger in parallel ✔
the current in each bulb is greater in parallel ✔
lamps will be brighter in parallel than in series ✔
In parallel the pd across the lamps will be the operating value/24 V ✔
Accept converse arguments for adding lamps in series:
when adding more lamps in series the brightness decreases
when adding more lamps in series the pd decreases
when adding more lamps in series the current decreases
lamps can’t be controlled independently
the pd across each bulb is smaller in series
the current in each bulb is smaller in series
in series the pd across the lamps will less than the operating value/24 V
Do not accept statements that only compare the overall resistance of the combination of bulbs.
