Question

milestone mastery: lets get hands-on with science!
use the model to answer the following question. what is a disadvantage of this model?
image of a circuit with bulbs and a battery
a if more light bulbs are added, resistance increases which causes the current, and the brightness of the light bulbs to decrease.
b if more light bulbs are added, resistance decreases, and the brightness of the light bulbs decrease.
c if more light bulbs are added, resistance increases which causes the current and the brightness of the light bulbs to increase.
d if more light bulbs are added, resistance decreases, the current and the brightness of the light bulbs increases.

use the scenario to answer the following question.
you are presented with an antique dollhouse that contains five light bulbs, a switch, and a 1.5 - volt battery. the wires of the circuit are hidden from your view so that you cannot see how the bulbs are connected to the battery. you are able to turn on the lights and they are all working. the switch turns all of them on or off together.
how could you determine the type of circuit used in this model?
select the two best answer choices.
a. if all the bulbs are glowing with equal brightness, it is a series circuit because each bulb in a series circuit has a different resistance.
b. if all the bulbs are glowing with equal brightness, it is a parallel circuit because each bulb in a parallel circuit has its own path to the battery.
c. if all the bulbs are glowing with less brightness, it is a parallel circuit because each bulb in a parallel circuit has its own path to the battery.
d. if you unscrew one bulb and all the others stay lit, it is a series circuit because each bulb in a series circuit has to share the same current.
e. if you unscrew one bulb and all the others stay lit, it is a parallel circuit because each bulb in a parallel circuit has its own path to the battery.

Explanation:

For the first question (disadvantage of the model with light bulbs):

• In a series circuit, adding more resistors (light bulbs) increases total resistance ($R_{total}=R_1 + R_2+\dots$). By Ohm's law ($I = \frac{V}{R}$), with constant voltage (battery), current $I$ decreases. Brightness depends on power ($P = I^2R$ or $P=\frac{V^2}{R}$); for series, $P$ per bulb decreases as $I$ drops. So option A is correct as adding bulbs increases resistance, decreases current and brightness.

For the second question (determine circuit type):

• Option B: In parallel circuits, each bulb has the same voltage (battery voltage). If bulbs are identical, they have equal resistance, so equal current ($I=\frac{V}{R}$) and equal brightness. So equal brightness can indicate parallel (since in series, if bulbs are identical, they also have equal brightness, but the reasoning here: parallel has each bulb its own path, so same voltage leads to equal brightness if bulbs are same. The option's reasoning about "own path" connects to parallel's voltage equality for same bulbs).
• Option E: In parallel, each bulb has its own branch. Unscrewing one bulb (opening its branch) doesn't affect other branches (current still flows through them). In series, unscrewing one breaks the circuit. So if other bulbs stay lit, it's parallel, which matches option E's reasoning.

Answer:

First question: A. If more light bulbs are added, resistance increases which causes the current, and the brightness of the light bulbs to decrease.
Second question: B. If all the bulbs are glowing with equal brightness, it is a parallel circuit because each bulb in a parallel circuit has its own path to the battery. ; E. If you unscrew one bulb and all the others stay lit, it is a parallel circuit because each bulb in a parallel circuit has its own path to the battery.