Question

A circuit contains two light bulbs connected in parallel. What would happen to the brightness of each light bulb if two more light bulbs were added in parallel to the first ones?
A. The brightness of each bulb would decrease because the total resistance of the circuit would decrease.

B. The brightness of each bulb would increase because the total resistance of the circuit would increase.

C. The brightness of each bulb would remain the same even though the total resistance of the circuit would decrease.

D. The brightness of each bulb would remain the same even though the total resistance of the circuit would increase.

Answer 1

In order to say definitely what would happen, we need to make sure that
the light bulbs are the only items connected to the battery or power supply.
What I mean is:  You can't start out with, say, a string of Christmas tree
lights, and at some point in the string, there's an extra little bulb in parallel
with one of the lights in the string.  If that's the situation ... if there's anything else in the circuit besides the two light bulbs in parallel ... then we'd need
more information in order to predict what happens when we make changes
to that part of the circuit.

So the whole circuit consists of: 
Two light bulbs in parallel, connected to a battery.  That's all.

Now, we connect two MORE light bulbs in parallel with the first ones.
Now we have FOUR light bulbs, all in parallel, connected to the battery.

-- The battery would see the total resistance of the circuit DECREASE.
(An electron that leaves one terminal of the battery now has 4 ways to
reach the other side of the battery, instead of just two.  It's easier for
electrons to get there, so more of them make the trip every second.)

-- Did you hear that ?  "More electrons make the trip every second."
That means there's more current leaving the battery.

-- IF the battery or power supply is able to deliver the increased current,
then the original devices ... the original two light bulbs ... don't even know
that anything has happened.  Their brightness doesn't change.

-- Choice-C  says this.
_______________________________

I just told you that connecting more stuff in parallel makes no difference
to the devices that are already there.  If that sounds weird to you, then
let me tell you this:

EVERYTHING in your house is in parallel with everything else ! 
Every light, kitchen appliance, motor, heater, electric furnace, radio,
air conditioner, phone charger, TV, computer, mixer, microwave  ...
everything that plugs into a socket in the wall ... is in parallel with
everything else that you plug in.

When you plug in something new, or turn on something that was off,
it should have no effect on the things that were already running.
(If it does ... if, say,  the lights in kitchen go dim when you turn on
the microwave ... then the wiring in your house is a little bit skimpy
for running all the things that we run in our houses now.)

Answer 2

Answer;

C. The brightness of each bulb would remain the same even though the total resistance of the circuit would decrease.

Explanation;

-If light bulbs are connected in parallel to a voltage source, the brightness of the individual bulbs remains more-or-less constant as more and more bulbs are added to the circuit.

-The current increases as more bulbs are added to the circuit and the overall resistance decreases. In addition, if one bulb is removed from the circuit the other bulbs do not go out. Each bulb is independently linked to the voltage source

Answer 3

Answer;

C. The brightness of each bulb would remain the same even though the total resistance of the circuit would decrease.

Explanation;

-If light bulbs are connected in parallel to a voltage source, the brightness of the individual bulbs remains more-or-less constant as more and more bulbs are added to the circuit.

-The current increases as more bulbs are added to the circuit and the overall resistance decreases. In addition, if one bulb is removed from the circuit the other bulbs do not go out. Each bulb is independently linked to the voltage source