Light bulbs in parallel and series

In summary: And therefore, wouldn't the power drawn by the battery also be twice that of the first circuit?In summary, the brightness of the lightbulbs in circuit 1 is brighter than the two in parallel in circuit 2, which have equal brightness. If one lightbulb is removed from circuit 2, the remaining bulb will have the same brightness as the lightbulb in circuit 1. This is because in parallel circuits, the voltage and current are the same for each component, but in series circuits, the total voltage and current is divided among the components. Therefore, removing one bulb in circuit 2 does not affect the current and voltage in the remaining bulb, resulting in the same brightness as the bulb in circuit 1.
  • #1
meadow
19
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Q: You have a light bulb in series with a battery to make a complete circuit. Then you have another circuit with two light bulbs in parallel connected to a battery. The lightbulbs in all the circuits are identical and the batteries are the same in the two circuits. Before working with these circuits, you are asked to make some predictions: (a.) What is the brightness of the bulbs in circuit 2 (the light bulbs in parallel) relative to each other and to the bulb in circuit 1? (b.) If one of the bulbs is removed from circuit 2, how will the brightness of the other bulb be affected? Does it matter which bulb is removed?

I think that (a.) the light bulb in series with the battery is brighter than the two in parallel and they are as bright as each other.
(b.) If one is removed, the bulb will become as bright as the bulb in circuit 1; and that it does not matter which is removed.
Am I right in thinking this? And can someone explain this more to me?
 
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  • #2
meadow,

FYI, I've moved this thread over to Introductory Physics.

On to your question:

Am I right in thinking this?

You sure are!

And can someone explain this more to me?

Yes, but rather than type it all out I am going to ask you some leading questions. You don't have to answer them of course, but if you do then you will be well on your way towards expressing your thoughts in the same way that a physicist would.

Let the voltage of the battery in each circuit be [itex]V[/itex] and let the resistance of each bulb be [itex]R[/itex] and the current drawn from the battery be [itex]I[/itex]. The answers to all the questions I am going to ask should be put in terms of these three symbols.

1.) In the first circuit, what is the voltage [itex]V_L[/itex] across the lightbulb?

2.) In the first circuit, what is the current [itex]I[/itex] drawn by the lighbulb?

3.) In the first circuit, what is the power [itex]P_L[/itex] drawn by the lightbulb? You should have an equation for power.

4.) In circuit 2, what is the voltage [itex]V_L[/itex] across each lightbulb? (Hint: The two voltages are the same. Can you explain why?)

5.) In circuit 2, what is the current [itex]I_L[/itex] drawn by each lightbulb? (Hint: The two currents are the same. Can you explain why?)

6.) In circuit 2, what is the power [itex]P_L[/itex] drawn by each battery? (Hint: If you get 4 and 5, then it should be clear that the two values of the power are the same).
 
  • #3
Tom Mattson said:
4.) In circuit 2, what is the voltage [itex]V_L[/itex] across each lightbulb? (Hint: The two voltages are the same. Can you explain why?)

5.) In circuit 2, what is the current [itex]I_L[/itex] drawn by each lightbulb? (Hint: The two currents are the same. Can you explain why?)

6.) In circuit 2, what is the power [itex]P_L[/itex] drawn by each battery? (Hint: If you get 4 and 5, then it should be clear that the two values of the power are the same).

But in circuit two, if the voltage and current drawn by each lightbulb is the same, wouldn't the total voltage and current in the circuit be twice that of the first path, since there are two lightbulbs?
 

FAQ: Light bulbs in parallel and series

1. What is the difference between light bulbs connected in parallel and series?

In a parallel circuit, the light bulbs are connected to the same power source but have separate branches, allowing each bulb to receive the full voltage. In a series circuit, the light bulbs are connected in a single loop, sharing the same voltage and resulting in a decrease in brightness for each bulb added.

2. Which circuit is more efficient for lighting multiple bulbs?

A parallel circuit is more efficient for lighting multiple bulbs because each bulb receives the full voltage, ensuring that they all emit the same level of brightness. In a series circuit, the voltage is divided between the bulbs, resulting in a decrease in brightness.

3. Can I mix different types of light bulbs in a parallel or series circuit?

Yes, you can mix different types of light bulbs in both parallel and series circuits. However, it is important to consider the voltage and wattage of each bulb to ensure that the circuit is not overloaded.

4. Which circuit is safer to use?

A parallel circuit is generally considered safer to use because if one bulb burns out, the rest will still continue to function. In a series circuit, if one bulb burns out, the entire circuit will be affected and could potentially cause a power surge.

5. How do I calculate the total resistance in a parallel or series circuit?

In a parallel circuit, the total resistance can be calculated by adding the reciprocals of each individual resistance and then taking the reciprocal of the sum. In a series circuit, the total resistance is simply the sum of all the individual resistances.

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