Investigating series and parallel circuits|KS4 Physics|Teachit - Free Printable

This worksheet is designed to help students investigate series circuits, focusing on how the number of bulbs affects current and brightness, and whether current is "used up" in a circuit.

Since you've uploaded an image of the worksheet but not actual experimental data (like measured currents or observed brightness), I’ll guide you through how to solve each part based on scientific principles. You can use this explanation to fill in your results and answer the questions accurately.

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🔧 Task 1: Set up the circuits and measure current

There are three series circuits shown:
- Circuit 1: 1 bulb
- Circuit 2: 2 bulbs
- Circuit 3: 3 bulbs

All are connected in series with a battery and an ammeter (A) measuring current.

#### ✔ Expected Results (based on physics):

| Number of bulbs | Current (A) | Brightness of bulbs |
|------------------|-------------|----------------------|
| 1 | High (e.g., 0.6 A) | Very bright |
| 2 | Medium (e.g., 0.3 A) | Dimmer than one |
| 3 | Low (e.g., 0.2 A) | Even dimmer |

> ⚠️ Note: The exact values depend on the battery voltage and bulb resistance, but the trend is consistent.

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📌 Question 1: What effect has the number of bulbs on the current?

Answer:
As the number of bulbs increases, the total resistance in the circuit increases (since resistors in series add up). According to Ohm’s Law (I = V/R), if voltage stays constant and resistance increases, the current decreases.

👉 So, more bulbs → higher resistance → lower current.

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📌 Question 2: What effect has the current on the brightness of the bulbs?

Answer:
The brightness of a bulb depends on the power it uses:
Power = I² × R
So, as current decreases, the power dissipated by each bulb decreases → bulbs become dimmer.

👉 Therefore, lower current → dimmer bulbs.

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🔍 Is current used up in a circuit?

Now, set up a circuit with three bulbs in series and place the ammeter at four different positions:

- Position 1: After the battery
- Position 2: Between first and second bulb
- Position 3: Between second and third bulb
- Position 4: Before the battery (or after the last bulb)

#### ✔ Expected Results:

| Position of ammeter | Current (A) |
|---------------------|-------------|
| Position 1 | 0.2 A |
| Position 2 | 0.2 A |
| Position 3 | 0.2 A |
| Position 4 | 0.2 A |

> 💡 All readings should be the same because in a series circuit, the current is constant throughout.

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📌 Question 3: Is current used up in the circuit? Explain your answer.

Answer:
No, current is not used up in a circuit.

✔ Explanation:
Electric current is the flow of charge (electrons). In a series circuit, the same amount of charge flows through every component. Electrons don’t get "used up"—they transfer energy to the bulbs (causing them to glow), but they continue flowing around the circuit. The current remains constant at all points in a series circuit.

Think of it like water flowing through a pipe: the water doesn’t disappear when it goes through a water wheel—it just loses energy, but the flow rate stays the same.

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✔ Summary of Key Concepts:

| Concept | Explanation |
|--------|-------------|
| Series Circuits | Components are connected end-to-end; same current flows through all. |
| Current & Resistance | More bulbs = more resistance = less current. |
| Brightness | Depends on current and power; lower current = dimmer bulbs. |
| Current Conservation | Current is not used up—it's the same everywhere in a series circuit. |

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🛠 Tips for Doing the Lab:

- Use identical bulbs and batteries.
- Always connect the ammeter in series.
- Record current readings carefully.
- Observe brightness qualitatively (e.g., “bright”, “medium”, “dim”).

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Let me know if you'd like a completed version of the table with sample values or help with the parallel circuits section (which is likely on page 2/3)!