Dimming the Lights

 

Based on Starting Point Activity p. 353

 

Purpose:

  1. How does one electrical device affect another?
  2. What is the best way to connect more than one light bulb with another electrical device in a circuit?
  3. To examine differences between Series and Parallel circuits.
  4. To examine the current in different places in Series and Parallel circuits.
  5. To examine the effect of switch placement in Series and Parallel circuits.

 

Equipment:

Battery Eliminator set at 6V

1 Ammeter

1 switch

5 of 6V bulbs in holders

14 alligator clip connecting wires

 

Procedure:

 

Part 1:  Series Circuit

 

Connect the first light bulb, (the other bulbs will act as extra resistors and added in next steps), the switch and the ammeter and the battery eliminator one after the other as shown in the diagram below.  The ammeter and switch will be moved at points in the activity as shown in the data chart below.  You must compare the bulb brightness from one set up to the next at each step in the lab.

 

 

Ammeter may be attached at the 500mA post.  Remember to record the date in Amps.

 

Number of Bulbs in Circuit

Bulb Brightness

Current (A)

What happens to bulbs when the switch is opened?

Bulb 1

 

 

 

 

Bulb 1, 2

 

 

 

 

Bulb 1, 2, 3

 

 

 

 

Bulb 1, 2, 3, 4

 

 

 

 

Bulb 1, 2, 3, 4, 5

 

 

 

 

Move ammeter and switch to between Bulb 1 and Bulb 2

Bulb 1, 2, 3, 4, 5

 

 

 

 

Continued … what happens when a bulb is unscrewed?

Light Bulb 1 is unscrewed

 

Light Bulb 2 is unscrewed

 

Light Bulb 5 is unscrewed

 

 

Part 2:  Parallel Circuit

 

Connect the light bulbs, the switch, the ammeter and the battery eliminator as shown in the diagram below.  To make new pathways clip the wires to one another as shown.  The ammeter and switch will be moved at points in the activity as shown in the data chart.  You must compare the bulb brightness from one set up to the next at each step in the lab.

 

 

 

Ammeter must be attached at the 5A post.

 

Number of Bulbs in Circuit

Bulb Brightness

Current (A)

What happens to bulbs when the switch is opened?

Bulb 1

 

 

 

 

Bulb 1, 2

 

 

 

 

Bulb 1, 2, 3

 

 

 

 

Bulb 1, 2, 3, 4

 

 

 

 

Bulb 1, 2, 3, 4, 5

 

 

 

 

Move ammeter and switch to after Bulb 1

Bulb 1, 2, 3, 4, 5

 

 

 

 

Move ammeter and switch to after Bulb 2

Bulb 1, 2, 3, 4, 5

 

 

 

 

…What happens when a bulb is unscrewed?

Light Bulb 1 is unscrewed

 

Light Bulb 2 is unscrewed

 

Light Bulb 5 is unscrewed

 

 

 

What did you discover?

 

Which method of connecting a circuit is better for household circuits?  Explain how you made your choice?

 

 

 

 

 

 

 

 

 

Analyze:

 

Series Circuits

 

  1. What happens to the current as you add a larger amount of resistance, that is as you add more light bulbs with longer amounts of wire?

 

 

 

 

  1. What happens to the brightness of the bulbs as you add a larger amount of resistance?  Why?

 

 

 

 

  1. Are all bulbs the same brightness?  Explain your answer.

 

 

 

 

 

  1. What happens to the current when either Bulb 1 or Bulb 2 is unscrewed?  Explain your answer

 

 

 

 

  1. Is the current the same everywhere in the circuit?  Explain.

 

 

 

 

  1. Name some examples where this type of circuit may be used.

Parallel Circuits

 

  1. What happens to the current as you add a larger amount of resistance, that is as you add more light bulbs with longer amounts of wire?

 

 

 

 

  1. What happens to the brightness of the bulbs as you add a larger amount of resistance?  Explain.

 

 

 

 

 

 

  1. Are all bulbs the same brightness?  Explain.

 

 

 

 

 

 

  1. Compare the current in the first part of the circuit to the current measured by the ammeter when it was moved to be after bulb 1.  Explain. 

Also compare the current in the first part of the circuit to the current measured by the ammeter when it was moved to be after bulb 2.  Explain.

Is the current the same everywhere in the circuit?  Discuss (on paper)

 

 

 

 

 

 

 

 

 

  1. What happens to the current when bulb 1 is unscrewed?  Explain.

What happens to the current when bulb 2 is unscrewed?  Explain.

 

 

 

 

 

 

 

  1. Name some examples where this type of circuit may be used.