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DIM THE LIGHTS, QUE THE MUSIC…

Make a working rheostat to control the flow of electrical current

Suitable For

Grade 4

Difficulty

2

Time Required

 <2 Days

Supervision

Required

What’s it about?

A ‘rheostat’, also called a ‘variable resistor’, is a switch that allows us to change the amount of resistance the flow of electrical current experience, without interrupting the flow of the current. This is very useful to many electrical appliances such as an electrical motor which speed can be controlled, the volume control on a CD player or a dimmer switch that you might have in your home, which allows you to control the level of light in a room.

A ‘rheostat’ simply works by passing electrical current through a poor conductor as you will see in this science experiment:

Topics covered

Rheostat, Conductor

What will I need?

  • 9-VOLT BATTERY
  • SOFT PENCIL
  • 9-VOLT LIGHT BULB IN HOLDER
  • COPPER WIRE
  • STICKY TAPE
  • WIRE CUTTERS
  • CORRUGATED CARDBOARD

Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

In this science experiment we made our own rheostat by using the soft graphite in a pencil which is a poor conductor of electricity. The farther the free wire end is moved from where the first wire is fixed to the graphite end, the more of this ‘poor conductor’ is placed between the flow of current and the more resistance the flow will experience. The light dims as the resistance increases and brightens as the resistance decreases.

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