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VOLTAGE DIVIDER CIRCUIT

Use Ohms law to determine a rheostat’s resistance by measuring voltage

Suitable For

Grade 7

Difficulty

1

Time Required

 <2 Days

Supervision

Advised

What’s it about?

A ‘resistor’ is an electrical component that ‘resists’ or restricts the flow of electrons through it. A ‘rheostat’, also called a ‘variable resistor’, is a switch that allows us to change the amount of resistance and the flow of electrical current experienced, without interrupting the flow of the current.

When several resistors are placed ‘in series’ within an electrical circuit, each resistor causes the total ‘voltage’ supply in a circuit to drop partly according to its ‘resistance’. Hence, two resistors of equal value connected in series in a circuit with a 6-V battery will have a voltage of 3-V over each and a 6-V total voltage over both resistors.

This resistor arrangement is called a ‘voltage divider’ circuit. In the following science experiment, use a voltage divider circuit in conjunction with ‘Ohm’s law’ to determine the resistance of a ‘rheostat’, by measuring the voltage change over the ‘rheostat’:

Topics covered

Resistance, In Series, Variable resistor or ‘Rheostat’, Ohm’s law

What will I need?

  • INSULATED WIRE WITH ALLIGATOR CLIPS
  • 2X 100-OHM RESISTORS
  • 100-OHM VARIABLE RESISTOR
  • WIRE CUTTERS
  • 6-VOLT BATTERY
  • AM / VOLT / OHMMETER

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.

This science experiment works because in a voltage divider circuit, each resistor voltage drop will be some fraction or percentage of the total voltage, hence the name voltage divider given to this circuit. This fractional value is determined by the resistance of the particular resistor and the total resistance. If a resistor drops 50% of the total battery voltage in a voltage divider circuit, that proportion of 50% will remain the same as long as the resistor values are not altered. So, if the total voltage is 6 volts, the voltage across that resistor will be 50% of 6, or 3 volts. (Read more about this in the e-book work sheet…)

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