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How to Make a Watt Meter

A number of key macroscopic quantities are useful to provide measurements in electrical circuits. Voltage is the potential energy per unit charge and is thus a measure of how much energy electrons have. Current is a scaled measure of electron velocity. The product of voltage and current gives the power that is the amount of energy that is used per unit time. A Watt is a unit of power. You can make a simple Watt meter from a voltmeter -- device that measures voltage -- and an ammeter -- a device that measures current.

Things You'll Need

Voltmeter
Ammeter
Banana cables
Alligator clips

Instructions

- 1
  Ensure the device whose power you are measuring is switched off. Plug a banana lead into the positive and negative terminals of the voltmeter. Connect an alligator clip on the end of each cable. Using the alligator clips, connect the voltmeter to part of the circuit where the power is required.
- 2
  Plug a banana lead into each terminal on the ammeter. Place an alligator clip on the end of each lead. Using the alligator clips, connect the ammeter to the circuit, in the same place where the voltage leads are.
- 3
  Switch on the electrical device whose power you are measuring. Switch on the ammeter and voltmeter. You can now read the voltage and current on the voltmeter and ammeter, respectively. In order to get the current, multiply the voltage in Volts by the current in Amps. The result is the power, which is measured in Watts.

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