Understanding a Voltmeter

The other day I showed my 6 year old how to use a voltmeter.  I have a simple voltmeter at home to check the voltage on batteries.  It comes in very handy because sometimes a battery operated object may stop working due to a dead battery or due to something else.  The voltmeter confirms whether it is an issue with the battery or with something else.

Our voltmeter at home

We recently used the voltmeter when checking the batteries in the fire alarms in the house.  We had a slowly beeping fire alarm the other day, signaling that the battery was low.  Before tossing the battery we checked it to make sure the battery was indeed dead.  The voltmeter showed a reading of 8.20 Volts for a 9 Volt battery.  So although the battery was still working, it was near the end of its life.  We checked the other fire alarm batteries to make sure they were all at or above 9 volts.  It's a good thing we checked this because another battery was near 8.20 Volts, meaning that it was only a matter of time before it started beeping too.

I showed my daughter how to turn the voltmeter on and how to test the voltage of the battery.  She thought it was cool to take the leads of the voltmeter and touch them to different parts of the battery!