An analog ammter and voltmeter of suitable ranges are to be used to measure the current and voltage of an..?

Question

electric lamp. If a mistake was made and the meters were interchanged, what will happen?

Answer 1

the ammeter (now in parallel) would read nothing,

The volt meter (now in series) would read the supply voltage

( the potential difference across the two points it is connected to)

Answer 2

If the meters are both connected at the same time as you imply that they are.  Only minimum current will flow in the circuit since the voltmeter is high resistance. (it will measure the source voltage).  

However if the voltmeter is disconnected and the ammeter is connected in parallel across the lamp you will create a short circuit of the power source and probably blow the internal fuse in the ammeter.

Answer 3

A Ammeter acts like a short to the circuit. It usually is limited in the ammount of current it passes. The meter can be damaged if placed across the source of power greater than its capability.

A Voltmeter measures the voltage across an item. If placed into the circuit in place of an ammeter, it would act like a open, and no current flow will occur. The better Voltmeters have a FET front end which has little impact to the circuit being measured.

Answer 4

I assume the lamp is connected to a battery or to the wall outlet, otherwise nothing will happen.

But if it is, connecting an ammeter directly across a powerful battery or the wall outlet will result in one or more of the following: a burned out ammeter, a blown fuse or breaker, or lots of smoke.

Connecting a voltmeter in series with the load will result in the voltmeter reading the battery or AC line voltage and no damage will occur.