Another curcuit question?

Question

Which of the following curcuits can be used to test whether or not a wire of a laminated heating element is cut internally?

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Answer 1

Either a watt meter in series with the AC power cord with plug into wall and turned on to hot, or with the unit unplugged measure the resistance between the hot and neutral spades of the power plug with the thermostat control turned on to hot.  

Watt meter should read what the unit wattage is rated for.

The ohmmeter should read a low resistance, less than 100 ohms, not an open circuit.

Answer 2

I suppose B is closest.

Answer 3

Let's do this by figuring out which ones it isn't:

A: Does a heating element supply current? If not, will the Amp meter read anything, open or not?

B: Does a heating element supply voltage? If not, will the Volt meter read anything, open or not?

C: A battery is supplying voltage to the Amp meter and heating element in series. In a series circuit, there is one path for current so current in both the Amp meter and the heating element is the same. So if the heating element is OK, current flows through both the Amp meter and heating element. If the heating element is cut, no current flows through either.

D: With the Amp meter and heating element in parallel, current in the Amp meter is (in an ideal circuit) independent of current in the heating element. So in an ideal circuit, there will be no change in the Amp meter regardless of the state of the heating element.

Which answer do you think is correct after reading those?

Answer 4

B.  An ampmeter must be in series to measure current flow.