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What is the Current in Ammeter Connected in Parallel?

If an Ammeter is Connected in Parallel with Load, What is the Deflection?

Basic Electrical Engineering Interview Question Series: An Ampere meter is connected in parallel with the 100 ohms load and 220V AC Supply. What is the current value flowing through ammeter?

What is the Current in Ammeter Connected in Parallel


Short Answer: Boom and Ammeter will blow if there is no fuse or circuit breaker.

Explanatory Answer:

Ammeter (short version of Ampere meter) is always connected in series due to the low internal resistance and proper current measurement as compared to voltmeter which is connected in parallel. If an ammeter is connected in parallel, the circuit current will chose a least resistive path for flow of electron i.e. current will ignore the load in resistance and flow the ammeter circuit which may destroy the ampere meter.

As shown in the fig above, ampere meter is connected such a way like a short circuit path in the basic circuit.

Now, If we analyze the circuit where ampere meter is connected in parallel with the supply voltage and load. As we know that current always chose a low resistance path to flow, hence the current will bypass the 100 Ohms (current will not flow through the 100 Ohms) load in the circuit and start to flow through the ampere meter due to low internal resistance.

The current flow in this basic circuit is shown with the blue line with arrow around the circuit.

If an Ammeter is Connected in Parallel with Load, What is the Deflection

Theoretically, the flowing amount of current through the ammeter circuit is infinite if we neglect the internal resistance of ammeter.

According to the ohm’s law

I = V / R

Putting the values

I = 220V / 0Ω

I = Infinite.

As a result:

  • Current will be infinite due to short circuit. 
  • Ammeter may start to smoke and burn if there is no fuse in the circuit.

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  1. Thank you so much for the Q/A answer series. Clear and nice explanation. Please add more question and answers like these in future to clear the basic concepts of newbies like me.

  2. Came in trade late age 36 have 11 years experience now but company I work for I requiring us to pass nccer to continue working for them and I’m having trouble there is alot to remember is there any tips or areas I need to study more on then others

  3. Current through the ammeter is a function of the internal impedance (resistance) of the ammeter. The false assumption that the resistance is zero is not accurate, the ammeters are constructed with the minimum possible internal impedance to minimize the effect on the integrity of the circuit. But do have some resistance. Hence there will be some small current flow through the load (100 ohms)

    1. Ammeter is having very low impedance hence maximum current will flow through ammeter and will destroy the ammeter, whereas negligible current will flow through load. Protection fuse will blow off.

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