Question

Name an instrument used for measuring electric potential difference by drawing a diagram. Show how this instrument is connected in an electric circuit. Why does this practically not consume any electric energy from the electric current?

Answer 1

Hint: Electric potential difference is defined as the difference between the final and the initial place or location or in other words it can be defined as the amount of work to carry a unit charge from one point to another in an electric field.

Complete solution:
The instrument which is used for measuring electric potential is voltmeter. As the name suggests it is an instrument that measures electric potential. The voltmeter was invented by Andrew Kay in 1954.
          

There are two types of voltmeter one is Analog voltmeter and another is Digital voltmeter. In analog voltmeter there is a needle which gets deflected whenever the device detects voltage while a digital voltmeter gives a numeric display of the voltage passing through it by using an analog to digital converter. Nowadays the voltmeter can measure both dc sinusoidal and ac sinusoidal voltages. In the diagram below there is a schematic representation of the voltmeter.

Here the voltmeter is connected to the circuit to measure the voltage that the voltage source is supplying. The reason that voltmeter does not consume any electrical energy form the circuit in the form of electrical current is because the voltmeter has a very high resistance in it therefore the current cannot pass through it.

Note: Essentially voltmeter or potentiometer does not measure electric potential but it actually measures electric potential difference. To measure the voltage by voltmeter we need to keep it in parallel with the circuit, as we know that in parallel combination the voltage remains the same.