Question

A voltmeter is used for measuring
A- electric current
B- resistance
C- voltage across resistance
D- magnetic field

Answer 1

Hint: A voltmeter is a device which is used in electronics and to measure some value in electric circuits. The function that it performs is hidden in its name itself.

Complete step by step answer:
One of the most commonly used components that we encounter in physics labs is Rheostat. A rheostat is a variable resistor and is a box consisting of many resistances and is used in labs. The resistance which is taken out from it gets attached into the circuit. Many of the times we are interested in finding out the potential drop across the resistance that we have attached in our circuit. Resistors can be of two types- variable and fixed, fixed resistor has a single fixed value of resistance, whereas a variable resistor has resistance value over a defined range. Let us check the options stated.
The first is electric current and we know ammeter is used to measure the electric current in the circuit. The second is resistance which can’t be the correct option. The fourth is the magnetic field which is a measured gauge. The only option that is left is voltage across resistance, hence voltmeter is used to measure the voltage across resistance.

Note:
A potentiometer is a three terminal variable resistor, but a rheostat is a two terminal variable resistor. One important point to make here is that potentiometers can work as a rheostat but the opposite of this cannot be done. Potentiometers are used to vary voltages while later for varying current. Galvanometer can be used for both the purpose to measure electric current as well as to measure the potential drop across the resistance.