Question

A cell, an ammeter and a voltmeter are all connected in series. The ammeter reads a current $I$ and the voltmeter reads a potential difference $V$. If a torch bulb is connected across the voltmeter, then,
(A) both $I$ and $V$ will increase
(B) both $I$ and $V$ will decrease
(C) $I$ will increase but $V$ will decrease
(D) $I$ will decrease but $V$ will increase

Answer 1

Hint
To solve this problem we have to know about the series and parallel connection formula for resistance. Because in addition to this circuit, the torch bulb is connected. The torch bulb acts as a resistor, so we have to know about the series and parallel connection formula for the resistor.

Complete step by step solution
The ammeter is a device which is used to determine the amount of current flows in the circuit. And the voltmeter is the device which is used to determine the potential difference across any two points. In this circuit, certain components allow the electric current to flow and some components resist the electric current to flow. The motion of electrons constitutes the flow of electric current. These electrons are not free to move within a conductor.

If the motion of electron is retarded by some conductor is called resistor. And also, the component which has some applicable resistance is called a resistor. A component of given size which offers low resistance is called a good conductor. If the component has resistance it is a poor conductor. An insulator is a component which has high resistance. If the torch bulb is connected across the voltmeter, the torch bulb is a component of very low resistance. Thus, the current $I$ will increase and the voltage or potential difference $V$ will decrease.
Hence, the option (C) is correct.

Note
It is very important to know about the resistance and the relation between the resistance and the current and the relation between the resistance and the voltage. And to know about the potential difference and the function of a torch bulb whether it acts as a conductor or resistor.