Question

The diagram shows a circuit containing a cell, an ammeter, a lamp and a variable resistor.
The resistance of the variable resistor is increased.
What happens to the ammeter reading and what happens to the brightness of the lamp?

	ammeter reading	lamp brightness
A	decreases	decreases
B	decreases	increases
C	increases	decreases
D	increases	increases

• A. A
• B. B
• C. C
• D. D

Answer 1

The correct option is A A

As we know that

The current through the circuit , $I=\frac{E}{R}$

Where, $E$ is the e.m.f of the cell

and $R$ is the equivalent resistance of the circuit.

Now in the given circuit As the resistance of variable resistor increases, the current $I$ through the circuit will decreases

Hence the ammeter reading will decreases and the lamp brightness will also decreases