Question

For the circuits $A$ and $B$ as shown in the figure, identify the correct option.

• A. Circuit A is for accurate measurement of high resistance and B is for low resistance.
• B. Circuit A is for accurate measurement of low resistance and B is for high resistance.
• C. Both circuits can accurately measured high resistance only.
• D. Both circuits can accurately measured low resistance only.

Answer 1

Answer: (B)

In the given circuits, $A$ represents an ammeter, which is used to measured the current passing through the resistor it is not a low resistive device, so that it does not affect the circuit. It is connected in series with resistor.
Similarly, $V$ represents a voltmeter, which is used to measure the potential drop across the resistor. It is usually a high resistive device, so that the negligible current passes through it. Thus, does not affect no current passing through the resistor.
It is connected in parallel with to the resistor, This implies that, these devices are used measure. Current and voltage drop across a resistor, without actually affecting any of these quantities because of their addition in the circuit.
So, the given circuits $A$ and $B$ as shown below,

We can conclud that the circuit $A$ has been correctly connected. Therefore, it can be used to measure $R$ accurately, which can be calculated with the help of ammeter and voltmeter reading as,
$R=\frac{\text{voltage}(V)}{\text{ current }(I)}$ [From ohm's law]
However, when the arrangement of ammeter and voltmeter is as per given in circuit $B$. The circuit then is usually used for measuring higher resistance as compare to circuit $A$.