Question

To increase the range of a voltmeter we need to connect a suitable

• A. high resistance in series
• B. high resistance in parallel
• C. low resistance in series
• D. low resistance in parallel

Answer 1

The correct option is A

high resistance in series

Voltmeter:

1. A device that measures the potential difference, or voltages, between two locations in an electrical or electronic circuit is called a voltmeter.
2. To increase the range of the voltmeter, we need to connect a high resistance in series with the voltmeter.
3. The multiplier is a non-inductive high-value resistance connected in series with the instrument whose range is to be extended. The combination is connected across the circuit whose voltage is to be measured.

Explanation:

To measure current from electronic systems using an ammeter, the ammeter must be wired in series to that circuit, considering things connected in series encounter the same current as illustrated in figure (1).

To expand the ammeter range, users must connect an appropriate low resistance in a parallel combination. Diagrams will be used to assist us to comprehend this topic.

1. If we take the ammeter to be an ideal ammeter, then its internal resistance becomes zero. If a current (I) goes through, then $\mathrm{r}=0$ in figure (2) means that a portion of the current will pass through the ammeter and the portion will flow via the resistor.
2. If I is $100$ percent current flowing, and current is flowing throughout the resistor are $90$ percent and $10$ percent current throughout the ammeter, then perhaps the resistance must've been large. To enhance current flow inside an ammeter by $10$ percent, we must reduce the value of resistance such that less current flows through the resistance and more current flows through the ammeter. As a consequence, the ammeter will estimate greater current and exhibit deflection.
3. Essentially, whenever the resistance is large, it draws more current away from the voltage source, causing current to flow from point C to D. When we reduce the degree of resistance, current drags and more current flows through the ammeter. So, to improve the range of an ammeter, we should link low resistance in parallel so that the equivalent resistance is lower.
4. Similarly, to increase the range of the voltmeter a series resistor called a multiplier is connected in series to limit the meter current. The range of the voltmeter is the product of the multiplier resistance and the maximum meter current. So, to increase the range of voltmeter, multiplier resistance has to be increased.

Therefore, option (A) is the correct answer.