The range of ammeter can be increased by

Options

A. decreasing shunt
B. increasing shunt
C. changing scale
D. none of these

Answer

To increase the range of an ammeter, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Ammeter**: An ammeter is a device used to measure electric current. It is designed to measure small currents, and its range can be limited based on its internal resistance and the maximum current it can handle.

2. **Using a Shunt Resistor**: To increase the range of the ammeter, we can connect a shunt resistor in parallel with it. A shunt resistor allows a portion of the current to bypass the ammeter, thus enabling it to measure higher currents without being damaged.

3. **Calculating the Total Current**: When a shunt resistor is connected in parallel, the total current (I) flowing through the circuit is divided between the ammeter (i) and the shunt (ij). The relationship can be expressed as:
\[ I = i + ij \]
Here, \(i\) is the current through the ammeter, and \(ij\) is the current through the shunt.

4. **Adjusting the Shunt Resistance**: To increase the range of the ammeter, we need to adjust the value of the shunt resistor. By decreasing the resistance of the shunt (S), we can allow more current to flow through it, which effectively increases the total current that can be measured by the ammeter without exceeding its limit.

5. **Understanding Equivalent Resistance**: The equivalent resistance (R_eq) of the system with the shunt connected in parallel can be calculated using the formula:
\[ R_{eq} = \frac{R \times S}{R + S} \]
where R is the internal resistance of the ammeter. By decreasing the value of S (the shunt resistance), the equivalent resistance R_eq decreases, allowing more current to flow through the ammeter.

6. **Conclusion**: Thus, to increase the range of the ammeter, we can decrease the shunt resistance. This allows the ammeter to measure higher currents without being damaged.

### Final Answer:
The range of the ammeter can be increased by **decreasing the shunt resistance**.

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