A microammeter has as resistance of `100 Omega` and full scale range of `50 muA`. It can be used as voltmeter or as a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combinations

Options

A. 50 V range with 10 `kOmega` resistance in series
B. 10 V range with 200 `kOmega` resistance in series
C. 10 mA range with `1Omega` resistance in parallel
D. None of the above

Answer

To solve the problem of converting a microammeter into a voltmeter or a higher range ammeter, we need to follow these steps:

### Step 1: Understand the given parameters
- The resistance of the microammeter (R_m) = 100 Ω
- The full-scale range of the microammeter (I_g) = 50 µA = 50 x 10^-6 A

### Step 2: Determine the formula for additional resistance
To convert the microammeter into a voltmeter, we need to add a resistance (R) in series. The formula to calculate the additional resistance needed is given by:

\[ R = \frac{V}{I_g} - R_m \]

Where:
- V is the voltage range we want to measure.
- I_g is the full-scale current of the microammeter.
- R_m is the resistance of the microammeter.

### Step 3: Substitute the known values into the formula
We can rearrange the formula to find R for a specific voltage V. Let's consider a few voltage ranges.

#### Example Calculation for V = 10V
Substituting V = 10V into the formula:

\[ R = \frac{10}{50 \times 10^{-6}} - 100 \]

### Step 4: Calculate the resistance
Calculating the first part:

\[ \frac{10}{50 \times 10^{-6}} = \frac{10}{0.000050} = 200,000 \, \Omega = 200 \, k\Omega \]

Now, substituting back into the equation:

\[ R = 200,000 - 100 = 199,900 \, \Omega \approx 200 \, k\Omega \]

### Conclusion
Thus, to convert the microammeter to read up to 10V, we need to add a resistance of approximately 200 kΩ in series.