What is the SI unit of Galvanometer.

Options

A. `("div")/("volt")`
B. `("div")/(A)`
C. `("div")/(C )`
D. `("rad")/(V)`

Explanation

To determine the SI unit of a galvanometer, we need to understand its function and the quantities it measures. Here’s a step-by-step solution:

### Step 1: Understand the Function of a Galvanometer
A galvanometer is an instrument used to detect and measure small electric currents. It operates based on the principle that a current-carrying conductor experiences a magnetic field, which causes it to move.

**Hint:** Consider what a galvanometer measures and how it operates.

### Step 2: Identify the Key Quantity Measured
The primary measurement made by a galvanometer is the current sensitivity, which indicates how much the galvanometer's needle deflects in response to a given current.

**Hint:** Think about what the galvanometer's reading represents in terms of current.

### Step 3: Define Current Sensitivity
Current sensitivity (S) of a galvanometer is defined as the angle of deflection (θ) per unit current (I). Mathematically, it can be expressed as:
\[ S = \frac{\theta}{I} \]
where:
- \( S \) is the current sensitivity,
- \( \theta \) is the angle of deflection in radians,
- \( I \) is the current in amperes (A).

**Hint:** Recall the relationship between angle of deflection and current.

### Step 4: Determine the SI Unit of Current Sensitivity
From the formula \( S = \frac{\theta}{I} \), we can derive the SI unit of current sensitivity:
- The angle \( \theta \) is measured in radians (which is dimensionless in SI units).
- The current \( I \) is measured in amperes (A).

Thus, the SI unit of current sensitivity becomes:
\[ \text{SI unit of current sensitivity} = \frac{\text{radians}}{\text{amperes}} = \text{radians per ampere} \]

**Hint:** Consider how units combine in the formula for current sensitivity.

### Step 5: Conclusion
Therefore, the SI unit of a galvanometer, specifically in terms of its current sensitivity, is expressed as radians per ampere (rad/A).

**Final Answer:** The SI unit of a galvanometer is radians per ampere (rad/A).

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