Which of the follwing characteristies of electrons determines the current in a conductor?

Options

A. Drift velocity alone
B. Thermal velocity alone
C. Boh drift velocity and thermal velocity
D. Neither drift nor thermal velocity

Explanation

To determine which characteristic of electrons determines the current in a conductor, we can analyze the relationship between current and the motion of electrons.

### Step-by-Step Solution:

1. **Understanding Current**:
Current (I) in a conductor is defined as the rate of flow of charge. Mathematically, it can be expressed as:
\[ I = \frac{Q}{t} \]
where \(Q\) is the charge and \(t\) is the time.

2. **Charge Carriers**:
In conductors, electrons are the primary charge carriers. The flow of these electrons constitutes the electric current.

3. **Drift Velocity**:
The average velocity that an electron attains due to an electric field is called drift velocity (\(V_D\)). It is this velocity that contributes to the net flow of charge in the conductor.

4. **Expression for Current**:
The current can also be expressed in terms of the number of charge carriers (n), charge of each carrier (e), cross-sectional area (A), and drift velocity (V_D):
\[ I = n \cdot e \cdot A \cdot V_D \]
From this equation, we can see that the current (I) is directly proportional to the drift velocity (\(V_D\)).

5. **Thermal Velocity**:
Thermal velocity refers to the random motion of electrons due to thermal energy. While electrons do have thermal motion, it does not contribute to the net current because it averages out to zero in the absence of an electric field.

6. **Conclusion**:
Since the expression for current includes drift velocity and not thermal velocity, we can conclude that the characteristic of electrons that determines the current in a conductor is the **drift velocity alone**.

### Final Answer:
The characteristic of electrons that determines the current in a conductor is **drift velocity alone**.

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