In which one of the following situations does a conventional electric current flow due north?

Options

A. Protons in a beam are moving due south
B. A water molecule is moving due north
C. Electrons in a beam are moving due south
D. Electrons a wire connected to a battery are moving from south to north

Answer

To determine in which situation a conventional electric current flows due north, we need to analyze the options provided based on the definition of conventional current. Conventional current is defined as the flow of positive charge, which is opposite to the flow of electrons.

### Step-by-Step Solution:

1. **Understand Conventional Current**:
- Conventional current is defined as the flow of positive charge from the positive terminal to the negative terminal of a battery. This means that if positive charges are moving in a certain direction, that direction is considered the direction of conventional current.

2. **Analyze the Options**:
- Let's evaluate each option provided in the question:

**Option 1**: A beam of protons moving due south.
- Protons are positively charged particles. If they are moving south, the conventional current also flows south.
- **Conclusion**: This option is incorrect.

**Option 2**: A water molecule moving due north.
- Water molecules are neutral and do not carry charge. Therefore, they do not contribute to the flow of current.
- **Conclusion**: This option is incorrect.

**Option 3**: Electrons in a beam moving due south.
- Electrons are negatively charged particles. If they are moving south, the conventional current flows in the opposite direction, which is north.
- **Conclusion**: This option is correct.

**Option 4**: Electrons in a wire connected to a battery moving from south to north.
- Here, electrons are moving from south to north, which means the conventional current flows from north to south (the opposite direction).
- **Conclusion**: This option is incorrect.

3. **Final Answer**:
- The only situation where the conventional current flows due north is when electrons in a beam are moving due south.

### Summary:
The correct answer is **Option 3**: Electrons in a beam are moving due south, which results in conventional current flowing due north.