Which of the following will work best as a tester for electric current ?

Options

A. Bulb
B. LED
C. CFL
D. Magnetic compass

Answer

To determine which of the following options works best as a tester for electric current, we will analyze each option: bulb, LED, CFL, and magnetic compass.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **Bulb**: A traditional incandescent bulb can indicate the presence of current by lighting up.
- **LED**: An LED (Light Emitting Diode) can also light up when current flows through it, indicating the presence of current.
- **CFL**: A Compact Fluorescent Lamp (CFL) works similarly to a bulb but requires a certain amount of current to start and may not indicate low current effectively.
- **Magnetic Compass**: A magnetic compass can indicate the presence of electric current through the magnetic field generated by the current flowing in a wire.

2. **Evaluating Effectiveness**:
- **Bulb, LED, and CFL**: These devices require a certain amount of current to light up. If the current is too low, they may not provide a clear indication of current flow.
- **Magnetic Compass**: A magnetic compass responds to the magnetic field created by electric current. It can show deflection even with low current, making it sensitive to changes in current flow.

3. **Conclusion**:
- Among all the options, the magnetic compass is the most effective tester for electric current because it can detect even small amounts of current through the magnetic field it senses, while the other options require a minimum threshold of current to function.

### Final Answer:
The best tester for electric current is the **magnetic compass**.

---