*Question T0A11:
What hazard exists in a power supply immediately after turning it off?*  

*Correct Answer is  D: Charge stored in filter capacitors*  

### AI Response: (may contain errors)  

The correct answer to the question about hazards in a power supply immediately after turning it off is:

**D: Charge stored in filter capacitors**

### Explanation of the Correct Answer:
- **Charge stored in filter capacitors**: After a power supply is turned off, the filter capacitors can still hold a significant amount of charge. This stored charge can pose a serious shock hazard if someone comes into contact with the terminals of the capacitors. It's important to discharge these capacitors safely before working on the power supply.

### Why the Other Choices are Incorrect:
- **A: Circulating currents in the dc filter**: Circulating currents typically occur in a circuit when there are multiple paths for current to flow, often due to improper grounding or connections. This is not a primary concern immediately after turning off a power supply.

- **B: Leakage flux in the power transformer**: Leakage flux refers to the magnetic field that does not contribute to the energy transfer in a transformer. While it can be a concern during operation, it does not pose a hazard immediately after the power supply is turned off.

- **C: Voltage transients from kickback diodes**: Kickback diodes are used to protect circuits from voltage spikes when inductive loads are switched off. While they can generate transients during operation, they are not a concern immediately after the power supply is turned off.

### Useful Rules of Thumb:
- Always assume that capacitors can hold a charge even after power is removed.
- Use a resistor to safely discharge capacitors before working on electronic equipment.
- Wait a sufficient amount of time after turning off the power supply to allow capacitors to discharge, or use a multimeter to check for residual voltage.

By understanding these concepts, you can ensure safety when working with power supplies and their components.