A radio's 5 A fuse keeps blowing, so the owner fits a 20 A fuse instead. What is the danger?
- Excess current could overheat the wiring and start a fire
- The radio's transmitter output power would be reduced
- The larger fuse would blow more quickly than the old one
- The radio's receiver would become less sensitive
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A. Excess current could overheat the wiring and start a fire
The fuse rating is chosen to protect the wiring and the equipment; a larger fuse lets a fault draw far more current than they can carry. The right response is to find out why the fuse is blowing.
Reference: Electrical safety: overcurrent protection
In a 120 V AC power circuit for station equipment, in which conductor should the fuse or circuit breaker be placed?
- The neutral conductor
- The hot conductor
- The ground conductor
- Both neutral and ground
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B. The hot conductor
Protection belongs in the hot lead so that when it opens, the equipment is disconnected from the source of voltage. A fuse in the neutral would leave the circuit live after it blew.
Reference: Electrical safety: overcurrent protection
A power supply has been switched off and unplugged. What can still give a dangerous shock inside it?
- Current stored in its transformer core
- Voltage stored in its rectifier diodes
- Heat stored in its regulator's heat sink
- Charge stored in its filter capacitors
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D. Charge stored in its filter capacitors
Large filter capacitors can hold a lethal charge long after power is removed unless they are discharged. Transformers and diodes do not retain a charge once the power is off.
Reference: Electrical safety: stored charge