Final answer:
Excessive current can overheat a motor, potentially causing damage or failure, and safety devices like fuses and circuit breakers are designed to interrupt excessive current to protect mechanisms and prevent accidents.
Step-by-step explanation:
When the current to a motor reaches levels that may cause damage, safety measures are necessary to prevent overheating and potential harm. Motors often draw more current at start-up, which can be intensified under mechanical load, such as when an electric wheelchair ascends a hill, causing the motor to slow and draw more current. This increased current can lead to overheating due to the resistive power in the coil (P = I²R). Overheating or overloading can damage the motor and electrical wires, potentially leading to fires or burns. To prevent such occurrences, devices like fuses and circuit breakers are designed to interrupt the power supply if excessive currents occur, protecting both the motor and the circuitry. It's also relevant to be aware of the physiological impacts of electric current, as currents exceeding 5 mA can cause health issues, including the potentially lethal 'can't let go' effect, where muscles might contract uncontrollably due to electrical shock.