Question

3 most early motors used direct current (dc). unfortunately, dc motors frequently spark fires. why? a high temperatures cause wires to melt b rotors rub against a power source and create sparks c strong magnetic fields create high - energy heat waves d loose connections between wires form sparks

Explanation:

To determine why DC motors spark fires, we analyze each option:

• Option A: High temperatures melting wires is more about overheating damage, not the primary cause of sparks in DC motors.
• Option B: Rotors in DC motors have brushes (for commutator) that can rub against the commutator (part of the motor's power - transfer mechanism), creating sparks due to the electrical contact and friction. This is a common cause of sparks in early DC motors.
• Option C: Strong magnetic fields in DC motors are part of their operation, but they don't create "high - energy heat waves" that cause sparks. The magnetic fields are for torque production, not spark generation.
• Option D: Loose connections between wires can cause sparks in electrical systems, but in the context of DC motors, the sparking is more related to the internal motor components (like brushes and commutator) rather than loose wire connections as the primary cause.

Answer:

B. Rotors rub against a power source and create sparks