The correct answer is: C. Both mechanical noise and arc between contacts.
When a lamp is switched on, the current flowing through the filament causes it to heat up and emit light. When the lamp is switched off, the current stops flowing and the filament cools down. This rapid change in temperature causes the filament to contract and expand, which produces a mechanical noise.
In addition, the switching operation can also produce an arc between the contacts of the switch. This arc is a high-energy discharge of electricity that can cause interference with radio signals.
The mechanical noise and the arc between the contacts can both be picked up by the radio, which is why you may hear a noise when you switch a lamp on or off.
Here is a more detailed explanation of each option:
- Option A: Arcs across separating contacts. This is the correct answer. When a lamp is switched on, the current flowing through the filament causes it to heat up and emit light. When the lamp is switched off, the current stops flowing and the filament cools down. This rapid change in temperature causes the filament to contract and expand, which produces a mechanical noise. In addition, the switching operation can also produce an arc between the contacts of the switch. This arc is a high-energy discharge of electricity that can cause interference with radio signals.
- Option B: Mechanical noise of high intensity. This is not the correct answer. The mechanical noise produced by the switching operation is not of high intensity. It is a low-pitched, crackling sound that is easily drowned out by other noises.
- Option C: Both mechanical noise and arc between contacts. This is the correct answer. The mechanical noise and the arc between the contacts can both be picked up by the radio, which is why you may hear a noise when you switch a lamp on or off.
- Option D: None of the above. This is not the correct answer. The switching operation does produce noise, which can be picked up by the radio.