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Examoogle • User • info@examoogle.com • EE-2024-8821
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Minimum arcing voltage will be least in case of
Silver
Graphite
Carbon
Tungsten
Silver
Quick Summary: Silver possesses the lowest minimum arcing voltage among common contact materials because of its superior electrical and thermal conductivity. In electrical switchgear, contacts with low arcing voltage help minimize heat dissipation and erosion during the interruption process.
Silver possesses the lowest minimum arcing voltage among common contact materials because of its superior electrical and thermal conductivity. In electrical switchgear, contacts with low arcing voltage help minimize heat dissipation and erosion during the interruption process.
Vmin≈Φw
Varc∝σ1
The minimum arcing voltage is the threshold potential difference required to maintain a metallic arc between separating contacts. Materials like Silver have low ionization potentials and high thermal conductivity, which allows the heat generated at the contact surface to dissipate quickly, thereby suppressing the formation of an arc plasma and reducing the minimum voltage required to sustain it.
Silver has the highest electrical conductivity of all metals (approx 6.3 × 10°7 S/m).
High conductivity ensures rapid heat dissipation, preventing local melting and stable arc formation.
Tungsten has a much higher arcing voltage, making it suitable for high-energy arc resistance but poorer for low-resistance connections.
Switchgear contacts often use Silver-Cadmium Oxide or Silver-Graphite composites to balance conductivity with wear resistance.
Minimizes contact erosion
Reduces heat accumulation during switching
Lower contact resistance
Silver is susceptible to sulfide tarnishing
Prone to contact welding under high short-circuit currents without additives
Circuit breakers
Relay contacts
High-precision switches
| Feature | Silver | Tungsten |
|---|---|---|
Conductivity | Very High | Low/Moderate |
Melting Point | Moderate (~961°C) | Very High (~3422°C) |
The arcing voltage is closely related to the work function of the material and its ability to emit electrons.
Option B (Graphite) and C (Carbon) generally exhibit higher contact resistance compared to Silver, leading to higher heat generation at the interface.
Tungsten is often used where high melting points are needed to prevent welding, not for low arcing voltage.
A is correct — Silver exhibits the least minimum arcing voltage due to its exceptional electrical conductivity and thermal properties.
Always remember that for contact materials, there is a trade-off: Silver provides excellent conductivity (low arc voltage), while Tungsten provides excellent heat resistance (prevents contact welding).