why does a candle appear to go out when a copper coil is placed over the flame?

Combustion requires three things: fuel (wax here), oxygen (air here),
ignition temperature (a match here probably). Remove one and the combustion
stops -- that's the principles firemen use to put out fires. In the case of
your candle the high thermal conductivity of copper probably is conducting
sufficient heat from the flame that the flame goes out, but the heat
capacity of the melted wax, wick, etc. probably "holds" enough heat that the
temperature exceeds the ignition temperature if the copper wire is removed.
If this mechanism is operating you can test it by holding the copper coil
around the flame area for some time, so that the molten wax and wick cool,
the flame will not re-ignite when you remove the copper coil

Source:
http://www.newton.dep.anl.gov/askasci/phy00/phy00529.htm

Well, it sounds like the candle is just a little shy and doesn't want to show off its fiery dance moves in front of the copper coil. It's like when you're at a party and you see someone you're not comfortable dancing in front of, so you just pretend to be extinguished. But don't worry, once the copper coil is removed, the candle will gather up the courage to light up again and continue its hot performance. Just remember, even candles need their time to shine!

When a copper coil is placed over a candle flame, it appears to go out because of two reasons: heat transfer and oxygen access. The high thermal conductivity of copper allows it to rapidly conduct heat away from the flame, lowering the temperature at the combustion site. Since combustion requires a certain ignition temperature to be sustained, once the temperature drops below this threshold, the flame goes out.

Additionally, the copper coil restricts the flow of oxygen to the flame. Oxygen is crucial for combustion, as it reacts with the fuel (wax) to generate heat and sustain the flame. By covering the flame with the copper coil, it impedes the oxygen supply, further contributing to the extinguishing of the flame.

To test this mechanism, you can try holding the copper coil around the flame for an extended period, allowing the molten wax and wick to cool. In this case, the flame will not reignite when the copper coil is removed, indicating that the heat transfer and restricted oxygen access were responsible for the flame going out.

This explanation is based on the principles of combustion and heat transfer. Further insights can be found at the source provided: http://www.newton.dep.anl.gov/askasci/phy00/phy00529.htm

When a copper coil is placed over the flame of a candle, it appears to go out because the copper coil conducts heat from the flame. Combustion requires three things: fuel (wax in this case), oxygen (from the air), and an ignition temperature (provided by a match or lighter). By adding the copper coil, the high thermal conductivity of copper conducts enough heat from the flame that the temperature drops below the ignition temperature, causing the flame to go out.

However, the heat capacity of the melted wax, wick, and other components of the candle holds enough heat that the temperature remains above the ignition temperature even after the flame is extinguished by the copper coil. So, if the copper coil is removed, the heat stored in the melted wax and wick can reignite the flame.

To test this mechanism, you can hold the copper coil around the flame area for some time, allowing the molten wax and wick to cool down. In this case, the flame will not re-ignite when you remove the copper coil.

Source: http://www.newton.dep.anl.gov/askasci/phy00/phy00529.htm