The essential requirements of good heating elements are:

1. High specific resistance: Heating elements should have high specific resistance to generate heat effectively. This means that they should have a high resistance per unit length, which allows them to generate a large amount of heat when a current is passed through them.

2. Free from oxidation: Heating elements should be made from materials that are resistant to oxidation at high temperatures. Oxidation can cause the element to corrode or break down over time, reducing its efficiency or causing it to fail altogether.

3. Low-temperature coefficient of resistance: Heating elements should have a low-temperature coefficient of resistance, which means that their resistance should not change significantly with changes in temperature. This helps to ensure that the element maintains a consistent level of heat output regardless of temperature fluctuations.