Electric Resistance Heating

 INDIRECT HEATING 

Resistance heating generates heat by passing electric current through a conductor based on Joule’s Law (

). Direct resistance heating passes current directly through the charge for rapid, efficient heating (e.g., salt baths, rivets). Indirect resistance heating passes current through a high-resistance element, transferring heat via radiation/convection (e.g., ovens,)

Indirect Resistance Heating

Mechanism: Electric current flows through a high-resistance element (like Nichrome), which heats up. This heat is then transferred to the charge via radiation, convection, or conduction.

Key Characteristics: Allows for high, uniform temperature control, easy automation, and can heat non-conductive materials.

Applications: Domestic water heaters, electric kettles, ovens, toasters, and industrial furnaces.

Limitations: Lower overall efficiency compared to direct methods due to heat loss between the element and the charge. 

DIRECT HEATING 

Direct Resistance Heating

Mechanism: The material to be heated (charge) acts as the resistance element itself. Current passes directly through it.

Key Characteristics: Very high efficiency, rapid, and uniform heating, often resulting in automatic stirring.

Applications: Electrode boilers, salt bath furnaces, rivets, and resistance welding.

Limitations: Requires conductive material; harder to control temperature