What determines the rate at which energy is delivered by a current?

Why does the cord of an electric heater not glow while the heating element does?

Will current flow more easily through a thick wire or a thin wire of the same material,when connected to the same source? Why?

Several electric bulbs designed to be used on a $220\, V$ electric supply line,are rated $10\, W$. How many lamps can be connected in parallel with each other across the two wires of a $220\, V$ line if the maximum allowable current is $5\, A$?

Name a device that helps to maintain a potential difference across a conductor.

Explain the following.
$(a)$ Why are copper and aluminium wires usually employed for electricity transmission?