What is resistance ?

What is the resistance of a semiconductor at zero Kelvin?

2 amp current flowing through a wire produces 10 calories ofheat in 20 seconds.What is the resistance of the wire ?

Two lamps need 50V and 2.0amp each in order to operate at a designed brilliancy. They are to be connected in series across a 120 volt line. What is the resistance of the rheostat which must be placed in series with the lamp?