If the efficiency of a machine is to be high, what should be low?

Resistance of a material always decreases if

A. Temperature of material is decreased

B. Temperature of material is increased

C. Number of free electrons available becomes more

D. None of the above is correct

The rating of a fuse wire is always expressed in

A. Ampere-hours

B. Ampere-volts

C. kWh

D. Amperes

The minimum charge on an ion is

A. Equal to the atomic number of the atom

B. Equal to the charge of an electron

C. Equal to the charge of the number of electrons in an atom

D. Zero

Current velocity through a copper conductor is

A. the same as propagation velocity of electric energy

B. independent of current strength

C. of the order of a few micro m/s

D. nearly 3 x 10⁸ m/s