Electrical Materials Set 2

The amplitude of vibration of the atoms varies with temperature ✘ The electron density varies with temperature ✘ The electron gas density varies with temperature ✘ None of the above ✔

Speed of the machine ✘ Contact pressure ✘ Surface conditions of brush and commutator ✘ All of the above ✔

Insulators ✘ Conductors ✘ Semiconductors ✘ Superconductors ✔

Diamond ✘ High speed steel ✘ Mild steel ✘ Cast iron ✔

Insulator ✘ Metal ✘ Intrinsic semiconductor ✘ None of the above ✔

Positive ions only ✘ Negative ions only ✘ Positive and negative ions ✘ Electrons and holes ✔

Intensity ✘ Speed ✘ Frequency ✘ Wave length ✔

oth have great tendency for oxidation ✘ Both have low melting point ✘ Very large length of wires will be required ✘ All of the above ✔

Silica ✘ Germanium ✘ Selenium ✘ Gallium arsenide ✔

Carbon crystals ✘ Solid carbon granules ✘ Pulverized coal ✘ Finely divided carbon black ✔