ANS:D - By whom is this mess being created?

No answer description is available. 

ANS:A - True

No answer description is available. Let's discuss.

ANS:C - magnetic fields

Hall effect is used to find the nature of materials. In metals the uesd to find their magnetic field strength. In semiconductors hall effect used to find whether the material is N type or P type & carrier mobile concentration etc.,

ANS:B - pressure on a crystal

Piezo electric effect is the charge that accumulates in certain solid materials (notably crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure. It is derived from the Greek piezo or piezein which means to squeeze or press, and electric or electron.

ANS:A -

ANS:D - one emitter lead and two base leads

The UJT has three terminals: an emitter (E) and two bases (B1 and B2).

ANS:B - forward breakover voltage

SCR's can also be triggered by increasing the forward voltage beyond their rated breakdown voltage (also called as break over voltage) , but again, this does not rapidly switch the entire device into conduction and so may be harmful so this mode of operation is also usually avoided. Also, the actual breakdown voltage may be substantially higher than the rated breakdown voltage, so the exact trigger point will vary from device to device. A uni-junction transistor is commonly used to trigger SCR.

ANS:A - a PNPN thyristor with 3 terminals

PNPN With 3 - Terminals(Anode, Cathode and Gate).

ANS:D - a remote power source

It produce electricity from sunlight and sunlight is available everywhere and it is free of cost.

ANS:A -