For making laser, usually we use _____.

1. 1. Iron
   2. Ruby
   3. Magnesium
   4. Uranium

The device which converts analogue signal to digital signal is called _____.

1. 1. Modem
   2. CPU
   3. Photodiode
   4. Transformer

In Binary system, the figure 361 is written as _____.

1. 1. 10101101
   2. 10110111
   3. 1001101
   4. 101101001

A.C. voltage is _____.

1. 1. Analogue quantity
   2. Chemical quantity
   3. Digital quantity
   4. Mathematical quantity

Radio waves are _____.

1. 1. Head waves
   2. Water waves
   3. Sound waves
   4. Electromagnetic waves

The wave which do not require any medium is _____.

1. 1. Water waves
   2. Electromagnetic waves
   3. Sound wave
   4. Air waves

A semi-conductor is also used as _____.

1. 1. Rectified
   2. Capacitor
   3. Electronic motor
   4. Transformer

Lightning is formed when_____.

1. 1. Water vapor pro0duces electricity in the clouds
   2. Clouds strike against impurities in air and the friction burns up these impurities
   3. strong opposite charges in different clouds breakdown the resistance offered by the intervening air
   4. Similar charges of electricity rush towards each other and then get repelled

A remote control gadget (for TV etc.) has in it_____.

1. 1. A small transmitter that emits infrared signals
   2. A small electromagnet, that emits electromagnetic
   3. A small oscillator that emits electric pulses
   4. None of these

Though the temperature inside lighted electric bulb is around 2700°C, the filament does not burn because _____.

1. 1. It does not burn in closed system
   2. The oxygen necessary for combustion (and burning) is not available as the bulb is evacuated and filled with pure nitrogen or inert gases
   3. The metal of which it is made is resistant to burning
   4. It is made of non-metallic substance