TEST SERIES - 67 (I)

The wire having black plastic covering is a

• Line wire

• Neutral wire

• Earth wire

• None of the above

The wire having a green plastic covering is a

• Line wire

• Neutral wire

• Earth wire

• None of the above

When the hot and cold junctions of a thermocouple are interchanged the thermo-emf

• Becomes zero

• Becomes double

• Remains same

• Changes sign

For electroplating a spoon, it is placed in the voltameter at

• The position of anode

• The position of cathode

• Anywhere in the electrolyte

• None of the above

If the length of a wire is doubled and its cross-section is also doubled, then its resistance will

• Become one fourth

• Become four times

• Become two times

• Remain unchanged

The resistance of a wire is R. It is stretched uniformly so that its length is doubled. The resistance now becomes

• 2R

• R/2

• 4R

• R/4

Which of the following statements is not true?

• Conductance is the reciprocal of resistance and is measured in siemens

• Ohm’s law is not applicable at very low and very high temperature

• Ohm’s law is applicable to semiconductor

• Ohm’s law is not applicable to electron tubes, discharge tubes and electrolytes

A point charge is brought in an electric field. The field at a nearby point

• may increase if the charge is positive

• may decrease if the charge is negative

• Both (a) and (b)

• None of the above

A proton, when accelerated through a potential difference of V volts, has an associated wavelength of l. In order to have the same associated wavelength, an a-particle must be accelerated through a potential difference of

• V volts

• 4V volts

• 2V volts

• V/8 volts

A magnetic field

• Always exerts a force on a charged particle

• Never exerts a force on a charged particle

• Exerts a force on a charged particle if it is moving across the magnetic lines of force

• Never exerts a force on a charged particle if it is moving along the magnetic lines of force