Physics : Semiconductor Electronics: Materials, Devices and Simple Circuits

A laser beam is used for carrying out surgery because it

• is highly monochromatic

• is highly coherent

• is highly directional

• can be sharply focused

To a germanium sample, traces of gallium are added as an impurity. The resultant  sample would behave like

• a conductor

• a p-type semiconductor

• an n-type semiconductor

• an insulator

In the following common emitter configuration an npn transistor with current gain β = 100  is  used. The output voltage of the amplifier will be

• 10 mV

• 0.1 mV

• 1.0 mV

• 10 V

Assertion: The resistivity of a semiconductor increases with temperature. 

Reason:  The atoms of a semiconductor vibrate with larger amplitude at higher temperatures thereby increasing its resistivity.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion: The possibility of an electric bulb fusing is higher at the time of switching on and off.

Reason: Inductive effects produce a surge at the time of switch-off and switch-on.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

At 0 K temperature, a p-type semiconductor

• does not have any charge carriers

• has few holes but no free electrons

• has few holes and few free electrons 

• has equal number of holes and free electrons

The potential barrier, in the depletion layer, is due to 

• ions

• electrons

• holes

• forbidden band

Assertion:  LASER is used to measure distant object as moon. 

Reason: They are highly coherent source of light.

• If both assertion and reason are true but reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Assertion: During reverse biasing a diode doesn't conduct current. 

Reason: It narrows the depletion layer.

• If assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion andreason are true and reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Assertion:  Electric appliances with metallic body e.g., heaters, presses etc., have three pin connections, whereas an electric bulb has a two pin connection. 

Reason:  Three pin connections reduce heating of connecting cables.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are  true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion is false but reason is true.