Physics M.C.Q (1 Marks)

Which is reverse biased diode

Which one is in forward bias

P-type semiconductor is formed when
A. As impurity is mixed in Si                                                                         B. Al impurity is mixed in Si
C. B impurity is mixed in Ge                                                                         D. P impurity is mixed in Ge(a) A and C(b) A and D(c) B and C(d) B and D

The symbol given in figure represents

Assertion  :  NOT gate is also called inverter circuit.
Reason      : NOT gate inverts the input order.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :  Zener diode works on a principle of breakdown voltage.
Reason      : Current increases suddenly after breakdown voltage.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion : V-i characteristic of P-N junction diode is same as that of any other conductor.
Reason     : P-N junction diode behave as conductor at room temperature.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   At 0 K Germanium is a superconductor. 
Reason    :    At 0 K Germanium offers zero resistance.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :  NAND or NOR gates are called digital building blocks.
Reason      : The repeated use of NAND (or NOR) gates can produce all the basic or complicated gates.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :  A transistor is a voltage-operating device.
Reason     : Base current is greater than the collector current.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :  In transistor common emitter mode as an amplifier is preferred over common base mode.
Reason     : In common emitter mode the input signal is connected in series with the voltage applied to the base emitter function.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :  Two P-N junction diodes placed back to back, will work as a NPN transistor.
Reason     : The P-region of two PN junction diodes back to back will form the base of NPN transistor.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :   Semiconductors do not Obey's Ohm's law. 
Reason     : Current is determined by the rate of flow of charge carriers.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If assertion is false but reason is true.

Assertion :   We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals.
Reason     : The current through the PN junction is not same in forward and reversed bias.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If assertion is false but reason is true.

Assertion  :   Silicon is preferred over germanium for making semiconductor devices.
Reason      : The energy gap for germanium is more than the energy gap of silicon.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  : If the temperature of a semiconductor is increased then it's resistance decreases.
Reason      : The energy gap between conduction band and valence band is very small(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   Base in a transistor is made very thin as compared to collector and emitter regions.                
Reason     : Due to thin base power gain and voltage gain is obtained by a transistor.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion : The resistivity of a semiconductor increases with temperature.
Reason     : The atoms of a semiconductor vibrate with larger amplitude at higher temperature there by increasing it's resistivity.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :  A transistor amplifier in common emitter configuration has a low input impedence.
Reason      : The base to emitter region is forward biased.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion : In a common emitter transistor amplifier the input current is much less than the output current.
Reason     : The common emitter transistor amplifier has very high input impedance.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Amplification factor of a triode is 10. When the plate potential is 200 volt and grid potential is – 4 volt, then the plate current of 4mA is observed. If plate potential is changed to 160 volt and grid potential is kept at – 7 volt, then the plate current will be(a) 1.69 mA(b) 3.95 mA(c) 2.87 mA(d) 7.02 mA

A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be(a) 1 kW  (b) 5 kW(c) 10 kW(d) 20 kW

A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current(a) 6.25 V(b) 0.16 V(c) 15.2 V(d) None of these

A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be(a) 1 mA(b) 2 mA(c) 4 mA(d) None of these

In a negative logic the following wave form corresponds to the

The combination of gates shown below produces

The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is(a) 10.6 Å(b) 0.53 Å(c) 21.2 Å                                           (d) None of these

A transistor is used as an amplifier in CB mode with a load resistance of 5 k W the current gain of amplifier is 0.98 and the input resistance is 70 W, the voltage gain and power gain respectively are(a) 70, 68.6(b) 80, 75.6(c) 60, 66.6(d) 90, 96.6