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1

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)
For a transistor $$\alpha$$ and $$\beta$$ are given as $$\alpha = {{{I_C}} \over {{I_E}}}$$ and $$\beta = {{{I_C}} \over {{I_B}}}$$. Then the correct relation between $$\alpha$$ and $$\beta$$ will be :
A
$$\alpha = {{1 - \beta } \over \beta }$$
B
$$\beta = {\alpha \over {1 - \alpha }}$$
C
$$\alpha \beta = 1$$
D
$$\alpha = {\beta \over {1 - \beta }}$$

Explanation

$$\alpha = {{{I_C}} \over {{I_E}}}$$, $$\beta = {{{I_C}} \over {{I_B}}}$$; $${I_E} = {I_C} + {I_B}$$

$$\alpha = {{{I_C}} \over {{I_C} + {I_B}}} = {{{I_C}/{I_B}} \over {{{{I_C}} \over {{I_B}}} + 1}} = {\beta \over {\beta + 1}}$$

$$1 + {1 \over \beta } = {1 \over \alpha }$$

$${1 \over \beta } = {{1 - \alpha } \over \alpha }$$

$$\beta = {\alpha \over {1 - \alpha }}$$
2

JEE Main 2021 (Online) 27th August Morning Shift

MCQ (Single Correct Answer)
For a transistor in CE mode to be used as an amplifier, it must be operated in :
A
Both cut-off and Saturation
B
Saturation region only
C
Cut-off region only
D
The active region only

Explanation

Active region of the CE transistor is linear region and is best suited for its use as an amplifier.
3

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)
Four NOR gates are connected as shown in figure. The truth table for the given figure is :

A
B
C
D

Explanation



$$y = \overline {(\overline {A + \overline {A + B} } ) + (\overline {B + \overline {A + B} } )} $$

$$y = (A + \overline {A + B} ).(B + \overline {A + B} )$$

A B y
0 0 1
0 1 0
1 0 0
1 1 1
4

JEE Main 2021 (Online) 26th August Morning Shift

MCQ (Single Correct Answer)
Statement I : By doping silicon semiconductor with pentavalent material, the electrons density increases.

Statement II : The n-type semiconductor has net negative charge.

In the light of the above statements, choose the most appropriate answer from the options given below :
A
Statement - I is true but Statement - II is false.
B
Statement - I is false but Statement - II is true.
C
Both Statement I and Statement II are true.
D
Both Statement I and Statement II are false.

Explanation

Pentavalent activities have excess free e$$-$$, so e$$-$$ density increases but overall semiconductor is neutral.

Questions Asked from Electronic Devices

On those following papers in MCQ (Single Correct Answer)
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JEE Main 2021 (Online) 1st September Evening Shift (1)
JEE Main 2021 (Online) 31st August Evening Shift (1)
JEE Main 2021 (Online) 31st August Morning Shift (2)
JEE Main 2021 (Online) 27th August Evening Shift (1)
JEE Main 2021 (Online) 27th August Morning Shift (1)
JEE Main 2021 (Online) 26th August Evening Shift (1)
JEE Main 2021 (Online) 26th August Morning Shift (2)
JEE Main 2021 (Online) 27th July Evening Shift (1)
JEE Main 2021 (Online) 25th July Morning Shift (1)
JEE Main 2021 (Online) 22th July Evening Shift (1)
JEE Main 2021 (Online) 20th July Morning Shift (1)
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JEE Main 2021 (Online) 26th February Evening Shift (1)
JEE Main 2021 (Online) 26th February Morning Shift (1)
JEE Main 2021 (Online) 25th February Evening Shift (2)
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JEE Main 2020 (Online) 6th September Morning Slot (1)
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