Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is
A
0.75 A
B
zero
C
0.25 A
D
0.5 A
Explanation
Here D1 is in forward bias and D2 is in
reverse bias so, D1 will conduct and D2 will not
conduct.
So, the current supplied by the battery is
I = $${5 \over {10}}$$ = 0.5 A
2
AIPMT 2011 Mains
MCQ (Single Correct Answer)
Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 $$ \times $$ 1016 m$$-$$3. Doping by indium increases nh to 4.5 $$ \times $$ 1022 m$$-$$3. The doped semiconductor is of
A
p-type having electron concentration ne = 5 $$ \times $$ 109 m$$-$$3
B
n-type with electron concentration ne = 5 $$ \times $$ 1022 m$$-$$3
C
p-type with electron concentration ne = 2.5 $$ \times $$ 1010 m$$-$$3
D
n-type with electron concentration ne = 2.5 $$ \times $$ 1023 m$$-$$3
Explanation
(ni)2
= ne × nh
(1.5 × 1016)2
= ne (4.5 × 1022)
So ne = 5 × 109
Now nh = 4.5 × 1022
$$ \Rightarrow $$ nh $$ >> $$ ne
Hence, semiconductor is p-type
and ne = 5 × 109 m–3
3
AIPMT 2011 Mains
MCQ (Single Correct Answer)
In the following figure, the diodes which are forward biased, are
A
(A), (B) and (D)
B
(C) only
C
(C) and (A)
D
(B) and (D)
Explanation
p-n junction is said to be forward biased
when p side is at high potential than n side. It is for
circuit (A) and (C).
4
AIPMT 2011 Prelims
MCQ (Single Correct Answer)
In forward biasing of the p-n junction
A
the positive terminal of the battery is connected to p-side and the depletion region becomes thick.
B
the positive terminal of the battery is connected to n-side and the depletion region becomes thin.
C
the positive terminal of the battery is connected to n-side and the depletion region becomes thick.
D
the positive terminal of the battery is connected to p-side and the depletion region becomes thin.
Explanation
In forward biasing, the positive terminal of
the battery is connected to p-side and the negative
terminal to n-side of p-n junction. The forward bias
voltage opposes the potential barrier. Due to it, the
depletion region becomes thin.
Questions Asked from Semiconductor Electronics
On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
