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

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In the following circuits PN-junction diodes D1D2 and D3 are ideal for the following potential of A and B, the correct increasing order of resistance between A and B will be

(i) – 10 V, – 5V           (ii) – 5V, – 10 V
(iii) – 4V, – 12V

(a) (i) < (ii) < (iii)                       (b) (iii) < (ii) < (i)
(c) (ii) = (iii) < (i)                       (d) (i) = (iii) < (ii)

Subtopic:  Applications of PN junction |
 63%
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The circuit shown in the following figure contains two diode D1 and D2 each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is

1.  Zero 
2.  0.02
3.  0.03 
4.  0.036

Subtopic:  PN junction |
 80%
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The contribution in the total current flowing through a semiconductor due to electrons and holes are 34 and 14 respectively. If the drift velocity of electrons is 52 times that of holes at this temperature, then the ratio of concentration of electrons and holes is
1. 6 : 5                 

2. 5 : 6

3. 3 : 2                 

4. 2 : 3

Subtopic:  Types of Semiconductors |
 66%
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Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the valve of V0 changes by 

(1) 0.2 V                   

(2) 0.4 V

(3) 0.6 V                   

(4) 0.8 V

Subtopic:  PN junction |
 69%
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In the circuit shown in the figure, the maximum output voltage V0 is :

1. 0 V                        2. 5 V
3. 10 V                      4. 52 

Subtopic:  Rectifier |
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In the following circuit, find I1 and I2.

(a) 0, 0
(b) 5 mA, 5 mA
(c) 5 mA, 0
(d) 0, 5 mA

Subtopic:  Applications of PN junction |
 53%
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For the transistor circuit shown below, if β = 100, the voltage drop between emitter and base is 0.7 V, then the value of VCE will be:
                  
1. 10 V
2. 5 V
3. 13 V
4. 0 V

Subtopic:  Applications of Transistor (OLD NCERT) |
 63%
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The following configuration of gate is equivalent to

1. NAND
2. XOR
3. OR
4. None of these

Subtopic:  Logic gates |
 77%
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Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (1) at R, we must have

(1) X = 0, Y = 1

(2) X = 1, Y = 1

(3) X = 1, Y = 0

(4) X = 0, Y = 0

Subtopic:  Logic gates |
 67%
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