Electronic Science - Online Test
Q1. Consider the oscillator circuit shown in the figure. The function of the network (shown in
dotted lines) consisting of the
100kΩ resistor in series with the two diodes connected back-toback
is to:
Answer : Option A
Explaination / Solution:
When the output voltage is positive the diode D1 is turned on making 100kΩ resistor to become parallel to 22.1kΩ. So the gain is reduced. When the output voltage becomes negative the diode D2 is turned on thereby again 100kΩ resistor to become parallel to 22.1kΩ. So the gain is reduced. With the use of diodes, the non ideal OP-Amp is made stable to produce steady
Q2. The Miller effect in the context of a Common Emitter amplifier explains
Answer : Option D
Explaination / Solution:
Miller effect increase input capacitance, so that there will be decrease in gain in the high frequency cutoff frequency.
Q3. The Boolean function Y = AB + CD is to be realized using only 2 - input NAND gates. The minimum number of gates required is
Answer : Option B
Explaination / Solution:
This is SOP form and we require only 3 NAND gate
Q4. The Boolean expression 
can be
minimized to
can be
minimized to
Answer : Option D
Explaination / Solution:
Q5. An electrolytic capacitor is marked 8 μF, 220 V. It can be used in a circuit where the p.d. across the capacitor may be
Answer : Option D
Explaination / Solution:
The break down potential of the capacitor is 220 V. In order to prevent damage to a capacitor, it should be always used in a circuit where the p.d is less than its break down potential. The p.d difference can only be 200 V.
Q6. A parallel plate capacitor filled with two dielectrics is shown in the figure below. If the electric field in the region A is 4 kV/cm, the electric field in the region B, in kV/cm, is
Answer : Option C
Explaination / Solution:
Q7. The wire of the potentiometer has resistance 4 ohms and length 1 m. It is connected to a cell of e.m.f. 2 volts and internal resistance 1 ohm, the potential gradient in the potentiometer wire is:
Answer : Option D
Explaination / Solution:
If the battery has an e.m.f E, resitance of the potentiometer is R and the internal resistance of the battery is r, then the current I flowing in the potentiometer wire is given as,
The potential difference V across the potentiometer,
The potential gradient = ( potential drop across the potentiometer)/ length of the potentiometer wire)
= V/l
= 1.6/1
Potential gradient = 1.6 V/m
Q8. If number of turns, area and current through a coil is given by n, A and i respectively then its magnetic moment will be
Answer : Option D
Explaination / Solution:
The magnetic moment associated with a coil carrying current is given by the product of its area and the current through it. M=n I A
Q9. Correct unit of Bohr magneton is
Answer : Option B
Explaination / Solution:
No Explaination.
Q10. Electrons are forbidden in a band (in a crystal) called the
Answer : Option A
Explaination / Solution:
A region of values of energy that electrons in an ideal crystal (without defects) cannot have. In semiconductors the forbidden band separating the valence band and the conduction band is usually considered. In this case the energy difference between the lower level (bottom) of the conduction band and the upper level (ceiling) of the valence band is called the width of the forbidden band.
