Electronic Science - Online Test
Q1. An n+ - n Silicon device is fabricated with uniform and non-degenerate donor doping concentrations of ND1 = 1 × 1018
cm-3 and ND2 = 1 × 1015
cm-3 corresponding to the n+ and n regions respectively. At the operational temperature T, assume complete impurity ionization, kT/q = 25 mV, and intrinsic carrier concentration to be ni = 1 × 1010 cm-3, What is the magnitude of the built-in potential of this device?
Answer : Option D
Explaination / Solution:
Q2. In the circuit shown below the op-amps are ideal. Then, Vout in Volts is
Answer : Option C
Explaination / Solution:
No Explaination.
Q3. The circuit diagram of a standard TTL NOT gate is shown in the figure. Vi = 25 V, the modes of operation of the transistors will be
Answer : Option B
Explaination / Solution:
No Explaination.
Q4. The action of the dielectric to increase the capacitance is due to
Answer : Option D
Explaination / Solution:
When a dielectric is placed between the plates of a capacitor, electric polarization results in a reverse electric field inside the dielectric.
The net electric field reduces and therefore the potential reduces. Sincethe capacitance increases because the potential reduces.The charges in a dielectric are incapable of moving since all dielectrics are essentially insulators. The molecules of the dielectric acquire an induced dipole moment in the direction of the applied field, due to rearrangement of their electron clouds.The charges in the dielectric and those on the capacitor plates are not equal in magnitude. They are not neutralized. The dipoles in the dielectric are oriented perpendicular to the plates as the electric field is perpendicular to the plates.
The net electric field reduces and therefore the potential reduces. Sincethe capacitance increases because the potential reduces.The charges in a dielectric are incapable of moving since all dielectrics are essentially insulators. The molecules of the dielectric acquire an induced dipole moment in the direction of the applied field, due to rearrangement of their electron clouds.The charges in the dielectric and those on the capacitor plates are not equal in magnitude. They are not neutralized. The dipoles in the dielectric are oriented perpendicular to the plates as the electric field is perpendicular to the plates.
Q5. In the circuit shown below, the voltage and current sources are ideal. The voltage (Vout) across the
current source, in volts, is
Answer : Option D
Explaination / Solution:
Q6. 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, if a cell of e.m.f. 1.2 volt is balanced by it, the balancing length will be
Answer : Option D
Explaination / Solution:
If the battery has 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 by,
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
The emf of the cell
Q7. The work done in rotating a magnet of magnetic moment in a magnetic field of T form the direction along the magnetic field to opposite direction to the magnetic field, is
Answer : Option A
Explaination / Solution:
The potential energy of a magnetic dipole of moment m placed in a magnetic field is When the magnet is aligned in the direction of the field, and the initial potential energy When the magnet is aligned opposite to the direction of the fieldits potential energy isWork done in rotating the magnet is equal to the change in its potential energy.
Q8. Diamagnetic susceptibilities are very nearly temperature independent because
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. The behavior of Ge as a semi – conductor is due to the width of
Answer : Option B
Explaination / Solution:
No Explaination.
Q10. A good transconductance amplifier should have
Answer : Option C
Explaination / Solution:
A good trans conductance amplifier should have high input and output resistance.
