Electronic Science - Online Test
Q1. 
In the silicon BJT circuit shown below, assume that the emitter area of transistor Q1 is half that of transistor Q2
The value of current I0 is approximately
Answer : Option B
Explaination / Solution:
Since, emitter area of transistor Q1 is half of transistor Q2, so current
Q2. When Ge crystal is doped with phosphorus atoms, it becomes
Answer : Option A
Explaination / Solution:
Doping is the process of intentionally introducing impurities into an extremely pure (i.e., intrinsic) semiconductor in order to change its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic semiconductor. A semiconductor which is doped to such high levels that it acts more like a conductor than a semiconductor is called degenerate.
Dopant atoms can either be “donors” or “acceptors.” Donors increase the elctron concentration in the silicon, whereas acceptors increase the hole concentration.
When Germanium crystal is doped with phosphorus atoms, then it becomes N-type.
Q3. The transistor circuit shown uses a silicon transistor with VBE = 0.7V, IC ≈ IE and a dc current
gain of 100. The value of V0 is
Answer : Option A
Explaination / Solution:
No Explaination.
Q4. 
Consider the common emitter amplifier shown below with the following circuit parameters:
The resistance seen by the source vs is
Answer : Option B
Explaination / Solution:
Q5. 
Assuming an ideal transformer,. The Thevenin’s equivalent voltage and impedance as seen from the terminals x and y for the circuit in figure are
Answer : Option A
Explaination / Solution:
Q6. A parallel plate condenser is immersed in an oil of dielectric constant 2. The field between the plates is
Answer : Option C
Explaination / Solution:
In the presence of a dielectric with K=2, the electric field =E/K= E/2, The force also reduces by 1/2
Q7. The magnetic field in a circular loop of diameter 0.1 m carrying a current of 1 A is
Answer : Option C
Explaination / Solution:
Q8. Resistance of a conductor is
Answer : Option B
Explaination / Solution:
According to Ohm’s law, V=I R. Therefore R=V/I
Q9. the magnetic needle has magnetic moment d moment of inertia . It performs 10 complete oscillations in 6.70 s. Magnitude of the magnetic field is
Answer : Option D
Explaination / Solution:
No Explaination.
Q10. 
The amplifier circuit shown below uses a silicon transistor. The capacitors Cc and CE can be assumed to be short at signal frequency and effect of output resistance r0 can be ignored. If CE is disconnected from the circuit, which one of the following statements is true
Answer : Option A
Explaination / Solution:
The equivalent circuit of given amplifier circuit (when CE is connected, RE is short-circuited)
