Electronic Science - Online Test
Q1. In the following circuit, X is given by
Answer : Option A
Explaination / Solution:
Q2. A region of negative differential resistance is observed in the current voltage characteristics of a silicon PN junction if
Answer : Option A
Explaination / Solution:
In case of Tunnel diode formed by PN junction, tunnel diode gives negative resistance and works in forward bias, and in tunnel diode both N and P regions are heavily doped.
Q3. In electrolytic capacitors positive terminal is
Answer : Option B
Explaination / Solution:
Aluminium electrolytic capacitors have the Aluminium foil anode (positive terminal) which is etched and covered with a layer of Aluminium Oxide which acts as a dielectric. The whole assembly is covered using a paper separator soaked in electrolyte such as, Borax or Glycol and covered by Aluminium foil which acts as cathode ( negative electrode)
Q4. The graph associated with an electrical network has 7 branches and 5 nodes. The number of independent KCL equations and the number of independent KVL equations, respectively, are
Answer : Option D
Explaination / Solution:
Q5. A potentiometer has a uniform wire of length 10m and resistance 5 ohms. The potentiometer is connected to an external battery of emf of 10V and negligible internal resistance and a resistance of 995 ohms in series. The potential gradient along the wire is:
Answer : Option D
Explaination / Solution:
The total resistance is the sum of the resistance of the potentiometer and the external resistance.
R = Rpot + Rext = 5 + 995 = 1000 ohms .
The current through the potentiometer wire I = E/R = 10/1000 = 0.01A.
The potential drop across the potentiometer wire is
The potential gradient = ( potential drop across the potentiometer wire)/ length of the potentiometer wire)
= 0.05/10
= 5 × 10-3 V/m
= 5 m V/m
Q6. A magnet of magnetic moment is aligned in the direction of magnetic field of 0.1.T. What is the net work done to bring the magnet normal to the magnetic field?
Answer : Option B
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 placed perpendicular to the direction of the field,its potential energy is .Work done in rotating the magnet is equal to the change in its potential energy.
Q7. An iron bar magnet of length 10cm and cross section 1 has a magnetization of . Magnet's pole strength is
Answer : Option A
Explaination / Solution:
No Explaination.
Q8. P-N junction can be used as
Answer : Option A
Explaination / Solution:
The resistance of p-n junction diode becomes low when forward biased and becomes high when reverse biased. Therefore it allows the current to pass through it when it is forward biased and does not allow when reverse biased. Hence it can rectify AC into DC.
Q9. The following binary values were applied to the X and Y inputs of NAND latch
shown in the figure in the sequence indicated below : 
X = ,Y = X = ,Y = X = Y =
The corresponding stable P Q, output will be
Answer : Option C
Explaination / Solution:
No Explaination.
Q10. For the circuit with ideal diodes shown in the figure, the shape of the output (Vout) for the given sine wave input (Vin) will be
Answer : Option C
Explaination / Solution:
For positive half A1, we have
Vout = - Vin
For negative half A2, both diode will be OFF.
So, Vout = 0
Hence, the output is obtained as
