Electronic Science | Science | UGC NET Entrance exams Online Objective Test

UGC NET Entrance exams Science # Electronic Science Magnetism and Matter Prepare / Learn

Q1. permeability of a paramagnetic material is expected to decrease with increasing temperature because

A. random thermal motion increases magnetic moment alignment

B. random thermal motion reduces magnetic moment alignment

C. electrons go into forbidden gap

D. electrons stop moving

Answer : Option B
Explaination / Solution:
No Explaination.

UGC NET Entrance exams Science # Electronic Science Electronic Devices Prepare / Learn

Q2. Majority current carriers in N – types are

A. negative ions

B. holes

C. positive ions

D. electrons

Answer : Option D
Explaination / Solution:

The more abundant charge carriers are called majority carriers, which are primarily responsible for current transport in a piece of semiconductor. In n-type semiconductors they are electrons, while in p-type semiconductors they are holes.

UGC NET Entrance exams Science # Electronic Science Digital Circuits Prepare / Learn

Q3. In an 8085 microprocessor, the contents of the Accumulator, after the following instructions are executed will become XRA A MVI B, F0H SUB B

A. 01 H

B. 0F H

C. F0 H

D. 10 H

Answer : Option D
Explaination / Solution:

UGC NET Entrance exams Science # Electronic Science Electronic Devices Prepare / Learn

Q4. A bar of Gallium Arsenide (GaAs) is doped with Silicon such that the Silicon atoms occupy Gallium and Arsenic sites in the GaAs crystal. Which one of the following statement is true?

A. Silicon atoms act as p-type dopants in Arsenic sites and n-type dopants in Gallium sites

B. Silicon atoms act as n-type dopants in Arsenic sites and p-type dopants in Gallium sites

C. Silicon atoms act as p-type dopants in Arsenic as well as Gallium sites

D. Silicon atoms act as n-type dopants in Arsenic as well as Gallium sites

Answer : Option A
Explaination / Solution:

Silicon atoms act as P- type dopants in Arsenic sites and n- type dopants in Gallium sites.

UGC NET Entrance exams Science # Electronic Science Power Electronics Prepare / Learn

Q5. The correct full wave rectifier circuit is

Answer : Option C
Explaination / Solution:

UGC NET Entrance exams Science # Electronic Science Electric Circuits Prepare / Learn

Q6. R_A and R_B are the input resistances of circuits as shown below. The circuits extend infinitely in the direction shown. Which one of the following statements is TRUE?

A. R_A= R_B

B. RA = RB = 0

C. RA < RB

D. RB = RA/(1+RA)

Answer : Option D
Explaination / Solution:

UGC NET Entrance exams Science # Electronic Science Electrostatic Potential and Capacitance Prepare / Learn

Q7. When 2 charged conductors are connected by a wire,

A. there is always loss of energy

B. there will not be any change in energy

C. there is always gain of energy

D. there is loss or gain of energy depending upon the potentials of the

Answer : Option A
Explaination / Solution:

Let the two conductors have capacitances

C_{1}

and

C_{2}

and let their potentials be

V_{1}

and

V_{2}

. Total initial energy of the conductors

U_{i} = \frac{1}{2} C_{1} V_{1}^{2} + \frac{1}{2} C_{2} V_{2}^{2}

. When two charged conductors are connected by a wire, the flow of charge stops when the potentials are equalized. Let V be the common potential and

Q_{1}

and

Q_{2}

be the charges on the conductors after the common potential is attained.

The final energy

UGC NET Entrance exams Science # Electronic Science Current Electricity Prepare / Learn

Q8. 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 current flowing in the potentiometer is:

A. 0.8 A

B. 0.4 A

C. 0.2 A

D. 0.1 A

Answer : Option B
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

$\begin{array}{l} I = \frac{E}{(R + r)} \\ I = \frac{2}{(4 + 1)} \\ I = 0.4 A \end{array}$

UGC NET Entrance exams Science # Electronic Science Moving Charges and Magnetism Prepare / Learn

Q9. In hydrogen atom, the electron is making

6.6 \times 1 0^{15}

rev./sec around the nucleus in an orbit of radius 0.528 Å .The magnetic moment (

A m^{2}

) will be

A. 1×10−27

B. 1×10−23

C. 1×10−15

D. 1×10−10

Answer : Option B
Explaination / Solution:

Magnetic moment of the electron

μ_{l} = I \times A

.The current due to the orbiting electron

. The magnetic moment

UGC NET Entrance exams Science # Electronic Science Magnetism and Matter Prepare / Learn

Q10. If a magnet is suspended over a container of liquid air, it attracts droplets to its poles. The droplets contain only liquid oxygen and no nitrogen because

A. oxygen is ferromagnetic whereas nitrogen is diamagnetic

B. oxygen is diamagnetic whereas nitrogen is paramagnetic

C. oxygen is ferrimagnetic whereas nitrogen is diamagnetic

D. oxygen is paramagnetic whereas nitrogen is diamagnetic

Answer : Option D
Explaination / Solution:
No Explaination.

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