← MES Jr. Grade
Past Questions — 2015
The materials in which valence electrons are bounded very tightly to their parent atoms are called
A)
ferrites
B)
super conductors
C)
insulators
D)
none of these
In insulators, valence electrons are tightly bound to their parent atoms, so they cannot move freely and therefore do not conduct electricity well. Ferrites are magnetic ceramic materials, and superconductors allow current to flow with zero resistance under certain conditions. Hence, the correct answer is insulators.
Line insulators are made of
A)
porcelain
B)
mica
C)
marble
D)
pve
Line insulators used on overhead transmission and distribution lines are commonly made of porcelain because it has high dielectric strength, good mechanical strength, and withstands weathering. Mica is used in electrical insulation applications but not as line insulators. Marble is not used for this purpose. 'pve' is not a standard insulating material for line insulators.
Hali’s effect is used to measure
A)
electric field intensity
B)
magnetic field intensity
C)
carrier concentration
D)
none of these
Hall effect is the development of a transverse voltage across a current-carrying conductor or semiconductor when it is placed in a magnetic field. This Hall voltage is used to measure magnetic field intensity. It is not used to measure electric field intensity directly, and while it can help determine carrier concentration in semiconductors, the standard direct application asked here is magnetic field measurement.
Which one of the following bridges is used for measurement of dielectric loss and power factor of a capacitor?
A)
Maxwell’s bridge
B)
Anderson bridge
C)
De Sautty’s bridge
D)
Schering bridge
The Schering bridge is specifically used to measure the capacitance, dielectric loss, and power factor of a capacitor. Maxwell’s bridge and Anderson bridge are mainly used for inductance measurement, while De Sautty’s bridge is used for comparing capacitances, not for dielectric loss and power factor measurement.
Superconducting metal in superconducting state has relative permeability of
A)
More than one
B)
One
C)
Zero
D)
Negative
A superconductor in the superconducting state exhibits the Meissner effect, meaning it expels magnetic flux from its interior. Hence its magnetic susceptibility is strongly diamagnetic and the relative permeability becomes approximately 0. Therefore, the correct answer is Zero. Option (b) one is for ordinary non-magnetic materials, while (a) and (d) are not correct for superconductors.
The difference between the indicated value and the true value of a quantity is
A)
gross error
B)
absolute error
C)
dynamic error
D)
relative error
The difference between the indicated (measured) value and the true value of a quantity is called the absolute error. Gross error refers to large human mistakes, dynamic error occurs when the instrument cannot follow rapid changes, and relative error is the absolute error divided by the true value.
Fermi level in a p type semiconductor lies close to which one of the following?
A)
The top of the valence band
B)
The bottom of the valence band
C)
The top of the conduction band
D)
The bottom of the conduction band
In a p-type semiconductor, acceptor impurities create more holes, so the Fermi level shifts downward and lies closer to the valence band. Therefore, it is nearest to the top of the valence band. The conduction band options are incorrect because the Fermi level in p-type material moves away from the conduction band.
Which of the following is the most sensitive device?
A)
Thermocouple
B)
RTD
C)
Thermistor
D)
Pyrometer
A thermistor is the most sensitive temperature-sensing device among the given options because its resistance changes very rapidly with temperature. RTDs are accurate and stable but less sensitive than thermistors. Thermocouples have lower sensitivity, and pyrometers are used for non-contact high-temperature measurement, not for highest sensitivity.
To implement the expression ABCD + ABCD + ABCD, it takes one OR gate and
A)
three AND gates and three inverters
B)
three AND gates and four inverters
C)
three AND gates
D)
one AND gates
The expression contains three product terms: ABCD, ABCD, and ABCD. Each product term can be implemented using one AND gate, so a total of three AND gates are needed. Since the question already states one OR gate is used to combine them, no inverters are required as written. Therefore, the correct choice is three AND gates.
If there are four 4-bit registers that need to communicate with a 4-line common bus, the number of 4X1-Multiplexer required is
A)
2
B)
4
C)
8
D)
None of these
A 4-line common bus needs one line for each bit position. Since the registers are 4-bit, there are 4 bit positions to be connected to the bus. For each bit position, one 4×1 multiplexer is required to select one of the four registers’ bits onto that bus line. Therefore, the total number of 4×1 multiplexers needed is 4. Options (a) 2 and (c) 8 are incorrect, and (d) is also incorrect because 4 is listed in option (b).
What is a digital-to-analog converter?
A)
It takes the digital information from an audio CD and converts it to a usable form.
B)
It allows the use of cheaper analog techniques, which are always simpler.
C)
It stores digital data on a hard drive.
D)
It converts direct current to alternating current.
A digital-to-analog converter (DAC) converts digital signals or data into a corresponding analog output. In the given options, (a) describes this process by referring to digital information from an audio CD being converted into a usable analog form such as sound. Option (b) is about analog techniques, not conversion. Option (c) is data storage, and option (d) describes an inverter/AC converter, not a DAC.
In how many ways can 5 balls be chosen so that 2 are red and 3 are black?
A)
910
B)
990
C)
970
D)
960
This is a combinations question. The intended interpretation is that there are 10 red balls and 10 black balls, and we must choose 2 red and 3 black.
Number of ways = C(10,2) × C(10,3) = 45 × 120 = 5400.
However, since the given options do not include 5400, the standard exam-style reading usually implies a different hidden total, and among the provided choices the marked answer is 990. But mathematically, with the information exactly as written, the problem is incomplete because the total number of red and black balls is not specified.
So this question cannot be solved with high certainty from the text alone.
The logical expression y=A+A’B is equivalent to
A)
y=AB
B)
y=A'B
C)
y=A’+B
D)
y=A+B
Use the Boolean identity: A + A’ব = (A + A’)(A + B). Since A + A’ = 1, this becomes 1·(A + B) = A + B. So y = A + B. The other options are not equivalent to the given expression.
The main advantage of flip-flops over transistor circuit is
A)
immunity from noise
B)
low heating
C)
low propagation delay time
D)
high propagation
Flip-flops are bistable digital storage elements and are preferred in digital circuits because they are less affected by small unwanted voltage variations. This gives them good noise immunity. The other options are not the main advantage: flip-flops do not inherently guarantee low heating, and propagation delay is not their primary advantage.
The statement p <> q = (p — q)(q > p) describes
A)
Commutative Law
B)
Implication Laws
C)
Exportation Law
D)
Equivalence
The expression is intended to represent a logical implication/conditional transformation. In discrete mathematics, such statements are grouped under implication laws rather than commutative law, exportation law, or equivalence. Commutative law deals with swapping order in AND/OR, exportation law is a specific rearrangement of nested implications, and equivalence refers to biconditional logic, not this form.
Which logic circuit is the fastest?
A)
DTL
B)
TIL
C)
RTL
D)
All have same speed
TIL (Transistor-Transistor Logic) is the fastest among the given options. It has better switching speed than RTL (Resistor-Transistor Logic) and DTL (Diode-Transistor Logic) because it uses transistors for both logic processing and amplification, resulting in faster operation and better performance. RTL is the slowest, DTL is faster than RTL, and therefore 'All have same speed' is incorrect.
If p = It is raining, q = She will go to college. “It is raining and she will not go to college” will be denoted by
A)
p * ~q
B)
p * q
C)
~(p * q)
D)
~p * q
Let p = "It is raining" and q = "She will go to college". The statement "It is raining and she will not go to college" translates to p AND NOT q, i.e., p * ~q. Option (b) means p and q, option (c) means not (p and q), and option (d) means not p and q, so only (a) matches exactly.
When an unit receives data it responded with another control signal to acknowledge the receipt of the data, this is known as
A)
Strobe
B)
Interrupt
C)
Polling
D)
Handshaking
In computer organization, when a device receives data and sends back a control signal to acknowledge that the data has been received, the process is called handshaking. It is a two-way coordination method used to synchronize data transfer between sender and receiver. Strobe uses a single control signal, interrupt is for alerting the CPU of an event, and polling is checking devices one by one for service.
What is the correct translation of the following statement into mathematical logic? “Some real numbers are rational”
A)
∃x (real(x) v rational(x))
B)
∀x (real(x) → rational(x))
C)
∃x (real(x) ∧ rational(x))
D)
∃x (rational(x) → real(x))
The statement says that there exists at least one number that is both real and rational. In logic, 'some' means existential quantifier (∃), and 'are rational' together with 'real numbers' means the same x must satisfy both predicates, so we use conjunction (∧). Option (a) uses OR, which would mean x is real or rational, not both. Option (b) means all real numbers are rational, which is false. Option (d) is a conditional and does not express that any such number exists.
The number of failed attempts to access memory, stated in the form of fraction is called as
A)
Hit rate
B)
Miss rate
C)
Failure rate
D)
Delay rate
In cache/memory terminology, a successful access is a hit and an unsuccessful access is a miss. The fraction of memory access attempts that fail is therefore called the miss rate. Hit rate is the fraction that succeeds, while failure rate and delay rate are not standard terms for this definition.
Difference between state table and excitation table is
A)
Excitation table has flip-flop inputs
B)
State table has flip-flop inputs
C)
No differences
D)
None of these
A state table shows the present state, input, next state, and output of a sequential circuit. An excitation table, on the other hand, tells what flip-flop input values are required to achieve a desired transition from present state to next state. Therefore, the excitation table contains flip-flop inputs, while the state table does not. Hence, option (a) is correct.
Performance of an algorithm is determined by
A)
Space
B)
Time
C)
Both (a) and (b)
D)
None of these
The performance of an algorithm is generally evaluated using two main measures: time complexity and space complexity. Time tells how fast the algorithm runs, and space tells how much memory it uses. Since both are important in assessing efficiency, the correct answer is both (a) and (b).
How is a J-K flip-flop made to toggle?
A)
J=0, K=0
B)
J=0, K=1
C)
J=1, K=0
D)
J=1, K=1
A J-K flip-flop toggles when both inputs are high. With J = 1 and K = 1, the output changes to the opposite state on each active clock edge. For comparison: J=0, K=0 gives no change; J=0, K=1 resets the flip-flop; J=1, K=0 sets it.
A graph is called a ___ if it is a connected acyclic graph.
A)
Cyclic graph
B)
Regular graph
C)
Tree
D)
Not a graph
A connected graph with no cycles is called a tree. 'Acyclic' means it has no cycles, and 'connected' means every pair of vertices is joined by a path. Hence the correct term is Tree. The other options are incorrect because a cyclic graph has cycles, a regular graph is defined by equal vertex degrees, and 'not a graph' is false.
A function of type f: A → A, where f(x)=x and x is an element of A then, f on A is called
A)
Inverse function
B)
Identity function
C)
Modular function
D)
None of these
A function f: A → A defined by f(x) = x for every x in A maps each element to itself. Such a function is called the identity function. An inverse function reverses another function, and a modular function is unrelated here.