RRB JE (Railways Junior Engineer) CBT EC Test 1 Free Online Test 2026

We know, μ = tan i_p
Where i_p = Polarization or Brewster’s angle
∴ i_p = tan^-1 μ = tan-1(1.732) = 60°

An Op-Amp should have
i) High Bandwidth
ii) High input impedance
iii) Low output impedance
iv) High Gain
v) High CMRR
vi) High slew rate

• Residual resistivity is the resistivity of material at 0 kelvin
• It depends on the imperfections in the lattice
• It is independent of temperature

• Nitrogen is the most electronegative among Arsenic, Nitrogen and Phosphorus.
• As per the periodic table, Nitrogen has an atomic number of 7 and hence its electron configuration is 1s² 2s² 2p³.
• Amongst all the others nitrogen has the highest tendency to attract a shared pair of electrons towards itself.

Truth Table of NAND gate is shown

If one of the inputs is ‘1’ then the output is an inversion of other input.
The NAND based latch truth table is shown

The output will retain its previous state.

The output error voltage of the phase detector is proportional to the phase difference between the reference frequency and VCO signal

Proof:
Let the reference signal be = A_ccos(ωt+θ)
And VCO signal be = A_Vsin(ωt+ϕ)A
The phase detector is a multiplier circuit followed by LPF
Thus, the output of the multiplier is

Let the case and junction temperature be T₁ and T₂. The thermal resistance θ_R = 1^∘C/W. Then power dissipated P_D is given by,

Thus, the case temperature should be, T₁ = 100^∘C

8257 : DMA Controller
8255 : PPI (Programmable Peripheral Interface)
8251 : USART (Universal Synchronous and Asynchronous Receiver Transmitter)
8259 : PIC(Programmable Interrupt Controller)
8253, 8254 : Programmable Timers

Rectifier instrument has the highest frequency range with accuracy within reasonable limits. These instruments are nothing but permanent magnet moving coil instruments used in conjunction with rectifying device for AC measurements (current and voltage) from about 20 Hz to 20 kHz.

The gates required to build a half adder are EX-OR gate and AND gate.

The programming language, scanf is the short form of scan formatted. It is a keyword used as a control parameter meant for reading a string. The string is picked up from the standard input device itself.

The Man Booker Prize for Fiction is a literary prize awarded each year for the best original novel written in the English language and published in the UK.

For Half wave rectifier, Efficiency 
For Full wave rectifier, Efficiency 

The strength of an electromagnet can be increased by introducing a soft iron core inside the coil. We can make the electromagnet stronger by adding more turns to the coil.

For sustained oscillations in an oscillator, there are two conditions that are required to be met:

1. Loop gain Aβ = 1
2. Positive feedback

In the case of positive feedback, the phase difference between input and feedback is 0° or 360°.

The characteristic impedance of a wave travelling in a lossy medium is given by

Put σ = 0 (free space and lossless medium)

• The quantum number defines an electron completely in an atom. 
• There are four types of quantum number - Principal Quantum Number, Azimuthal Quantum Number, Magnetic Quantum Number and Spin Quantum Number. 
• Principal Quantum Number describes the size, shape and energy of the shell to which an electron belongs whereas Azimuthal Quantum Number determines the shape of the electron cloud and the number of sub-shells in a shell. 
• Magnetic Quantum Number determines the orientation of sub-shells whereas the spin quantum number represents the direction of the electron spin. 

A database schema is the skeleton structure that represents the logical view of the entire database. SQL commands can be used to create a database schema.

SQL commands are divided into four subgroups, DDL, DML, DCL, and TCL.

DDL (Data Definition Language) statements are used for creating and defining the Database Schema.

Examples: CREATE, ALTER, DROP statements

While DML (Data Manipulation Language) statements are used for managing data within the Database.

Examples: SELECT, UPDATE, INSERT statements

DCL (Data Control Language) which includes commands that are mostly concerned with rights, permissions and other controls of the database system.

Example: GRANT, REVOKE

TCL (Transaction Control Language) deals with a transaction within a database.

Example: COMMIT, ROLLBACK

Greenhouse effect

• It occurs due to the increase in the percentage of carbon dioxide in the atmosphere
• It absorbs the solar rays and energy of the sun due to which the temperature on the earth increases and natures balance gets disturbed
• Our vehicles and industries are continuously increasing the amount of carbon dioxide in the atmosphere

Global Warming

• Increase in average temperature of the earth surface due to the greenhouse effect is called global warming
• It also refers to the increase in average temperature of the air and sea at earth's surface

Green House Gases (GHG):
The major greenhouse gases are

• Water vapour - causes about 36% - 70% of the greenhouse effect
• Carbon dioxide (CO₂) which causes 9 - 26%
• Methane (CH₄) causes 4 - 9% and ozone (O₃)

So Ethane is not a greenhouse gas

Web browser: A browser is a software application used to locate, retrieve and display content of Web pages, images, video and other files. The browser contacts the Web server and requests information and Web server sends the information back to the Web browser which displays the results on the computer.

Some commonly used web browsers are:

• Internet Explorer: Internet Explorer (IE) is a web browser from Microsoft
• Firefox: Firefox is a free, open-source web browser from Mozilla
• Google Chrome: Google Chrome is a free, open source web browser developed by Google
• Opera: Opera is a free, fast, small and standard - compliant web browser developed by the Opera Software company
• Netscape: Netscape was the first commercial web browser

A Threat is any circumstance or event with the potential to cause harm to the system or activity in the form of destruction, disclosure, and modification of data, or denial of service. A threat is a potential for harm. 

Some of the common terms associated with threats and their description are as follows:

• Malware: A collective term for malicious software, such as viruses, worms and trojans; designed to infiltrate systems and information for criminal, commercial or destructive purposes.
• Phishing: A form of social engineering, involving the sending of legitimate-looking emails aimed at fraudulently extracting sensitive information from recipients, usually to gain access to systems or for identity theft.
• Spam: Unsolicited email sent in bulk to many individuals, usually for commercial gain, but increasingly for spreading malware.

Spoofing: A spoofing attack is when a malicious party impersonates another device or user on a network in order to launch attacks against network hosts, steal data, spread malware, or bypass access controls. There are several different types of spoofing attacks that malicious parties can use to accomplish this. They are IP Address Spoofing Attacks, ARP (Address Resolution Protocol) Spoofing Attacks, DNS Server Spoofing Attacks, etc.

A software bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.

The function of different materials in an optical fibre are:

• Adhesive aluminium foil:

Protect cable jacket from damage during shrinking of heat shrink sleeves.

• Stainless steel channel under clip:

The stainless-steel channel and under clip is used to close the heat shrink sleeves before shrinking.

• Aluminium canister – Finger coated:

Provide adequate structural strength to avoid collapsing during installation.

• Emery strip

The emery strip is used for surface preparation of cable with PVC/Polyethylene sheath.

• In controlled rectifiers, the nature of load current, i.e. whether load current is continuous or discontinuous depends both on the type of load and firing angle delay
• Highly inductive load makes load current continuous and ripple free
• The average load current supplied by a thyristor depends on firing angle

• The second India-Myanmar bilateral Army exercise named 'IMBEX 2018-19' commenced at Chandimandir military station in Haryana on 14 January 2019.
• The aim of this joint training event is to train the Myanmar delegation for participation in UN peacekeeping operations.
• The exercise includes participation of 15 officers from Myanmar Army and 15 officers from Indian Army

Properties of Diamagnetic, Paramagnetic and ferromagnetic materials placed in the magnetic field is shown in the table

Due to the Class B operation, their collector efficiency is quite high.

• They give more AC output power per device
• Distortion free output is obtained
• Output Transformer used for push-pull amplifier circuit are lighter, smaller and less expensive than the transformers of comparable quality that are used in single-ended circuits
• In the core of the output transformer, the DC components for output currents of the two devices oppose each other magnetically which eliminates the tendency of the core to saturate

In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.

The C Library functions are inbuilt functions in C programming.

The prototype and data definitions of the functions are present in their respective header files and must be included in the program to access them.

Predefined functions:

hello() is a user-defined function.

Power factor: It is the ratio between true power and apparent power
Power factor = kW/kVA

Form factor: It is the ratio of the RMS (root mean square) value to the average value.

Load factor: It is defined as the ratio of the average load over a given period to the maximum demand (peak load) occurring in that period.

Diversity factor: It is the ratio of sum of individual maximum demand to maximum demand on power station