Question Discussion & Solution

The correct answer is Authentication.

Key Points

• MAC stands for message authentication code.
• A message authentication code is an authentication tag (also called a checksum) derived by application of an authentication scheme, together with a secret key, to a message.
• MACs can be categorized as - 
  • Unconditionally secure
  • Hash function-based
  • Stream cipher based
  • Block cipher based

CONCEPT:

Electric Charge: It is a physical property of a matter that experiences a force when placed in an electromagnetic field.

• Electric charges create electric fields.

• Two types of charges are found – 1.) Positive charge. 2.) Negative charge
• Force experienced when charge placed in the electromagnetic field is \({{F}^{\to }}=q\times {{E}^{\to }}\) where q = charge of the body (in coulomb). \({{E}^{\to }}\) = intensity of the electric field.
• SI unit of charge is Coulomb and the symbol is C. One coulomb is equal to the charge on 6.241 x 10¹⁸ protons.

Inductor: It is a passive electric component that stores energy in the form of magnetic field lines. It is a simple loop of wire.

• The inductance of the inductor could be measured by equation L = Φ / I where ϕ is magnetic flux and I is a current flowing through it.
• SI unit of inductance is Henry.
• Energy stored in Inductor U = ½ (LI²).

Capacitor: It is a device consisting of two conducting "plates" separated by an insulating material (dielectric). It stores energy in the form of an electric field with the help of an electric charge.

• The capacitance of a capacitor is measured by equation C = q /Δ v where q is charge and ∆ V is a potential difference.
• SI Unit of capacitance is Farad.
• Energy stored in Capacitor U = ½ (CV²)

Resistance: It is a measure of how the device reduces the flow of electric current, basically it opposes the flow of charges.

• Further, it states the ratio of the applied voltage to electric current flows through it.
• R = V/I [R is resistance, V is the potential difference and I is electric current].
• Also, R = ρ × (L/A) [where ρ is specific resistance of the material, l is the length of conductor and A is the cross-sectional area of the conductor].
• The unit of resistance is volt/ampere or ohm (Ω).
• It does not store energy.

Transformer: It is an electrical device that converts A/C current from one voltage to another.

EXPLANATION:

• A capacitor stores energy in the form of electrical charges and fields.
• Here, C_o = Capacitance, V = voltage, A = area of the plates, d = distance between them.

\(\Rightarrow {{C}_{o}}=\frac{{{Q}_{o}}}{V}=\frac{{{\epsilon }_{o}}A}{d}\)

Important Points

• Remember Electric field lines are stored in capacitor & magnetic field lines are stored in Inductor.

Four members: A, B, C, D

Using the symbols in the table given below, we can draw the following family tree:

1) B is the husband of A

2) C is the sister of B

3) D is the brother of A

Hence, C is D’s brother-in-law's sister.

The correct answer is Hydrocarbons.

Key Points

• The compounds which are formed by the covalent bond between carbon & hydrogen, are known as hydrocarbons.
• These are also known as 'parent compound'.
• Carbon is placed in the Second period.
• The atomic number of carbon is 6 while the weight is 12.
• Carbon needs 4 electrons to complete the octet state and it is full filled by covalent bonds.

Additional Information

•  Examples of Hydrocarbon.
• Natural Gas:
  • Natural gas contains 97% of Methane.
  • It is a colourless highly flammable gaseous hydrocarbon.
  • It is used as fuel for generating electricity and heat.
  • Natural gas is a compressed form that is used as fuel for vehicles which is known as CNG.
  • This is used for making fertilizers also, mainly ammonia.
• Methane:
  • Methane was discovered by the Italian scientist Alessandro Volta between 1776-1778 while he was studying the gases found in marshy land.
  • Melting Point- -182.5 degree
  • Boiling point- -161.5 degree
  • Methane gas is colourless and is less dense than water.
  • This gas is highly inflammable. While burning with oxygen it has a bluish flame.

Total = Top + Bottom – 1

25 = 12 + Bottom – 1

25 – 11 = Bottom

Bottom = 14^th