Question Discussion & Solution

For alphabet: Increase by + 4

 D + 4 → H + 4 → L + 4 → P + 4 → T + 4 → X

For Number: Decrease number by - 4

23 – 4 → 19 – 4 → 15 – 4 → 11 – 4 → 7 – 4 → 3

The correct answer is Electric Heater.

Key Points

• Electric Heater is a device that can convert Electric energy into heat energy.
• In an electron tube, an electric heating element shaped in the form of a wire or ribbon is used to supply heat to a cathode; the element provides heat when a current is passed through it.
• Electric heaters also are used for domestic central heating and for materials processing in the industry for example heat pumps; electric furnace.

Additional Information

• Energy is the ability to do work.
• The  Law of conservation of energy:
  • Energy can neither be created nor be destroyed, only Energy can be converted from one form to another.
• These are some parts of the energy that convert one form to another:
  • Heat
  • Light
  • Motion
  • Electrical
  • Chemical
  • Gravitational

Important Points

Concept:

• Atoms are made up of subatomic particles - electrons protons and neutrons.
• In the center of an atom, a nucleus is present which contains protons and neutrons together known as nucleons.
• The mass of an atom is most concentrated at the center of the atom, i.e. the nucleus.

​Electrons:

• Discovered by Sir J.J Thomson in the year 1897.
• Previously named as cathode rays as they were supposed to be emitted from the cathode.
• They are deflected towards the positive side.
• They have high kinetic energy.
• They are deflected by an electric and magnetic field.
• It has a negative charge of

  \(charge=1.602\times10^{-19} coulombs \)
\(mass={1\over 1837}\times 9.107\times 10^{-28}g\)

Protons:

• Discovered by Goldstein.
• Depicted first as positive rays because it seemed to emerge from the anode.
• Mass of a proton is

 \(1.670 \times 10^{- 24}g\)

\(Charge=1.602\times 10^{-19} coulombs\)​

Explanation:

• Rutherford's discovery led to the discovery of nucleus.
• He found out that most of the mass of the nucleus is situated in its centre and contains the positively charged particles protons.
• The atom is otherwise empty and as electrons have negligible mass, the mass of an atom should be equal to the sum of mass of protons present in it.
• However, it was seen that in Helium, there are only two protons, so its mass should be twice the mass of each proton = \(2\times 1.008 a.m.u\).
• Experimental results revealed that it has a mass of 4.003a.m.u.
• Hence, it was concluded that the nucleus has particles containing no charge but mass almost equal to that of a proton.
• This was established by scientist James chadwick in 1932.

Additional Information

Rutherford's gold foil experiment: 

• He discovered the atomic nucleus and gave us an atomic model.
• He directed alpha particles towards a metal sheet.
• He saw that most of the alpha particles, which are positively charged particles, are not getting deflected.
• Most of the alpha particles emerged undeflected.

• Therefore, he concluded that most of the mass of the nucleus is situated in its centre and contains the positively charged particles protons.
• Electrons revolve around the nucleus in certain orbits.

Thus, ‘SEDATE’ can be coded as:

Concept:

Resistance: The property of electrical materials and electrical instruments that opposes the flow of current through them is called resistance.

It is denoted by R. The SI unit of resistance is the ohm (Ω).

Power: The rate of work done by an electric current is called power. It is denoted by P. The SI unit of power is the watt (W).

Power dissipation (P) is given by:

\(P=VI=\frac{V^2}{R}=I^2R\)

Where V is the potential difference across resistance, I is current flowing and R is resistance.

Calculation:

With R = 50 Ω, and V = 220 V, the power required by the bulb will be:

\(P=\frac{V^2}{R}=\frac{220\times 220}{50}\)

P = 968 W