Given:
Energy consumed when heating is maximum at the given rate \((P_{1})=420 \mathrm{~W}\)
Energy consumed when heating is minimum at a given rate \(P_{2}=180 \mathrm{~W}\) 
Applied voltage = 220 V
Current in each case = ?
\(\mathbf{P}=\mathbf{V} \times \mathbf{I}\)
case (i) : \(\mathrm{I}_{1}=\frac{\mathrm{P}_{1}}{\mathrm{~V}}=\frac{420}{220}=1.9 \mathrm{~A}\)
case (ii) : \(\mathrm{I}_{2}=\frac{\mathrm{P}_{2}}{\mathrm{~V}}=\frac{180}{220}=\mathbf{0 . 8 1} \mathbf{A}\)

R₁ = 1 Ω, R₂ = 2 Ω, R₃ = 4 Ω Current I₁ = 1 A
The potential difference across the 1 Ω resistor = I₁ R₁ = 1 × 1 = 1 V
Since, the resistors are connected in parallel in the circuit, the same potential difference will exist across the other resistors also.
So, the current in the 2 Ω resistor, \(\frac { V }{ { R }_{ 2 } } =\frac { 1 }{ 2 } =0.5A\)
Similarly, the current in the 4 Ω resistor,
\(\frac { V }{ { R }_{ 3 } } =\frac { 1 }{ 4 } =0.25A\)

(i) Electric heater.
(ii) Electric iron work on the heating effect of current.

(i) The SI unit of current is ampere (A).
(ii) The current flowing through a conductor is said to be one ampere, when a charge of one coulomb flows across any cross-section of a conductor  in one second. 
\(1\ ampere=\cfrac { 1\ coulomb }{ 1\ second } \)

(a) Advantages of LED television:
(i) LED television has brighter picture quality
(ii) It is thinner in size
(iii) It uses less power and consumes very less energy.
(iv) Its life span is more.
(v) It is more reliable
(b) Merits of LED bulb:
(i) As there is no filament, there is no loss of energy in the form of heat. It is cooler than the incandescent bulbs
(ii) In comparison with the fluorescent light, the LED bulbs have significantly low power requirement.
(iii) It is not harmful to the environment
(iv) A wide range of colours is possible here.
(v) It is cost-efficient and energy efficient.
(vi) Mercury and other toxic materials are not required.
(vii) One way of overcoming the energy crisis is to use more LED bulbs.