Electrical Power, Energy Consumption, and Cost

Attempt either (a) or (b):

(a) A smart home uses an energy monitoring system to track electricity usage of appliances. In a month of 30 days, the following devices are used:

1. An electric heater of $1500\text{ W}$ used for $4\text{ hours}$ daily.
2. A microwave oven rated at $1.5\text{ kW}$ used for $3\text{ hours}$ daily.

(i) Define electric power and write its SI unit. (ii) Calculate the total energy consumed in joules and $kWh$ in a whole month. (iii) Find out the total cost of electricity for running both appliances for a month of 30 days if the cost of 1 unit is ₹7.

OR

(b) (i) What is meant by electrical resistivity of a material? (ii) A series electric circuit comprising a resistor made of a metallic wire has an ammeter which reads $300\text{ mA}$. If the length of the wire is made three times, what will be the new reading in the ammeter? (iii) Calculate the resistance of a $500\text{ m}$ long aluminium wire of cross-sectional area $1 \times 10^{-3}\text{ m}^2$ and resistivity $2.65 \times 10^{-8}\,\Omega\cdot\text{m}$.