Question

14 Electrical energy is sold by PHCN in units of kilowatt-hour (kWh). The lighting of a house is done with five 60W bulbs which are swithed on for approximately three hours per day. What is the lighting bill for the household over a period of 30days at the rate of N1.20 per kilowatt-hour?
N1.50
N25.30
N32.40
N52.20

15 A battery has emf 13.2V and internal resistance
24mΩ
. If the load current is 20.0A, find the terminal voltage o f the battery
12.7V
14.5V
16.8V
17.7V

Answer 1

Answer on Question#55903 - Physics - Electromagnetism

14. Electrical energy is sold by PHCN in units of kilowatt-hour (kWh). The lighting of a house is done with five $W_{0} = 60\mathrm{W}$ bulbs which are switched on for approximately three hours per day. What is the lighting bill for the household over a period of 30 days at the rate of N1.20 per kilowatt-hour?

N1.50

N25.30

N32.40

N52.20

15. A battery has emf $\varepsilon = 13.2\mathrm{V}$ and internal resistance $r = 24\mathrm{m}\Omega$. If the load current is $I = 20.0\mathrm{A}$, find the terminal voltage of the battery

12.7V

14.5V

16.8V

17.7V

Solution:

14. The total power of 5 bulbs is

$$W = 5 W _ {0} = 5 \cdot 6 0 W = 3 0 0 W$$

They are switched on for $t = 30 \cdot 3\mathrm{h} = 90$ hours over the period of 30 days. Therefore the total waste of energy over this period is given by

$$E = W \cdot t = 2 7 \mathrm {k W h}$$

This will cost the following sum for the household

$$S = 2 7 \cdot N 1. 2 0 = N 3 2. 4 0$$

15. The terminal voltage of the battery is given by the difference between its emf and the voltage drop in the internal resistance:

$$V = \varepsilon - I \cdot r = 1 3. 2 V - 2 0 A \cdot 2 4 m \Omega = 1 2. 7 V$$

Answer:

14. N32.40

15. 12.7V

https://www.AssignmentExpert.com