Q16 of 19 Page 374

A battery lights a bulb. Describe the energy change involved in the process.

When the bulb is connected to the battery the chemical energy of the battery is converted into the electrical energy. When bulb receives this electrical energy it converts it into light and heat energy. The figure below shows the energy transformation in more descriptive way.

Chemical Energy → Electrical Energy → Light Energy + Heat Energy


More from this chapter

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14

Two bulbs of 40W each are lighted for eight hours daily. Find the cost of electrical energy consumed by them in one week at Rs. 3 per unit.

 15

A man whose mass is 50 kg moves up 15 steps each of height 15 cm in 45 seconds of time. Calculate the power used in climbing those stairs. (g = 10 m/s2)

 16

Calculate the amount of work needed to stop a car of 500 kg, moving at a speed of 36 km/h.

 17

Rashmi was playing on a swing in a park. To increase her speed when her swing was at its lowest position during its oscillations she pushed the ground hard with her feet. She enjoyed it but could not understand the mechanism. Her elder brother Pankaj explained her the reason, when she asked him.

(i) What type of energy was possessed by Rashmi while swinging? On what factors does it depend?


(ii) Why did the swing’s speed increase on pushing the ground harder with feet?


(iii) Why and what did Rashmi ask Pankaj?