1. In a hydroelectric power plant, the energy of stored water is first converted mainly into:
(A) Nuclear energy
(B) Kinetic energy
(C) Chemical energy
(D) Sound energy
Answer: (B) Kinetic energy
Explanation: Water stored at a height has gravitational potential energy. As it falls, this is converted into kinetic energy, which ultimately helps generate electrical energy.
2. The ultimate source of energy in a hydroelectric power plant is:
(A) Chemical energy of water
(B) Gravitational potential energy of water
(C) Nuclear energy of water
(D) Solar energy stored in water
Answer: (B) Gravitational potential energy of water
Explanation: Water stored at a height possesses gravitational potential energy, which is converted into kinetic and then electrical energy.
3. A dam is constructed at a considerable height mainly to:
(A) Increase the temperature of water
(B) Increase the gravitational potential energy of water
(C) Decrease the mass of water
(D) Increase the chemical energy of water
Answer: (B) Increase the gravitational potential energy of water
Explanation: Greater height gives stored water greater gravitational potential energy.
4. As water flows downward from a dam, its:
(A) Potential energy increases
(B) Kinetic energy decreases
(C) Potential energy is converted into kinetic energy
(D) Chemical energy is converted into nuclear energy
Answer: (C) Potential energy is converted into kinetic energy
Explanation: The loss of height causes gravitational potential energy to be converted into kinetic energy.
5. In a hydroelectric power station, the turbine primarily converts:
(A) Electrical energy into mechanical energy
(B) Kinetic energy of water into mechanical energy
(C) Chemical energy into electrical energy
(D) Solar energy into mechanical energy
Answer: (B) Kinetic energy of water into mechanical energy
Explanation: Moving water rotates the turbine. The generator then converts the turbine’s mechanical energy into electrical energy.
6. The energy transformation in a hydroelectric power plant is best represented as:
(A) Electrical → mechanical → potential
(B) Potential → kinetic → mechanical → electrical
(C) Chemical → kinetic → electrical
(D) Nuclear → mechanical → electrical
Answer: (B) Potential → kinetic → mechanical → electrical
7. A swinging pendulum continuously undergoes conversion between:
(A) Heat and sound energy
(B) Chemical and electrical energy
(C) Potential and kinetic energy
(D) Nuclear and chemical energy
Answer: (C) Potential and kinetic energy
Explanation: At the highest point, potential energy is maximum; as the pendulum falls, it changes into kinetic energy.
8. At the extreme position of a swinging pendulum, its:
(A) Kinetic energy is maximum
(B) Potential energy is maximum
(C) Both kinetic and potential energies are zero
(D) Speed is maximum
Answer: (B) Potential energy is maximum
9. At the lowest position of an ideal swinging pendulum, its:
(A) Kinetic energy is maximum
(B) Potential energy is maximum
(C) Speed is zero
(D) Total mechanical energy is zero
Answer: (A) Kinetic energy is maximum
10. When a bow is stretched before releasing an arrow, the energy stored in the bow is:
(A) Chemical energy
(B) Elastic potential energy
(C) Kinetic energy
(D) Electrical energy
Answer: (B) Elastic potential energy
11. The energy stored in a stretched rubber band is mainly:
(A) Gravitational potential energy
(B) Elastic potential energy
(C) Nuclear energy
(D) Thermal energy
Answer: (B) Elastic potential energy
12. When a stretched bow is released, the stored elastic potential energy is mainly converted into:
(A) Kinetic energy of the arrow
(B) Nuclear energy
(C) Chemical energy
(D) Electrical energy
Answer: (A) Kinetic energy of the arrow
13. A spring toy that has been compressed stores:
(A) Elastic potential energy
(B) Chemical energy
(C) Nuclear energy
(D) Sound energy
Answer: (A) Elastic potential energy
14. When a compressed spring is released, its stored energy is mainly converted into:
(A) Kinetic energy
(B) Nuclear energy
(C) Chemical energy
(D) Gravitational energy only
Answer: (A) Kinetic energy
15. When a hammer drives a nail into a piece of wood, the hammer does:
(A) No work
(B) Mechanical work
(C) Electrical work
(D) Nuclear work
Answer: (B) Mechanical work
Explanation: A force is applied to the nail and the nail undergoes displacement in the direction of the applied force.
16. Which condition is necessary for mechanical work to be done on an object?
(A) Force must act, but displacement is unnecessary
(B) Displacement must occur due to a force
(C) The object must be at rest
(D) The object must have zero mass
Answer: (B) Displacement must occur due to a force
17. A person pushes a heavy wall with great force, but the wall does not move. The mechanical work done on the wall is:
(A) Maximum
(B) Zero
(C) Negative
(D) Infinite
Answer: (B) Zero
Explanation: Mechanical work requires displacement. Since the wall does not move, work done on the wall is zero.
18. When a cyclist pedals a bicycle, the primary energy transformation in the cyclist’s body is:
(A) Chemical energy → mechanical energy
(B) Electrical energy → chemical energy
(C) Nuclear energy → mechanical energy
(D) Mechanical energy → chemical energy
Answer: (A) Chemical energy → mechanical energy
Explanation: Chemical energy stored in food is converted into muscular energy and then mechanical energy used to move the bicycle.
19. The energy used by a cyclist to move a bicycle forward ultimately comes mainly from:
(A) Sound energy
(B) Chemical energy from food
(C) Nuclear energy
(D) Magnetic energy
Answer: (B) Chemical energy from food
20. An electric motor converts:
(A) Mechanical energy into electrical energy
(B) Electrical energy into mechanical energy
(C) Chemical energy into electrical energy
(D) Heat energy into nuclear energy
Answer: (B) Electrical energy into mechanical energy
21. Which device is commonly used to convert electrical energy into mechanical energy?
(A) Generator
(B) Electric motor
(C) Solar cell
(D) Transformer
Answer: (B) Electric motor
22. The rotating blades of an electric fan demonstrate the conversion of:
(A) Mechanical energy into electrical energy
(B) Electrical energy into mechanical energy
(C) Chemical energy into electrical energy
(D) Solar energy into chemical energy
Answer: (B) Electrical energy into mechanical energy
23. An electric motor is commonly found in:
(A) Electric fans
(B) Water pumps
(C) Washing machines
(D) All of the above
Answer: (D) All of the above
24. An electric generator converts:
(A) Electrical energy into mechanical energy
(B) Mechanical energy into electrical energy
(C) Chemical energy into heat energy
(D) Solar energy into mechanical energy
Answer: (B) Mechanical energy into electrical energy
25. Which device works on the principle of electromagnetic induction and converts mechanical energy into electrical energy?
(A) Electric motor
(B) Generator
(C) Electric heater
(D) Battery
Answer: (B) Generator
26. In a bicycle dynamo, the mechanical energy of the rotating wheel is converted into:
(A) Chemical energy
(B) Electrical energy
(C) Nuclear energy
(D) Sound energy
Answer: (B) Electrical energy
27. A solar cell converts:
(A) Electrical energy into solar energy
(B) Solar energy into electrical energy
(C) Mechanical energy into solar energy
(D) Chemical energy into electrical energy
Answer: (B) Solar energy into electrical energy
28. The conversion of sunlight directly into electricity in a solar cell is known as:
(A) Photoelectric effect
(B) Photovoltaic effect
(C) Electromagnetic induction
(D) Heating effect
Answer: (B) Photovoltaic effect
29. Which of the following represents the correct energy transformation in a solar cell?
(A) Electrical → solar
(B) Solar → electrical
(C) Mechanical → electrical
(D) Chemical → mechanical
Answer: (B) Solar → electrical
30. Which pair is correctly matched?
(A) Electric motor — Mechanical to electrical
(B) Generator — Electrical to mechanical
(C) Solar cell — Solar to electrical
(D) Bow and arrow — Chemical to electrical
Answer: (C) Solar cell — Solar to electrical
31. Which of the following is an example of conversion of potential energy into kinetic energy?
(A) Water falling from a dam
(B) Electric motor running
(C) Solar cell producing electricity
(D) Generator producing electricity
Answer: (A) Water falling from a dam
32. Which of the following stores elastic potential energy?
(A) Stretched bow
(B) Moving car
(C) Flowing river
(D) Rotating fan
Answer: (A) Stretched bow
33. A moving object possesses:
(A) Kinetic energy
(B) Only potential energy
(C) Only chemical energy
(D) No energy
Answer: (A) Kinetic energy
34. The energy possessed by an object because of its position or height is called:
(A) Kinetic energy
(B) Potential energy
(C) Thermal energy
(D) Sound energy
Answer: (B) Potential energy
35. Which of the following is an example of mechanical energy being converted into electrical energy?
(A) Electric fan
(B) Generator
(C) Solar cell
(D) Electric heater
Answer: (B) Generator
36. Which of the following is an example of electrical energy being converted into mechanical energy?
(A) Generator
(B) Solar cell
(C) Electric motor
(D) Battery
Answer: (C) Electric motor
37. A falling stone converts:
(A) Kinetic energy into potential energy
(B) Potential energy into kinetic energy
(C) Chemical energy into electrical energy
(D) Electrical energy into mechanical energy
Answer: (B) Potential energy into kinetic energy
38. Which of the following correctly represents the energy conversion in a bow and arrow?
(A) Chemical → electrical
(B) Elastic potential → kinetic
(C) Electrical → potential
(D) Nuclear → kinetic
Answer: (B) Elastic potential → kinetic
39. Which device primarily demonstrates the conversion of mechanical energy into electrical energy?
(A) Motor
(B) Generator
(C) Heater
(D) Refrigerator
Answer: (B) Generator
40. Which one of the following is incorrectly matched?
(A) Hydroelectric plant — Potential energy of water
(B) Electric motor — Electrical to mechanical
(C) Generator — Mechanical to electrical
(D) Solar cell — Electrical to solar
Answer: (D) Solar cell — Electrical to solar
Explanation: A solar cell converts solar energy into electrical energy, not the reverse.