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The energy of a body is its capacity of doing work. There are many forms of energy like mechanical, thermal energy, light energy, nuclear energy, electrical energy, etc.
Mechanical energy, E = Kinetic energy (K.E.) + Potential energy (P.E.)
- The energy possesses by a body due to its motion is called kinetic energy. For a body of mass m moving with velocity v, the kinetic energy formula is given by
K.E = 1/2 mv2
- The energy possesses by a body due to its position is called potential energy. For a body of mass m and at height h, the potential energy is given by
P.E. = mgh
According to the law of conservation of energy, “Energy can be created nor be destroyed but it can change from one form to another form”.
This law is applicable to all forms of energy present in the universe. The examples of forms of energy that we use by converting it into another form in our daily life are
- Energy obtained from the sun can be converted into electric energy.
- Also, wind energy can be converted into electrical energy.
- The electric energy of the induction cooker is converted into heat energy for cooking food.
Very Short Answers Questions [1 Mark Questions]
Ques. Define energy and write its SI unit and dimensional formula.
Ans. Energy is defined as the ability of a system to do work. It is a scalar quantity.
The SI unit of energy is Joule (J).
The dimensional formula of energy is [M L2 T-2].
Ques. Which form of energy is associated with the motion of the object?
Ans. The energy associated with the motion of an object is known as kinetic energy.
The kinetic energy of a body of mass m moving with velocity v is given by
K.E. = 1/2 mv2
Ques. Which of the following is a form of energy?
- 100 oC
- Temperature
- Heat
- Mass
Ans. The correct option is c. Heat.
Explanation: Heat is a form of energy that is transferred from one object to another due to its temperature difference.
Ques. Which statement about energy is true?
- Energy can be created
- Energy can be destroyed
- Energy can pass through a vacuum
- None of the above
Ans. The correct option is c. Energy can pass through a vacuum.
Explanation: Energy can pass through a vacuum in the form of electromagnetic waves.
Ques. Which among the following is not a type of primary resource?
- Coal
- Sunlight
- Crude oil
- Hydrogen energy
Ans. The correct option is d. Hydrogen energy
Explanation: Hydrogen energy is not a primary source of energy because it is obtained from primary sources like fossil fuels, therefore hydrogen energy is considered to be a secondary source of energy.
Short Answers Questions [2 Marks Questions]
Ques. Define energy yield ratio.
Ans. The energy yield ratio refers to the measure of the efficiency of the energy conversion process. It is calculated by dividing the energy output of a system by the energy input.
Ques. Which form of energy is associated with the flow of electric charges?
Ans. The energy associated with the flow of electric charges is known as electrical energy. It is produced when electrons, which are negatively charged particles, are set in motion through a conducting medium.
Ques. Which form of energy is associated with the vibrations of particles in a medium?
Ans. The energy associated with the vibrations of particles in a medium is known as Sound energy. It is produced when a source creates mechanical disturbances in the medium, that cause the particles in the medium to vibrate and propagate as sound waves.
Ques. Explain the concept of thermal energy and how it is related to the temperature of a substance.
Ans. The internal energy of a substance that causes by the motion of its particles is known as thermal energy, also called heat energy. As the temperature is a measure of the average kinetic energy of the particles within the substance, therefore it is directly related to the thermal energy of the substance. Higher temperature indicates greater thermal energy and vice-versa.
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Long Answers Questions [3 Marks Questions]
Ques. What are renewable and non-renewable sources of energy?
Ans. Renewable sources of energy are those that can be replenished naturally or cannot be depleted over time. Wind energy, solar energy, and geothermal energy are examples of renewable sources of energy.
Non-renewable sources of energy exist in finite amounts, and once they are depleted, they cannot be replenished. Coal, oil, and natural gases are examples of non-renewable sources of energy.
Ques. What is potential energy and how is it different from kinetic energy?
Ans. Potential energy is defined as the energy possessed by an object due to its change in position or change in shape. It is stored energy and has the potential to be converted into other forms of energy.
Examples of potential energy are gravitational potential energy, elastic potential energy, etc.
While kinetic energy is the energy possessed by an object due to its motion. The kinetic energy of a body depends on its mass and velocity.
Ques. What is nuclear energy and how is it produced?
Ans. The energy obtained from the conversion of nuclear mass is known as nuclear energy. It can be produced from radioactive elements by two process
- Nuclear fission: It is a process of splitting a heavy nucleus into two lighter nuclei releasing a large amount of energy.
- Nuclear fusion: It is a process in which two very light nuclei combine to form a nucleus with a larger mass number along with the simultaneous release of a large amount of energy.
Very Long Answers Questions [5 Marks Questions]
Ques. What are the different forms of energy? Explain with examples. Discuss how energy can be converted from one form to another.
Ans. The different forms of energy are
Mechanical Energy: The energy associated with the motion or position of an object is called mechanical energy. The kinetic energy of a moving car and the potential energy stored in a stretched spring are examples of mechanical energy.
Thermal Energy: The energy associated with the motion of particles within a substance is known as Thermal energy. It is also known as heat energy. Energy obtained from sunlight is an example of heat energy.
Chemical Energy: The energy stored in the bonds between atoms and molecules is called chemical energy. Energy is released or absorbed when these bonds are broken or formed. Energy stored in food and the energy released during a chemical reaction is examples of chemical energy.
Electrical Energy: The energy carried by electric charges is known as electrical energy. This energy is used to power electrical devices. Electricity flowing through a lightbulb and the electrical signals in the human nervous system are examples of electrical energy.
Light Energy: The electromagnetic energy that can be detected by the human eye is known as Light energy. It is also known as radiant energy. It can be emitted, reflected, or transmitted by objects. Sunlight, light bulbs, and lasers are examples of light energy.
Conversion of Energy: There are various processes through which energy is converted from one form to another form. The law of conservation of energy states that energy cannot be created or not destroyed, but it can be converted from one form to another.
Some common energy conversions are:
- Conversion of mechanical energy to electrical energy through a rotating turbine.
- Conversion of chemical energy to thermal energy when fuel is burnt.
- Conversion of electrical energy to light energy when electricity passes through a light bulb.
- Conversion of potential energy to kinetic energy when an object falls from a height.
Ques. Discuss the advantages and disadvantages of renewable sources of energy.
Ans. The advantages of renewable sources of energy are
- They are almost inexhaustible, therefore available for the long term.
- They have minimal impact on the environment and reduce greenhouse gas emissions.
- They promote local economic development.
The disadvantages of renewable sources of energy are
- The cost of renewable energy systems setup can be high.
- The power produced by renewable sources of energy is intermittent because they depend on the weather (e.g., sun, wind).
- Some renewable technologies, such as large-scale hydropower dams have adverse effects on ecological systems.
Ques. Discuss the advantages and disadvantages of non-renewable sources of energy.
Ans. The advantages of non-renewable sources of energy are
- Non-renewable sources of energy such as coal, petroleum, and natural gas, are widely available in many parts of the world.
- Non-renewable sources of energy are cost-effective in terms of extraction, production, and distribution.
- They can provide a continuous and reliable supply of power.
The disadvantages of non-renewable sources of energy are
- Non-renewable sources of energy are finite and will eventually run out.
- The extraction and combustion of coal, petroleum, and natural gas release greenhouse gases that contribute to global warming and climate change.
- They release pollutants that contribute to air pollution and have adverse effects on human health and ecosystems.
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