Different forms of energy - class-XI

First the fuel in the engine gives chemical energy during burning. That chemical energy then converts to kinetic energy if the rotor of blades of the helicopter. Then kinetic energy converts in gravitational potential energy as it gains height.

When sunlight falls on plant, some of the energy is trapped through
photosynthesis and is stored in the form of chemical energy which helps the plants to prepare their own food.

$A$: A car moving up a hill.
Moving car has kinetic energy, kinetic energy gets converted to potential energy as it gains height $(h)$.
And potential energy $=mgh$
$B$: Photographic film is exposed to sun -light.
When photographic film is exposed to Sun the silver bromide present in it decomposes, such that the film cannot be developed, here the light energy changes to chemical energy.

While riding a bicycle,the muscular energy of the rider gets transferred to heat energy and kinetic energy of the bicycle.Heat energy heats the rider's body.Kinetic energy provides a velocity to the bicycle to move in rotation.The transformation can be shown as:
Muscular energy$=$kinetic energy+heat energy
During transformation,the total energy remains conserved.

After reaching the ground it will not have any height from the ground hence no potential energy as it is defined as virtue of state of its position where as it has velocity by which it can be said that kinetic energy exists as it is defined by virtue of state of its motion.While falling potential energy keeps on changing in kinetic energy and on reaching the ground all potential energy changes to kinetic energy.Hence there exists only kinetic energy.

The potential energy stored in a reservoir at a given height is converted to kinetic energy (movement energy) which is used to turn a turbine and produce electricity.
Hence, as the water stored in the dam flows out, its potential energy changes to kinetic energy.

Within the electric cell or battery, the chemical energy changes into electrical energy. The electric energy on flowing through the filament of the bulb, first changes into heat energy and then into the light energy.

When ball is at rest it will have only P.E that is
$P.E = mgh$

The kinetic energy on reaching the ground changes into heat energy, sound energy, etc. and therefore gets dissipated to the ground and air.

Iron glows in red colour when it is heated to very high temperature because heat being a form of energy can be transformed into other forms of energy.

The moving coin has kinetic energy initially, after hitting the other coin it transfers its kinetic energy to the other coin and sets it in motion.(In reality some part of energy is also lost as heat energy)

When a stone is thrown upwards, its velocity decreases and height increases. 

The chemical present in the candle burns with oxygen to give out heat.

Option C is not correct because river flows down due to its gravitational potential energy.

Heat is used to generate steam which moves the pistons and thereby converting heat energy to mechanical energy.

A tube light converts $Electrical  \ energy$ to $Light  \ Energy$.

Option A: Electrical bulb converts electrical energy into heat.

Answer is A

Solar heater absorbs light, and thus photons of light are absorbed and the energy contained in them is converted to heat energy, which raises the temperature of water flowing slowly in contact with the plate and thus heat energy is transfered from plate to water.

When water is flowing it posses some kinetic energy and also posses some potential energy wrt to the lower level of the waterfall.

A meteorite has both potential and kinetic energy before entering earth's atmosphere. As it enters and fall towards the surface of earth, frictional heating occurs which is caused by collision with the molecules in the atmosphere which reduces its velocity. Hence the kinetic energy decreases, which is converted into heat energy. Potential energy is continuously decreasing being converted to kinetic energy.

Fuels contain chemical energy stored in them. When fuels are burnt, the chemical energy changes into heat and light energy.

Work is done on the spring to compress it. This work is stored in the spring in the form of its elastic potential energy. When the spring is released, its elastic potential energy gets transformed into the kinetic energy of the ball and the ball flies away.

An electric iron converts electrical energy into heat energy.

when meteorite falls its potential energy is converting into kinetic energy and when it enters earth atmosphere due to air friction its kinetic energy is reduced but potential energy is also decreasing as its height is decreasing , so we can conclude that its first potential energy converts to kinetic energy and then kinetic energy converts to heat energy.

 A generator converts mechanical energy into electrical energy.  Generator works due to this because of electromagnetic induction generated due to this conversion of energy. Also magnetic field is produced which results in generation of voltage that helps the generator to function.

A motor converts electrical energy into mechanical energy.

A candle burns wax (a chemical substance) through combustion, converting the stored chemical energy into heat and light energy.

During photosynthesis, green plants convert light energy into chemical energy stored in the form of food.

A photocell gives out electric current when light is incident on it. So, it converts light energy into electrical energy.

A microphone converts sound energy into electrical energy. All other devices mentioned convert electrical energy into sound energy.

When a battery is not in use, it does not give out electric current. So, the chemical energy stored in it does not get converted.

A running car burns fuel and thus moves. So, it converts chemical energy into mechanical energy.

By charging a battery, we convert electrical energy into chemical energy. A battery, on the contrary, in use, converts chemical energy into electrical energy.

A loud speaker converts electrical energy into sound energy.

The moving parts of a machine get heated due to friction, thus changing a part of mechanical energy into heat energy.

A thermocouple converts heat energy into electrical energy.

While paddling a bicycle muscular energy converted to kinetic energy as the bicycle moves.Rotation of wheel create friction causing loss of kinetic energy in the form of heat.

Using Einstein's mass-energy equivalence formula E = mc^2, where m = 1kg and c = 3 * 10^8 m/s, E = 1 * (3 * 10^8)^2 = 9 * 10^16 Joules.

During explosion, the chemical energy gets converted into kinetic energy. So, after explosion sum of kinetic energies of all the particles is greater than the initial kinetic energy.

Hydroelectric power plant uses the potential energy stored in water to generate electricity.
Therefore, if we increase the height of it's fall, energy stored will also increase and large amount of potential energy will be converted into kinetic energy, which means more electric energy will be generated.

The energy that we harness from a windmill is the wind energy due to moving air.
Here, option B is wrong as the wind energy does not depend on the altitude when we harness energy from the windmill.

Rubbing hands involves the movement of muscles (mechanical energy), and the friction generated converts that motion into heat energy.

Potential energy = mgh = 5 * 9.8 * 30 = 1470 Joules. Since 1 calorie is approximately 4.2 Joules, 1470 / 4.2 = 350 calories.

The potential energy lost by the falling lead piece is converted entirely into heat energy in the slab and lead, assuming no heat loss. Using mgh = m * s * Delta T, where m cancels out, we find Delta T = (g * h) / s. Substituting g = 9.8 or 9.81, h = 100m, and specific heat s = 30.6 cal/kg C (converted to joules if needed, or using direct units where 1 cal = 4.184 J), the temperature increase calculates to approximately 7.62 degrees Celsius.

For a reversible refrigerator, the coefficient of performance is COP = T_L / (T_H - T_L) = 273 / (300 - 273) = 273 / 27. The heat delivered to the surroundings is Q_H = W + Q_L. Since COP = Q_L / W, Q_L = COP * W = (273 / 27) * 1 = 273 / 27 J. Then Q_H = W + Q_L = 1 + 273 / 27 = 300 / 27 = 11.11 J, which is nearly 11 J.

Energy has dimensions [M L^2 T^-2]. If force [M L T^-2] and length [L] are tripled, then [M L T^-2] -> 3 and [L] -> 3. This implies [M] -> 3 / 3 = 1 and [T^-2] -> 3 / 3 = 1 (no change). Thus, energy scales by [M] * [L]^2 * [T^-2] = 1 * 3^2 * 1 = 9. New energy = 81 * 9 = 729 J.

The work done in a phase change where volume increases is given by W = P * Delta V. Assuming atmospheric pressure P = 1.013 * 10^5 N/m^2 and the change in volume Delta V = 1671 c.c. = 1671 * 10^-6 m^3, multiplying these gives W = (1.013 * 10^5) * (1671 * 10^-6) = 169 J, which is approximately 167 J considering standard approximations for atmospheric pressure and conversion.

By international convention, one calorie is defined precisely as the amount of heat required to raise the temperature of 1 gram of pure water from 14.5 degrees Celsius to 15.5 degrees Celsius at a standard pressure of 760 mm of Hg.

Given,

Heat required = mass * specific heat * delta T = 3000 g * 1 cal/g C * 50 C = 150,000 cal = 630,000 J. Fuel consumption rate = Total heat / Heat of combustion = 630,000 J / 40,000 J/g = 15.75 g.

Supplied heat at constant pressure, 

Initial kinetic energy = 0.5 * m * v^2 = 0.5 * 1 * 50^2 = 1250 J. Half of this is 625 J. Convert to calories: 625 / 4.2 = 148.8 cal. Heat = ms(delta T) -> 148.8 = 200 g * 0.105 cal/g C * delta T. delta T = 148.8 / 21 = 7.08 C.

The chemical energy possessed by the bomb after explosion converts into heat energy, sound energy, light energy i.e. into different forms of energy but remains conserved. Hence, total energy of bomb does not change, but kinetic and mechanical energy changes.

Efficiency of Carnot engine = 1 - (T_low / T_high) = 1 - (400 / 500) = 0.2. Work done = Efficiency * Heat absorbed = 0.2 * 6 * 10^4 = 1.2 * 10^4 J.

$\begin{array}{l} The, , change, , in, , mechanic, , energy, , \Delta U=mg\left( { h+x } \right) +\frac { 1 }{ 2 } m{ v^{ 2 } } \ here, , m=5g=0.00, 5kg\cdot h=19.5, mx=50cm=0.5m,v=10, m/s \ So,, \Delta U=0.005\times 10919.5+0.5+\frac { 1 }{ 2 } \times 0.005\times { \left( { 10 } \right) ^{ 2 } }=0.005\times 10\times 20+\frac { 1 }{ 2 } \times 0.005\times 100=1.25J \end{array}$

Initial KE = 0.5 * 50 * 5.38^2 = 723.6 J. Heat = 723.6 J. Mass melted = Heat / Latent heat = 723.6 / 334,000 J/kg = 0.00216 kg = 2.16 g.

When an ice block falls and 75 percent of it melts due to friction and thermal conversion, the heat required for melting (Q = m_melt * L_f) comes from the loss of potential energy (m * g * h). Since 75 percent melts, 0.75 * m * L_f = m * g * h. Using the latent heat of fusion of ice (approx 3.34 * 10^5 J/kg) and g = 10, solving for height h yields approximately 25.2 Km.

0.5 * (0.5 * m * v^2) = m * s * delta T * J. 0.25 * m * v^2 = m * s * delta T * J. delta T = v^2 / (4 * J * s).

Heat released by steam condensing: x * L_v = x * 540 cal. Heat absorbed by ice melting and warming: Y * L_f + Y * 1 * 100 = Y * 80 + Y * 100 = 180Y. Equating: 540x = 180Y. x/Y = 180/540 = 1/3.

Heat Q = ms(delta T). 4180 J = 1 kg * 4180 J/kg C * delta T. delta T = 1 C.

The maximum work obtainable from a heat engine operating between two temperatures is given by Carnot efficiency: eta = 1 - (T_L / T_H). Here T_H = 127 + 273 = 400 K and T_L = 27 + 273 = 300 K. Thus eta = 1 - (300 / 400) = 1/4 = 0.25. For 1 J of energy extracted from the hot body, the maximum work done is W = eta * Q_H = (1/4) * 1 = 1/4 J.

The chemicalenergy stored in batteries gets transformed into electrical energy through the wires. This then gets transformed into light energy that you see.

Some organisms like the glow worm have chemicals in them, which produce light.

The chemical energy of the fuel is converted to kinetic energy using the engine of the bike.

A tubelight converts electrical energy into light energy.

An electric heater is used to obtain heat energy. For light energy a bulb or other light sources are used.
An electric heater is used to convert electrical energy to heat energy.

Plant takes heat from the sun in form of solar energy and using photosynthesis process, this energy is converted to carbohydrates.

Wind power is generated by the force wind exerts on the blades of a turbine, causing the turbine's shaft to rotate at a speed of 10 to 20 revolutions per minute (rpm). The rotor shaft is connected to a generator that converts mechanical energy into electrical energy.

Considering ground as zero potential
Initially $E = U + K = U + 0 = U$
Finally $E = U + K = 0 + 0 = 0$
So, initially it had some potential energy, it was converted to kinetic energy by gaining speed, it finally became zero so energy must have been lost as heat while applying brakes.

Water is slightly warmer at the bottom of a waterfall than at the top because the gravitational potential energy is converted first to kinetic energy of the falling water, and finally to heat energy as it comes to rest at the bottom.

When water falls from top of a waterfall, it has a force of friction being exerted on it due to which some of its kinetic energy gets converted into heat energy.

The vibrations of the pendulum die after some time , it is because of the frictional force of air which opposes the motion of bob .So air resistance is responsible for the loss in mechanical energy .

First of all moving water is stored against a dam and then it is allowed to fall on turbine and then as turbine rotates it will produce electricity.

An electric heater is an electrical device that converts electric current to heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating: an electric current passing through a resistor will convert that electrical energy into heat energy.

The potential energy of the stored water is converted into kinetic energy which is then converted into electrical energy.
The potential energy of water $= mgh$        ...... (1)
The volume of water $= 10000  {m}^{3}$.
The mass of water $=$ volume $\times$ density $= 10000 \times 1000 = {10}^{7}  kg$.
Also, the depth of water $= 20  m$.
$\therefore$ The height of CG of stored water $= 10  m$.
The total height through which water falls $= 20  m$.
Substituting it in (1), we get potential energy of water $= {10}^{7} \times 20 \times 10 = 2000  MJ$.