A Carnot engine has an efficiency of 83.0% and performs 4500 J of work every cycle. How much energy is discharged to the lower t
1 answer:
We will start by finding the heat in state one through the thermal efficiency or efficiency of a thermal machine is a coefficient or dimensionless ratio calculated as the ratio of the energy produced (in an operating cycle) and the energy supplied to the machine. Mathematically it is the relationship between the work generated and the heat emanated.
So,
The total change of energy is equivalent to 4500J and this is equal by conservation of energy to the total change in heat. So:
Therefore the energy which is discharged to the lower temperature reservoir every cicle is 921.7J
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17.
There are three different methods for charging objects:
- Friction: in friction, two objects are rubbed against each other. As a result, electrons can be passed from one object to the other, so one object will gain a net negative charge while the other object will gain a net positive charge due to the lack of electrons.
- Conduction: this occurs when two conductive objects are put in contact with each other, and charges (electrons, usually) are transferred from one object to the other one.
- Induction: this occurs when two objects are brought closer to each other, but not in contact. If one of the two objects has a net charge (different from zero) on its surface, then it will induce a movement of charges in the second object: in particular, in the second object, charges of the opposite polarity will be attracted towards the first object, while charges of same polarity will be repelled further away.
18.
Charged objects produce around themselves an electric field. The strenght of the electric field is given by (assuming the charged objects are spherical)
where k is the Coulomb's constant, q is the magnitude of the charge and r the distance from the centre of the charge. As we see, the strength of the field is inversely proportional to the square of the distance.
Also, the direction of the field is determined by the sign of the charge:
- if the charge is positive, the electric field points away from the charge (this means that other positive charges in the field will be repelled away)
- if the charge is negative, the electric field points towards the charge (this means that other positive charges in the field will be attracted towards it)
19.
Electrical force is given by:
where k is the Coulomb's constant, q1 and q2 are the two charges, and r their separation.
Gravitational force is given by:
where G is the gravitational constant, m1 and m2 are the masses of the two objects, and r their separation.
Similarities between the two forces:
- Both are inversely proportional to the square of the distance between the two objects, r
- Both are non-contact forces (the two objects can experience the forces even if they are not in contact)
- Both forces have infinite range
Differencies between the two forces:
- The electric force can be either attractive or repulsive, while the gravitational force is attractive only
- The electric force is much stronger than the gravitational force, due to the much larger value of the Coulomb's constant k compared to the gravitational constant G