Energy in systems (thermal, chemical, electrical) Knowledge-Based Download PDF

Questions

1. 1.

   A steady electric current passes through a resistive heating element of constant resistance. If the current is doubled, how does the rate at which electrical energy is converted into thermal energy change?

   • A) It remains constant because the electrical resistance of the heating element does not change.
   • B) It doubles because the rate of energy conversion is directly proportional to the current.
   • C) It increases by a factor of eight because thermal energy production scales with the cube of the current.
   • D) It quadruples because the rate of electrical energy conversion is proportional to the square of the current.
2. 2.

   At the microscopic level within a physical system, which statement correctly distinguishes chemical energy from thermal energy?

   • A) Chemical energy is associated with the random kinetic motion of particles, whereas thermal energy is stored as potential energy within chemical bonds.
   • B) Chemical energy is determined strictly by the temperature of the system, whereas thermal energy depends only on the arrangement of atomic nuclei.
   • C) Chemical energy represents the macroscopic work done by the system, whereas thermal energy represents the net electrical charge flowing through it.
   • D) Chemical energy is stored as potential energy in chemical bonds and atomic configurations, whereas thermal energy corresponds to the random microscopic motion of particles.
3. 3.

   In an isolated container, an exothermic chemical reaction takes place with no energy entering or leaving the system. How do the chemical energy, thermal energy, and total energy of the system change as the reaction proceeds?

   • A) Chemical energy decreases and thermal energy increases, while total energy remains constant.
   • B) Chemical energy increases and thermal energy decreases, while total energy remains constant.
   • C) Chemical energy decreases and thermal energy remains constant, while total energy decreases.
   • D) Both chemical energy and thermal energy increase, while total energy remains constant.
4. 4.

   A closed, thermally insulated vessel contains a gas and an electrical resistance coil. When an electric current is passed through the coil, which statement correctly describes the primary energy transformation and its effect on the system?

   • A) Chemical energy is converted into electrical energy, decreasing the temperature of the gas.
   • B) Electrical energy is converted into thermal energy, increasing the internal energy of the gas.
   • C) Thermal energy is converted into chemical energy, keeping the total internal energy of the gas unchanged.
   • D) Electrical energy is converted into mechanical work done on the surroundings, leaving the temperature of the gas unaffected.
5. 5.

   Inside an electrochemical battery during discharge, spontaneous reactions at the electrodes drive an electric current through an external circuit. Which primary energy transformation takes place inside the battery?

   • A) Thermal energy is converted into electrical energy.
   • B) Electrical energy is converted into chemical energy.
   • C) Electrical energy is converted into thermal energy.
   • D) Chemical energy is converted into electrical energy.
6. 6.

   During the thermal decomposition of calcium carbonate in a high-temperature kiln, heat is continuously absorbed to break chemical bonds and form calcium oxide and carbon dioxide. Which primary energy transformation takes place in this reacting system?

   • A) Chemical energy is converted into thermal energy.
   • B) Electrical energy is converted into chemical energy.
   • C) Thermal energy is converted into chemical energy.
   • D) Thermal energy is converted into electrical energy.
7. 7.

   During the complete combustion of a hydrocarbon fuel inside a furnace, which primary energy transformation occurs?

   • A) Chemical energy is converted into thermal energy.
   • B) Thermal energy is converted into chemical energy.
   • C) Electrical energy is converted into thermal energy.
   • D) Chemical energy is converted into electrical energy.
8. 8.

   Which of the following systems directly converts thermal energy into electrical energy?

   • A) A thermocouple generating a potential difference from a temperature gradient across its junctions
   • B) An electric kettle heating water using an electric resistive element
   • C) A dry-cell battery supplying electric current to an external circuit
   • D) A gas furnace burning propane fuel to warm circulating air
9. 9.

   In an electrochemical system performing the electrolysis of water, what primary energy transformation takes place?

   • A) Electrical energy is transformed into chemical potential energy.
   • B) Chemical potential energy is transformed into electrical energy.
   • C) Thermal energy is transformed into electrical energy.
   • D) Mechanical energy is transformed into chemical potential energy.
10. 10.

    When a battery-powered electric heater operates in a room, what is the primary sequence of energy transformations taking place within the system?

    • A) Thermal energy → electrical energy → chemical energy
    • B) Electrical energy → chemical energy → thermal energy
    • C) Chemical energy → electrical energy → thermal energy
    • D) Chemical energy → thermal energy → electrical energy